Functional markers for a *waxy* gene SSR called RM 190, and *waxy* SNPS on intron (In1), exon 6 (Ex6) and exon 10 (Ex10) are used to select for AAC and RVA around the world [93]. The haplotype across these three SNPs in the *waxy* gene (*waxy* SNP haplotypes) have been found to be more efficient in selecting for AAC and RVA than the RM 190 [86, 88]. Across the *waxy* SNP haplotypes (In1-Ex6-Ex10) TAC, GCC, GAC and GAT is highly associated with low AAC, intermediate AAC, high AAC and high AAC accompanied with high RVA paste viscosity.

*BADH2* activity leading to increased levels of 4-aminobutyraldehyde/∆1

no direct role in the synthesis of 2AP [113]. The authors found that ∆1

stories of 2AP synthesis are yet to be fully written".

state without progeny testing.

78 Advances in International Rice Research

varieties from Myanmar [116].

**2.3. Marker-assisted breeding for grain quality in rice**

markers to facilitate selection for specific grain quality types.

By 2050, rice production must double in order to keep pace with population growth. Population growth will come with income growth so consumers will demand even higher quality rice. In addition to this challenge, new biotic and abiotic stresses are merging to due to climate change. Consequently, Rice breeders have to consider a huge number of simple and quantitative traits in combination when developing new lines while, at the same time, maintaining and improving grain quality.

Even though, MAS has been successfully used to improve some biotic, abiotic and quality traits in rice it is based on large effect QTLs/genes and does not take care of epistatic and genetic background effects. Most traits of interest to rice breeders are not controlled only by a few large-effect genes, but by a combination of many genes of small effect and/ or major genes.

Genomic selection (GS) has been projected as alternative to conventional MAS. GS has huge potential to enhance breeding efficiency by increasing gain per selection per unit time [122]. GS breeding allows breeders to select the most desirable parents for the next generation using genome-wide DNA marker data. These parents are selected based on the relationship between the genome-wide markers and phenotypes of the individuals undergoing selection. The major advantage of GS over MAS is that genotyping is not restricted to selected markers that target genes with large effects, but rather all available marker data are used to predict breeding value. This helps to prevent loss of information. Genes with small effect can be tracked and selected for using information on all the marker data. GS would become more effective tool for increasing the efficiency of rice breeding as the costs of genotyping continue to decline [122].

#### **2.5. Conclusion**

Since rice is eaten mainly by humans as whole grain in cooked form, its grain quality is extremely important. The quality of the rice grain can be classified as milling, appearance, cooking and eating as well as nutritional quality. Different consumers around the world demand very specific measurements and combinations of the various aspects of rice grain quality. Breeding for these specific consumer demands can be challenging because grain quality is phenotyped using subjective, biochemical analyses that can be very expensive. Markerassisted selection is thus a very good option for breeding for grain quality. The sequencing of the rice genome over a decade ago has made it possible for researchers to identify genes for the various grain quality traits. Functional molecular markers have been developed that are highly efficient in selecting for grain size, aroma, AAC, GT and paste viscosity parameters. These markers are increasingly being used for breeding for consumer-preferred grain qualities around the world. Modern genome-wide marker technologies which will take care of genes with small effect and allow breeders to simultaneously select for grain quality, yield and stress tolerance are recommended for future rice breeding work.

## **Acknowledgements**

The Alliance for a Green Revolution in Africa (AGRA) funded the author's research on rice grain quality.

## **Author details**

Maxwell Darko Asante

Address all correspondence to<EMAIL_ADDRESS>
Council for Scientific Industrial Research, Crops Research Institute, Kumasi, Ghana

## **References**

[5] Juliano BO. A simplified assay for milled-rice amylose. Cereal Science Today. 1971;16: 334–40,60.

**2.5. Conclusion**

80 Advances in International Rice Research

**Acknowledgements**

grain quality.

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**Author details**

Maxwell Darko Asante

Since rice is eaten mainly by humans as whole grain in cooked form, its grain quality is extremely important. The quality of the rice grain can be classified as milling, appearance, cooking and eating as well as nutritional quality. Different consumers around the world demand very specific measurements and combinations of the various aspects of rice grain quality. Breeding for these specific consumer demands can be challenging because grain quality is phenotyped using subjective, biochemical analyses that can be very expensive. Markerassisted selection is thus a very good option for breeding for grain quality. The sequencing of the rice genome over a decade ago has made it possible for researchers to identify genes for the various grain quality traits. Functional molecular markers have been developed that are highly efficient in selecting for grain size, aroma, AAC, GT and paste viscosity parameters. These markers are increasingly being used for breeding for consumer-preferred grain qualities around the world. Modern genome-wide marker technologies which will take care of genes with small effect and allow breeders to simultaneously select for grain quality, yield

The Alliance for a Green Revolution in Africa (AGRA) funded the author's research on rice

Council for Scientific Industrial Research, Crops Research Institute, Kumasi, Ghana

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**Provisional chapter**

## **Evaluation of Palatability of Cooked Rice**

**Evaluation of Palatability of Cooked Rice**

Ken'ichi Ohtsubo and Sumiko Nakamura Ken'ichi Ohtsubo and Sumiko Nakamura Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/66398

## **Abstract**

Quality evaluations of rice in Japan are performed by sensory testing and physicochemi‐ cal measurements. The former is a basic method that requires large amounts of samples and several panelists. The latter is an indirect method that estimates the eating quality based on the chemical composition, cooking quality, gelatinization properties, and physi‐ cal properties of cooked rice. Satake Co Ltd. developed a taste analyzer in the 1980s that is equipped with a palatability estimation formula that was based on the combination of near‐infrared spectroscopy (NIR) and physicochemical measurements related with sen‐ sory test. A novel method to evaluate the quality of the cooked rice is necessary to breed high‐quality rice cultivars and to select the suitable rice for each consumer and each pur‐ pose. We try to develop the novel method to evaluate the rice quality using various kinds of apparatus, such as Tensipresser, RVA, NIR, and spectrophotometer. Simple, rapid, and accurate method to evaluate the quality of rice grains is very valuable. We evaluated 16 Japanese and Chinese rice cultivars in terms of their physicochemical properties. Based on these quality evaluations, we concluded that Chinese rice cultivars are characterized by a high protein and that the grain texture after cooking has higher hardness and lower stickiness than Japanese ones reflecting the difference in consumers' preference. The relationship between the palatability of rice and agronomical condition to preserve the bio‐diversity for Crested Ibis was investigated. Furthermore, the quality of rice grown in Sado Island, Japan, was assayed using rice grains grown in mountainous areas and in the field areas as samples.

**Keywords:** palatability, physicochemical measurements, cooked rice

## **1. Introduction**

Rice, wheat, and maize are the most important crops in the world. Rice consumers need suf‐ ficient quantities and high‐quality rice grains.

The rice quality depends on various aspects such as consumer safety, nutrition, appearance, price level, and palatability. Because rice is eaten every day, it is indispensable that it should

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

be safe to eat and highly nutritious. Furthermore, because rice provides income for farmers and is prepared, milled, and sold by wholesalers and retailers, the rice yield and price are extremely important to the farmers. Consumers have been asking for more palatable rice because they have recently become more affluent. According to the Food Agency, 45.1% consumers purchase rice grains based on their palatability, 16.3% select it on the basis of its brand name, and 4.8% choose it on the basis of the location of rice production, implying that more than 66% Japanese consumers prefer palatable rice grains to cheaper, nonpalatable rice.

Quality evaluations of rice in Japan are performed by sensory testing and physicochemical mea‐ surements. The former is a basic method that requires large amounts of samples and several panelists. The latter is an indirect method that estimates the eating quality based on the chemical compositions, cooking quality, gelatinization properties, and physical properties of cooked rice.

A rapid, simple, and more accurate method is required to evaluate rice. Therefore, if a novel method that used near‐infrared spectroscopy could be developed, producers and consumers would have a rapid and nondestructive testing method which assessed the quality of the rice grains.

## **2. Sensory test**

Sensory testing is the fundamental method that evaluates the eating quality of rice grains. The members of a trained panel taste cooked rice samples and give scores on the basis of appear‐ ance, flavor, taste, hardness, stickiness, and overall sensory evaluation. The test results can be expressed as numerical values and treated statistically; there are disadvantages to using this test. The results differ depending on the preference of panel members, and the results cannot be directly compared if the time or country differs.

## **3. Physicochemical evaluations**

Physicochemical evaluation [1] is only indirect evaluation of rice palatability, and its results are common all over the world if we use the same method and apparatus. Physicochemical measurements include component analysis, such as protein, amylose, and fibers, pasting prop‐ erties of starch, texture measurements of the cooked rice grains, etc. For the sake of estimating the total palatability, statistical treatment is adopted using the results of each measurement as the variables. Multiple regression analysis, principal component analysis, and PLS analysis are very useful to clarify the characteristics of the rice samples. Recently, spectrophotometric analy‐ ses, such as NIR or visible‐light spectrometer, are utilized to estimate the chemical components and to develop the estimation formulae for palatability. "Taste Analyzer" is an example of the NIR system as a nondestructive estimation apparatus for palatability of rice grains. Examples of sensory test and physicochemical evaluation of rice palatability are shown in **Table 1**.

## **3.1. Amylose content**

Amylose content is the most important factor that determines rice quality because starch shares approximately 85% (w/w, dry basis) of the milled rice grains. Because Japanese con‐

**Table 1.** Evaluation of rice palatability.

sumers prefer soft and sticky cooked rice, low amylose rice is the dominant rice sold in the Japanese rice market. Amylose content is generally measured by the colorimetric method of Juliano [2].

#### **3.2. Protein content**

be safe to eat and highly nutritious. Furthermore, because rice provides income for farmers and is prepared, milled, and sold by wholesalers and retailers, the rice yield and price are extremely important to the farmers. Consumers have been asking for more palatable rice because they have recently become more affluent. According to the Food Agency, 45.1% consumers purchase rice grains based on their palatability, 16.3% select it on the basis of its brand name, and 4.8% choose it on the basis of the location of rice production, implying that more than 66% Japanese consumers prefer palatable rice grains to cheaper, nonpalatable rice. Quality evaluations of rice in Japan are performed by sensory testing and physicochemical mea‐ surements. The former is a basic method that requires large amounts of samples and several panelists. The latter is an indirect method that estimates the eating quality based on the chemical compositions, cooking quality, gelatinization properties, and physical properties of cooked rice. A rapid, simple, and more accurate method is required to evaluate rice. Therefore, if a novel method that used near‐infrared spectroscopy could be developed, producers and consumers would have a rapid and nondestructive testing method which assessed the quality of the rice

Sensory testing is the fundamental method that evaluates the eating quality of rice grains. The members of a trained panel taste cooked rice samples and give scores on the basis of appear‐ ance, flavor, taste, hardness, stickiness, and overall sensory evaluation. The test results can be expressed as numerical values and treated statistically; there are disadvantages to using this test. The results differ depending on the preference of panel members, and the results cannot

Physicochemical evaluation [1] is only indirect evaluation of rice palatability, and its results are common all over the world if we use the same method and apparatus. Physicochemical measurements include component analysis, such as protein, amylose, and fibers, pasting prop‐ erties of starch, texture measurements of the cooked rice grains, etc. For the sake of estimating the total palatability, statistical treatment is adopted using the results of each measurement as the variables. Multiple regression analysis, principal component analysis, and PLS analysis are very useful to clarify the characteristics of the rice samples. Recently, spectrophotometric analy‐ ses, such as NIR or visible‐light spectrometer, are utilized to estimate the chemical components and to develop the estimation formulae for palatability. "Taste Analyzer" is an example of the NIR system as a nondestructive estimation apparatus for palatability of rice grains. Examples of

sensory test and physicochemical evaluation of rice palatability are shown in **Table 1**.

Amylose content is the most important factor that determines rice quality because starch shares approximately 85% (w/w, dry basis) of the milled rice grains. Because Japanese con‐

grains.

**2. Sensory test**

92 Advances in International Rice Research

**3.1. Amylose content**

be directly compared if the time or country differs.

**3. Physicochemical evaluations**

Protein content is another extremely important factor that determines rice quality. Cooked rice with high protein content tends to be hard and nonsticky. Protein content is measured by the Kieldahl or the combustion method.

#### **3.3. Moisture content**

Moisture content affects the eating quality of cooked rice. Low‐moisture rice grains absorb water faster than high‐moisture grains. In cooked rice, the final moisture content from the low‐moisture rice grains is higher than that from the high‐moisture rice grains. Moisture con‐ tent is generally measured by the oven dry method.

**Figure 1.** Rapid visco analyzer.

## **3.4. Gelatinization properties**

The maximum viscosity, final viscosity, and "break‐down" viscosity (maximum viscosity‐ minimum viscosity) are measured in an Amylograph. These viscosity measurements were considered good indices for the eating quality of rice. The Rapid‐Visco‐Analyzer (RVA) was developed in Australia and was recently introduced in Japan (**Figure 1**) [3]. Time (13–19 min) and samples (3.5 g) can be saved using an RVA.

## **3.5. Fat acidity**

Fat acidity is a good index to measure the quality deterioration of rice grains during storage. In Japan, newly harvested rice is preferred to aged rice because consumers like soft and sticky cooked rice. Ohtsubo proposed a new colorimetric method to accurately measure fat acidity [4].

## **3.6. Cooking quality test**

A cooking quality test was developed by the researchers of USDA in the 1950s [5]. An expanded volume and water uptake ratios are measured after cooking rice samples in excess amounts of water. Dissolved amylose is measured by color generation by combining iodine and amylose.

## **3.7. Physical properties of cooked rice grains**

Physical properties of cooked rice grains, such as hardness and stickiness, are measured by a Texturometer, Tensipresser, Texture analyzer, or Rheolograph‐micro. Low‐compression and high‐compression test using a Tensipresser [6] is shown in **Figure 2**.

### **3.8. Palatability estimation formula**

Chikubu et al. developed a new equation to estimate the palatability of rice grains using a multiple regression analysis based on physicochemical measurements, such as an amylo‐ graph viscosity profile, protein assay, and iodine blue value measurements [7]. The formula showed a high correlation between the results of a sensory test (*R* = 0.84) of the rice samples harvested next year.

#### **3.9. Application of near‐infrared spectroscopy to evaluate rice quality**

Near‐infrared spectroscopy is a rapid, nondestructive, and extremely promising technique to evaluate qualities of the rice grains. In Japan, NIR spectroscopy was initially used to deter‐ mine the protein and moisture content of the rice flours. Satake Co. Ltd subsequently com‐ bined NIR and palatability estimation formula and developed a new system called "Taste Analyzer."

#### *3.9.1. Protein content*

Iwamoto et al. reported that NIR was equally sensitive to both rice and wheat proteins. A stan‐ dard error of estimation (SEP) was decreased for calibrations using a derivative absorbance.

**Figure 2.** Tensipresser used for texture measurement of cooked rice grains.

**3.4. Gelatinization properties**

94 Advances in International Rice Research

**3.5. Fat acidity**

**3.6. Cooking quality test**

iodine and amylose.

harvested next year.

Analyzer."

*3.9.1. Protein content*

and samples (3.5 g) can be saved using an RVA.

**3.7. Physical properties of cooked rice grains**

**3.8. Palatability estimation formula**

high‐compression test using a Tensipresser [6] is shown in **Figure 2**.

**3.9. Application of near‐infrared spectroscopy to evaluate rice quality**

The maximum viscosity, final viscosity, and "break‐down" viscosity (maximum viscosity‐ minimum viscosity) are measured in an Amylograph. These viscosity measurements were considered good indices for the eating quality of rice. The Rapid‐Visco‐Analyzer (RVA) was developed in Australia and was recently introduced in Japan (**Figure 1**) [3]. Time (13–19 min)

Fat acidity is a good index to measure the quality deterioration of rice grains during storage. In Japan, newly harvested rice is preferred to aged rice because consumers like soft and sticky cooked rice. Ohtsubo proposed a new colorimetric method to accurately measure fat acidity [4].

A cooking quality test was developed by the researchers of USDA in the 1950s [5]. An expanded volume and water uptake ratios are measured after cooking rice samples in excess amounts of water. Dissolved amylose is measured by color generation by combining

Physical properties of cooked rice grains, such as hardness and stickiness, are measured by a Texturometer, Tensipresser, Texture analyzer, or Rheolograph‐micro. Low‐compression and

Chikubu et al. developed a new equation to estimate the palatability of rice grains using a multiple regression analysis based on physicochemical measurements, such as an amylo‐ graph viscosity profile, protein assay, and iodine blue value measurements [7]. The formula showed a high correlation between the results of a sensory test (*R* = 0.84) of the rice samples

Near‐infrared spectroscopy is a rapid, nondestructive, and extremely promising technique to evaluate qualities of the rice grains. In Japan, NIR spectroscopy was initially used to deter‐ mine the protein and moisture content of the rice flours. Satake Co. Ltd subsequently com‐ bined NIR and palatability estimation formula and developed a new system called "Taste

Iwamoto et al. reported that NIR was equally sensitive to both rice and wheat proteins. A stan‐ dard error of estimation (SEP) was decreased for calibrations using a derivative absorbance. However, the derivative procedure may possibly make an increment bias in cases that predict "unknown" samples [8]. Inatsu utilized NIR spectroscopy to select palatable rice cultivars by measuring the protein content of rice because low protein rice is preferred in Japan because of their palatability [9].

## *3.9.2. Estimation of rice amylose contents by NIR [10]*

Japanese rice breeders have tried to develop palatable rice cultivars by selecting low amylose rice; however, the amylose content among Japanese rice grains are not significantly different (15–20%). NIR spectroscopy can easily compare protein and moisture; however, it does not easily differentiate amylose from amylopectin. Villareal and Delwiche had already developed excellent calibrations to detect amylose in various rice samples through NIR spectroscopy [11, 12]. Japanese consumers request high‐performance calibration for the measurement of narrow range amylose of Japanese rice cultivars. Apparent amylose content (AAC) analysis is a rapid and simple technique that uses NIT spectroscopy. It was developed based on the near‐infrared transmission spectra and the reference value of AAC determined by the iodine colorimetric method. The wide AAC range (0–35.3%) PLS model was inadequate for the accurate predic‐ tion of the extremely narrow range of the AAC (13.2–20.7%) of Japanese milled rice samples. The statistics performed on the 11‐factor PLS model for the extremely narrow range of AAC analyses was 0.78, 0.74, and 2.01 in SECv, r2 , and RPD, respectively. The performance of this model was 1.25 and 0.49 for SEP and r², respectively, on the validation set. The previous models developed a wide range of AAC samples, which were difficult to apply to the narrow range of AAC rice. The present AAC analysis technique is based on NIT spectroscopy, which can discriminate between the extremely narrow differences in AAC of Japanese milled rice in the same subfamily.

#### *3.9.3. Eating quality evaluation system by NIR*

Satake Co. Ltd. developed a taste analyzer in the 1980s that combined the palatability esti‐ mation formula that was based on the physicochemical measurements and NIR. The taste analyzer principle is based on the multiple regression analysis that uses NIR data (protein, moisture, amylose, and fat acidity) against the sensory test results. A previous study by the Japanese Association of Milling Companies evaluated three different types of palatability evaluation system using NIR. The results showed that the taste scores correlated significantly with the results of the sensory test (*r* = 0.54–0.63), but the scores were affected by the moisture contents and milling yield [13].

There were eight Japanese companies that developed the characteristic systems to evaluate the palatability of rice grains based on the spectroscopic technique. More than 1000 agri‐ cultural cooperatives, wholesalers, and retailers introduced these NIR systems to evaluate the quality of their rice grains (**Figure 3**). In 1996, the Japanese Food Agency conducted a survey regarding the palatability evaluation system, and the results showed that 67% users were satisfied with the performance of the system. The protein and moisture data was extremely reliable, but some users requested an improvement in the taste score and amylose accuracy.

**Figure 3.** Taste analyzer based upon NIR technology.

## **4. Proposal as novel physicochemical measurement, iodine colorimetric analysis, for rice palatability evaluation [14]**

## **4.1. Introduction**

*3.9.3. Eating quality evaluation system by NIR*

contents and milling yield [13].

96 Advances in International Rice Research

**Figure 3.** Taste analyzer based upon NIR technology.

amylose accuracy.

Satake Co. Ltd. developed a taste analyzer in the 1980s that combined the palatability esti‐ mation formula that was based on the physicochemical measurements and NIR. The taste analyzer principle is based on the multiple regression analysis that uses NIR data (protein, moisture, amylose, and fat acidity) against the sensory test results. A previous study by the Japanese Association of Milling Companies evaluated three different types of palatability evaluation system using NIR. The results showed that the taste scores correlated significantly with the results of the sensory test (*r* = 0.54–0.63), but the scores were affected by the moisture

There were eight Japanese companies that developed the characteristic systems to evaluate the palatability of rice grains based on the spectroscopic technique. More than 1000 agri‐ cultural cooperatives, wholesalers, and retailers introduced these NIR systems to evaluate the quality of their rice grains (**Figure 3**). In 1996, the Japanese Food Agency conducted a survey regarding the palatability evaluation system, and the results showed that 67% users were satisfied with the performance of the system. The protein and moisture data was extremely reliable, but some users requested an improvement in the taste score and As described in Section 3, physicochemical test is very important because it is time‐saving and labor‐saving objective test for rice palatability. Main component of rice grains is starch, there‐ fore, amylose content affects eating quality [15]. Low‐amylose rice generally becomes soft and sticky after cooking, whereas high‐amylose rice becomes hard with fluffy separated grains [16].

The most widely used method for amylose determination is a colorimetric assay where iodine binds with amylose to produce a blue‐purple color, which is measured spectrophotometri‐ cally at a single wavelength (620 nm) [2].

We here characterized the starch of various rice cultivars; evaluated the relationship between their iodine absorption curve and apparent amylose contents, amylopectin fractions, and resistant starch. We improved the iodine colorimetric method, and developed the novel estimation formulae against the amylose contents, resistant starch, or a certain fractions of definite chain‐length amylopectin. This novel method would lead to an easy and low‐cost spectroscopic method for analyses of starch characteristics.

## **4.2. Contents**

We used Japonica rice, Iindica rice, Indica‐Japonica hybrid rice, *ae* mutant rice, and waxy rice produced in Japan and China.

We polished brown rice to a milling yield of 90–91%, using an experimental friction‐type rice milling machine (Yamamotoseisakusyo, Co. Ltd., Tendoh, Japan). White rice flour was produced with a cyclone mill (SFC‐S1; Udy, Fort Collins, CO, USA). Starch granules were prepared from polished rice flour using the cold alkali method.

The iodine absorption spectrum of the rice starch was measured using a Shimadzu UV‐1800 spectrophotometer. The AAC of rice starch was measured by the iodine colorimetric method of Juliano [2]. The iodine absorption spectrum was scanned from 200 to 900 nm. The absor‐ bance was measured at 620 nm, at *λ*max (wavelength at the peak between 400 and 900 nm), and absorbance at *λ*max (*Aλ*max) (**Figure 4**).

The area of F1 (from B to 400 nm), area of F2 (from 400 nm to *λ*max), and area of F3 (from *λ*max to 900 nm) were calculated.

We developed a formula for apparent amylose content based on iodine colorimetric analysis. Estimation formula is as follows:

$$\text{AAC} = 73.31 \times A \,\lambda\_{\text{max}} + 0.11 \times \lambda\_{\text{max}} - 73.02 \tag{1}$$

**Figure 4.** Analysis of iodine absorption curve of various starch samples.

Chain length distribution (CD) was carried out by the method of Hanashiro et al. using HPAEC‐PAD of isoamylase‐debranched materials of starch:

$$F\theta 3 = 44.69 \times A \,\lambda\_{\text{max}} - 0.77 \tag{2}$$

RS in the starch of rice flour was measured according to the AOAC method using a RS assay kit (Megazyme, Wicklow, Ireland) in which each sample (100 mg) was digested by pancreatin and amyloglucosidase at 37°C for 6 h, followed by the measurement of glucose at 510 nm:

$$\text{RS} = \text{21.31} \times A \,\lambda\_{\text{max}} - 0.030 \times \lambda\_{\text{max}} + 12.25 \tag{3}$$

Fraction of DP10 (short chain glucans of amylopectin) and fraction of DP22 (medium chain glucans of amylopectin) were estimated based on F2 area and *Aλ*max based on the iodine colo‐ rimetric analyses, respectively, as shown in **Figure 5**.

#### **4.3. Conclusion**

We found that the iodine absorption curve differed between the Indica rice, Japonica rice, Japonica‐Indica hybrid rice, *ae* mutant rice cultivars, and glutinous rice cultivars. We propose a novel index, "new *λ*max" based on iodine absorption curve, which shows higher correlation with amylose, resistant starch, or CD of amylopectin than ordinary *λ*max.

**Figure 5.** Estimation of fraction DP10 and fraction DP22 based on iodine colorimetric analyses.

Chain length distribution (CD) was carried out by the method of Hanashiro et al. using

*Fb*3 = 44.69 × *A λmax* –0.77 (2)

RS in the starch of rice flour was measured according to the AOAC method using a RS assay kit (Megazyme, Wicklow, Ireland) in which each sample (100 mg) was digested by pancreatin and amyloglucosidase at 37°C for 6 h, followed by the measurement of glucose at 510 nm:

*RS* = 21.31 × *A λ*max –0.030 × *λ*max + 12.25 (3)

Fraction of DP10 (short chain glucans of amylopectin) and fraction of DP22 (medium chain glucans of amylopectin) were estimated based on F2 area and *Aλ*max based on the iodine colo‐

We found that the iodine absorption curve differed between the Indica rice, Japonica rice, Japonica‐Indica hybrid rice, *ae* mutant rice cultivars, and glutinous rice cultivars. We propose a novel index, "new *λ*max" based on iodine absorption curve, which shows higher correlation with amylose, resistant starch, or CD of amylopectin than ordinary *λ*max.

HPAEC‐PAD of isoamylase‐debranched materials of starch:

**Figure 4.** Analysis of iodine absorption curve of various starch samples.

98 Advances in International Rice Research

rimetric analyses, respectively, as shown in **Figure 5**.

**4.3. Conclusion**

We developed the novel estimation formulae for AAC, RS contents, amylopectin chain lengths (Fa; DP ≦ 12, Fb3; DP≦ 37), and fraction of DP10 (short chain glucans of amylopectin) and fraction of DP22 (medium chain glucans of amylopectin) on the basis of the iodine absorp‐ tion curve. These formulae would lead to an easy and low‐cost spectroscopic method for the starch characteristics.

## **5. Examples of physicochemical measurements of rice palatability**

#### **5.1. Comparison of physicochemical properties between Japanese and Chinese rice cultivars**

As described in Section 3, in the case of physicochemical evaluation, we can get the common results for the rice samples produced in different countries if we use the same method. As an example, we report the results of physicochemical measurements of rice palatability using rice samples produced in Japan and China.

## *5.1.1. Introduction*

China is the largest rice‐producing country, accounting for 32% of the global production from 20% of the global rice‐growing area. China produces Indica subspecies mainly in the southern region and Japonica subspecies mainly in the northern region (Heilongjiang, Liaoning), and eastern or southern region (Jilin, Jiangsu, Zhejiang, and Yunnan), whereas the other three countries, India, Indonesia, and Bangladesh, primarily grow Indica rice. In China, consum‐ ers are now choosing Japonica rice based on its shape and color as well as its texture and taste. Zhang et al. performed a sensory test of Chinese Japonica rice cultivars [17], in which a Chinese panel mainly determined the overall eating quality based on the stickiness and hard‐ ness. In the present section, we conducted physicochemical evaluations of some Chinese and Japanese Japonica rice cultivars using traditional and novel indicators based on the iodine absorption curve and RVA.

## *5.1.2. Materials and methods*

We used high‐quality premium Japanese Japonica rice (Koshihikari, Tsuyahime, Yumepirika, Sagabiyori, and Kinumusume) and Chinese Japonica rice cultivars (Kenjing 5, Shendao 529, Jinyuan 45, Changyou 5, Lianjing 7, Longjing 31, Nanjing 9108, Jinongda 878, Shennong 265, Daohuaxiang, and Jinchuan 1) as rice samples.

## *<IP_ADDRESS>. Measurement of the moisture content of rice flour*

The moisture content of the milled rice grains was measured using an oven‐drying method by drying 2 g flour samples for 1 h at 135°C.

## *<IP_ADDRESS>. Protein content*

Nitrogen was determined using a nitrogen analyzer based on the combustion method. The protein content was obtained by multiplying a nitrogen‐protein conversion factor of 5.95.

## *<IP_ADDRESS>. Measurement of iodine absorption spectra*

The iodine absorption spectrum of milled rice was measured using a Shimadzu UV‐1800 spectrophotometer. The apparent amylose content (AAC) of milled rice was estimated using the iodine colorimetric method (as described by Juliano [2]). The iodine absorption spectrum [14] was analyzed from 200 to 900 nm using a square cell of which inner dimension was 1 cm × 1 cm.

## *<IP_ADDRESS>. Measurement of pasting properties of rice flours*

The pasting properties of starch rice flours were analyzed using an RVA (model Super 4; Newport Scientific Pty Ltd, Warriewood, Australia). A programmed heating and cooling con‐ dition was followed as described by Toyoshima et al. [3]. Novel indices, such as the setback/ consistency (SB/Con) and maximum viscosity/minimum viscosity (Max/Fin) ratios, have very strong correlations with the proportion of intermediate and long chains of amylopectin: Fb1 + 2 + 3 (DP≧ 13) [14].

## *<IP_ADDRESS>. Physical properties of boiled rice grains*

*5.1.1. Introduction*

100 Advances in International Rice Research

absorption curve and RVA.

*5.1.2. Materials and methods*

*<IP_ADDRESS>. Protein content*

Fb1 + 2 + 3 (DP≧ 13) [14].

× 1 cm.

Daohuaxiang, and Jinchuan 1) as rice samples.

drying 2 g flour samples for 1 h at 135°C.

*<IP_ADDRESS>. Measurement of iodine absorption spectra*

*<IP_ADDRESS>. Measurement of pasting properties of rice flours*

*<IP_ADDRESS>. Measurement of the moisture content of rice flour*

China is the largest rice‐producing country, accounting for 32% of the global production from 20% of the global rice‐growing area. China produces Indica subspecies mainly in the southern region and Japonica subspecies mainly in the northern region (Heilongjiang, Liaoning), and eastern or southern region (Jilin, Jiangsu, Zhejiang, and Yunnan), whereas the other three countries, India, Indonesia, and Bangladesh, primarily grow Indica rice. In China, consum‐ ers are now choosing Japonica rice based on its shape and color as well as its texture and taste. Zhang et al. performed a sensory test of Chinese Japonica rice cultivars [17], in which a Chinese panel mainly determined the overall eating quality based on the stickiness and hard‐ ness. In the present section, we conducted physicochemical evaluations of some Chinese and Japanese Japonica rice cultivars using traditional and novel indicators based on the iodine

We used high‐quality premium Japanese Japonica rice (Koshihikari, Tsuyahime, Yumepirika, Sagabiyori, and Kinumusume) and Chinese Japonica rice cultivars (Kenjing 5, Shendao 529, Jinyuan 45, Changyou 5, Lianjing 7, Longjing 31, Nanjing 9108, Jinongda 878, Shennong 265,

The moisture content of the milled rice grains was measured using an oven‐drying method by

Nitrogen was determined using a nitrogen analyzer based on the combustion method. The protein content was obtained by multiplying a nitrogen‐protein conversion factor of 5.95.

The iodine absorption spectrum of milled rice was measured using a Shimadzu UV‐1800 spectrophotometer. The apparent amylose content (AAC) of milled rice was estimated using the iodine colorimetric method (as described by Juliano [2]). The iodine absorption spectrum [14] was analyzed from 200 to 900 nm using a square cell of which inner dimension was 1 cm

The pasting properties of starch rice flours were analyzed using an RVA (model Super 4; Newport Scientific Pty Ltd, Warriewood, Australia). A programmed heating and cooling con‐ dition was followed as described by Toyoshima et al. [3]. Novel indices, such as the setback/ consistency (SB/Con) and maximum viscosity/minimum viscosity (Max/Fin) ratios, have very strong correlations with the proportion of intermediate and long chains of amylopectin: The boiled rice samples were kept in the vessel at 25°C for 2 h and then subjected to the measurements. The hardness and stickiness of the boiled rice grains were measured using a Tensipresser (My Boy System, Taketomo Electric Co., Tokyo, Japan) using "low compression (25%) and high compression (90%) test" [6]. The average of each parameter was calculated by measuring 20 individual grains. As a staling test of the cooked rice, the cooked samples were stored at 10°C for 16 h and measured again with a Tensipresser according to the previously described method [6].

## *<IP_ADDRESS>. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE)*

Proteins were extracted from milled rice flour samples (0.5 g) by shaking with 2 mL of buf‐ fer A (50 mM Tris‐HCl, pH 6.8, 2% SDS, 5% 2‐mercaptoethanol) at 37°C for 30 min and then centrifuged for 5 min at 3000 × *g*. The supernatant (1 mL) was diluted with an equal volume of sample buffer (0.125 M Tris‐HCl, pH 6.8, 10% 2‐mercaptoethanol, 4% SDS, 10% sucrose, 0.004% bromophenol blue) and mixed well, followed by heating for 2 min at 100°C. In total 10 μg of extracted protein was charged into each lane. SDS‐PAGE was conducted with a 12% polyacrylamide gel according to the modified method described by Laemmli [18]. The values were calculated based on the intensities of various bands on the gel after SDS‐PAGE analysis using the ATTO densitograph software library (CS Analyzer ver 3.0).

#### *5.1.3. Results and discussion*

## *<IP_ADDRESS>. Main chemical components*

Protein is a very important component of milled rice, and it affects the physical properties of cooked rice grains. Higher protein content makes the rice grains harder and less sticky. The protein content of milled Japonica rice is around 6.5%. The protein contents of Chinese rice cultivars (6.8–9.0%; mean = 7.8%) were significantly higher than those of Japanese rice variet‐ ies (6.2–6.8%; mean = 6.5%).

AAC has been used as a good parameter for estimating the cooking or eating quality of rice grains, and the iodine colorimetric method for AAC measurement at 620 nm was developed by Juliano [2]. AAC comprises a large amount of amylose and a small amount of SLC in amylopectin. In general, low amylose rice becomes soft and sticky after cooking, whereas high amylose rice becomes hard and separated. The AAC values for Chinese rice cultivars (6.6–17.2%; mean = 14.3%) were higher than those of Japanese rice cultivars (9.7–14.6%; mean = 12.7%). In our previous study [14], we showed that the iodine absorption curve differed among various samples of rice cultivars, and we developed a novel formula for estimating AAC. (AAC = 73.31 × *Aλ*max + 0.11 × *λ*max – 73.02). It was shown that a multiple coefficient of determination of 0.996 was obtained when we used this formula to estimate AAC for Chinese rice cultivars.

The molecular structures of many starches, including the molecular sizes of amylose and the amylopectin branch chain lengths, have been reported previously [19–22]. The high molecu‐ lar weight amyloses tend to have a longer wavelength for *λ*max. We found that the glutinous rice cultivars had very low *λ*max values, and Indica rice, Japonica‐Indica hybrid rice cultivars, and a high‐amylose Japonica rice cultivar had higher *λ*max values. The *λ*max values of Japonica rice cultivars were intermediate [14].

The "new *λ*max" values are assumed to be related to the SLC content of amylopectin [14]. It was shown that the "new *λ*max" values of the Chinese rice cultivars (0.11–0.27; mean = 0.23) were lower than those of the Japanese rice cultivars (0.23–0.26; mean = 0.25).

The starches in the rice cultivars grown under low temperatures have a significantly higher amylose contents than those of the rice cultivars grown under high temperature, whereas the SLC contents of the amylopectin were lower [23–27]. Thus, we consider that the starch properties of Japanese rice cultivars were influenced by the ambient temperatures during the development of the grain, which yielded high "new *λ*max" values.

## *<IP_ADDRESS>. Physical properties of cooked rice grains*

There were differences in the values of physical properties of the cooked rice grains. The balance of ‐H1/H1, ‐H2/H2, A3/A1, and A6/A4 are important indices when evaluating the palatability of rice [16].

The hardness of the surface layer (H1) was higher in the Chinese rice cultivars than the Japanese rice varieties, and the hardness of the overall layer (H2) of Chinese rice cultivars was higher than that of the Japanese rice varieties. The stickiness of the surface layer (‐H1) was significantly lower in the Chinese rice cultivars than the Japanese rice cultivars, whereas the stickiness of overall layer (‐H2) was higher in the Chinese rice varieties than the Japanese rice cultivars. The balance degree of the surface layer (‐H1/H1) was significantly lower in the Chinese rice varieties than the Japanese rice varieties, and that of the surface layer (A3/A1) was significantly lower in the Chinese rice varieties than the Japanese rice varieties.

Low amylose rice cultivars are stale‐resistant according to Takami et al., who previously reported the staling characteristics of cooked low amylose rice [28]. In the staling test, we stored the cooked rice at 10°C for 16 h (**Figure 6**). The staling rate for starch based on the surface layer hardness (H1) was significantly higher in the Chinese rice cultivars than the Japanese rice cultivars. In particularly, Jinongda 878 (2.3 times), Daohuaxiang (1.9 times), and Nanjing 9108 (1.9 times) had very high values. The staling rates for starch based on the hard‐ ness of the overall layer (H2) were almost the same in the Chinese and Japanese rice cultivars. The staling rate for starch based on the hardness of the surface layer (H1) in Chinese rice varieties had a positive correlation with the intensities of the 13 kDa prolamin spots and the protein content at *p* < 0.01.

## *<IP_ADDRESS>. SDS‐PAGE*

The intensities of the bands of 13 kDa prolamin were correlated positively with *λ*max/*Aλ*max (*r* = 0.66) and "new *λ*max" (*r* = 0.65) in Chinese rice varieties, and with the glutamic acid (*r* = 0.85), whereas with *λ*max (*r* = ‐0.65) had negative correlation.

**Figure 6.** Results of the staling starch test of the physical properties of cooked rice grains.

The rice seed storage proteins mainly comprise glutelins and prolamins. PB‐I is highly enriched with prolamin and it constitutes approximately 20% of the milled rice protein con‐ tents. PB‐II mainly contains glutelins and it constitutes 60–65% of the milled rice protein [29]. The protein content of rice grains is influenced by the weather conditions, as it is increased by high air temperature or high water temperature, but decreased by low water temperature or sun shading during the ripening stage [30]. Matsui et al. [31] showed that the Final vis. and Cons values of near‐isogenic line pairs for the low glutelin gene (*Lgc1*) locus were significantly higher in low glutelin lines, and the surface stickiness was also significantly lower in the low glutelin lines. Protein production also tended to increase with higher levels of nitrogenous fertilizer at any planting density [32].

#### *5.1.4. Conclusion*

rice cultivars had very low *λ*max values, and Indica rice, Japonica‐Indica hybrid rice cultivars, and a high‐amylose Japonica rice cultivar had higher *λ*max values. The *λ*max values of Japonica

The "new *λ*max" values are assumed to be related to the SLC content of amylopectin [14]. It was shown that the "new *λ*max" values of the Chinese rice cultivars (0.11–0.27; mean = 0.23) were

The starches in the rice cultivars grown under low temperatures have a significantly higher amylose contents than those of the rice cultivars grown under high temperature, whereas the SLC contents of the amylopectin were lower [23–27]. Thus, we consider that the starch properties of Japanese rice cultivars were influenced by the ambient temperatures during the

There were differences in the values of physical properties of the cooked rice grains. The balance of ‐H1/H1, ‐H2/H2, A3/A1, and A6/A4 are important indices when evaluating the

The hardness of the surface layer (H1) was higher in the Chinese rice cultivars than the Japanese rice varieties, and the hardness of the overall layer (H2) of Chinese rice cultivars was higher than that of the Japanese rice varieties. The stickiness of the surface layer (‐H1) was significantly lower in the Chinese rice cultivars than the Japanese rice cultivars, whereas the stickiness of overall layer (‐H2) was higher in the Chinese rice varieties than the Japanese rice cultivars. The balance degree of the surface layer (‐H1/H1) was significantly lower in the Chinese rice varieties than the Japanese rice varieties, and that of the surface layer (A3/A1) was significantly lower in the Chinese rice varieties than the Japanese rice

Low amylose rice cultivars are stale‐resistant according to Takami et al., who previously reported the staling characteristics of cooked low amylose rice [28]. In the staling test, we stored the cooked rice at 10°C for 16 h (**Figure 6**). The staling rate for starch based on the surface layer hardness (H1) was significantly higher in the Chinese rice cultivars than the Japanese rice cultivars. In particularly, Jinongda 878 (2.3 times), Daohuaxiang (1.9 times), and Nanjing 9108 (1.9 times) had very high values. The staling rates for starch based on the hard‐ ness of the overall layer (H2) were almost the same in the Chinese and Japanese rice cultivars. The staling rate for starch based on the hardness of the surface layer (H1) in Chinese rice varieties had a positive correlation with the intensities of the 13 kDa prolamin spots and the

The intensities of the bands of 13 kDa prolamin were correlated positively with *λ*max/*Aλ*max (*r* = 0.66) and "new *λ*max" (*r* = 0.65) in Chinese rice varieties, and with the glutamic acid (*r* =

0.85), whereas with *λ*max (*r* = ‐0.65) had negative correlation.

lower than those of the Japanese rice cultivars (0.23–0.26; mean = 0.25).

development of the grain, which yielded high "new *λ*max" values.

rice cultivars were intermediate [14].

102 Advances in International Rice Research

*<IP_ADDRESS>. Physical properties of cooked rice grains*

palatability of rice [16].

protein content at *p* < 0.01.

*<IP_ADDRESS>. SDS‐PAGE*

varieties.

In this study, we evaluated 16 Japanese and Chinese rice cultivars in terms of their main chemical components, iodine absorption curve, apparent amylose content (AAC), pasting property, resistant starch content, physical properties, and SDS‐PAGE.

Based on these quality evaluations, we can conclude that Chinese rice cultivars are character‐ ized by their high protein content. The hardness of the surface layer (H1) and overall layer (H2) were higher in the Chinese rice cultivars than the Japanese rice cultivars, whereas the stickiness of the surface layer, and the balance degree of the surface layer were lower in the Chinese rice cultivars than the Japanese rice cultivars, although the stickiness of the overall layer (‐H2) was higher in the Chinese rice cultivars than the Japanese rice cultivars. In addition, the texture of cooked rice was strongly correlated with the iodine absorption factors.

In a previous study, we developed a novel formula for estimating AAC based on the iodine absorption curve. The validation test showed a determination coefficient of 0.996 for estimat‐ ing AAC of Chinese rice cultivars as unknown samples.

## **5.2. Palatability evaluation of the Japanese premium rice "Koshihikari" in Sado Island**

As described in Section 3, in the case of physicochemical evaluation, we can get the common results for the rice samples produced in the different regions if we use the same method. As an example, we report the results of physicochemical measurements of rice palatability using rice samples produced by the different cultivation conditions, and rice samples grown in the mountainous region and the field region in Sado Island, Japan.

## *5.2.1. Introduction*

Rice is one of the most important staple foods in the world. "Koshihikari" is the most famous premium rice cultivar, and it shares about 37% of all rice production in Japan. "Koshihikari" is cultivated all over Japan, but that grown in Niigata Prefecture is considered the best "Koshihikari" in Japan with regards to its quality and quantity. Sado Island is part of the Niigata Prefecture and the "Koshihikari" cultivated in Sado, Iwafune, and Uonuma is evalu‐ ated as the highest quality rice.

Sado Island is located off the Niigata City seashore and it is the second largest island in Japan after Okinawa Island. Sado Island is famous for its Toki (crested ibis, *Nipponia nippon*), which is an endangered species in Japan. The inhabitants of Sado city and its farmers are trying to make an ideal habitat for Toki. The feed for Toki are small fish and insects, such as the loach, grasshoppers, and worms as well as small river crabs, and frogs. The farmers are making an effort to keep the environment agriculturally sound to protect the ibis from extinction.

Sado city awards the farmers a harmonizing environment certificate known as the "homeland to live with crested ibis" if the farmers adopt an ibis‐friendly agricultural method. Farmers create a narrow pond, preserve bio‐diversity with winter‐flooding, and reduce the use of chemical fertilizers and agricultural chemicals by over 50% compared with conventional cultivation.

However, the effects of this ibis‐friendly agricultural method, which also include abolish‐ ing drying paddy field after transplanting, does not equate to palatability of the rice grains. Therefore, the relationship between the palatability of rice and agronomical condition to pre‐ serve the bio‐diversity for ibis was investigated. Furthermore, the quality of rice grown in Sado Island was compared with that of rice grown in mountainous areas and in the field.

## *5.2.2. Materials and methods*

(H2) were higher in the Chinese rice cultivars than the Japanese rice cultivars, whereas the stickiness of the surface layer, and the balance degree of the surface layer were lower in the Chinese rice cultivars than the Japanese rice cultivars, although the stickiness of the overall layer (‐H2) was higher in the Chinese rice cultivars than the Japanese rice cultivars. In addition, the texture of cooked rice was strongly correlated with the iodine absorption

In a previous study, we developed a novel formula for estimating AAC based on the iodine absorption curve. The validation test showed a determination coefficient of 0.996 for estimat‐

**5.2. Palatability evaluation of the Japanese premium rice "Koshihikari" in Sado Island**

As described in Section 3, in the case of physicochemical evaluation, we can get the common results for the rice samples produced in the different regions if we use the same method. As an example, we report the results of physicochemical measurements of rice palatability using rice samples produced by the different cultivation conditions, and rice samples grown in the

Rice is one of the most important staple foods in the world. "Koshihikari" is the most famous premium rice cultivar, and it shares about 37% of all rice production in Japan. "Koshihikari" is cultivated all over Japan, but that grown in Niigata Prefecture is considered the best "Koshihikari" in Japan with regards to its quality and quantity. Sado Island is part of the Niigata Prefecture and the "Koshihikari" cultivated in Sado, Iwafune, and Uonuma is evalu‐

Sado Island is located off the Niigata City seashore and it is the second largest island in Japan after Okinawa Island. Sado Island is famous for its Toki (crested ibis, *Nipponia nippon*), which is an endangered species in Japan. The inhabitants of Sado city and its farmers are trying to make an ideal habitat for Toki. The feed for Toki are small fish and insects, such as the loach, grasshoppers, and worms as well as small river crabs, and frogs. The farmers are making an effort to keep the environment agriculturally sound to protect the ibis from

Sado city awards the farmers a harmonizing environment certificate known as the "homeland to live with crested ibis" if the farmers adopt an ibis‐friendly agricultural method. Farmers create a narrow pond, preserve bio‐diversity with winter‐flooding, and reduce the use of chemical fertilizers and agricultural chemicals by over 50% compared with conventional

However, the effects of this ibis‐friendly agricultural method, which also include abolish‐ ing drying paddy field after transplanting, does not equate to palatability of the rice grains. Therefore, the relationship between the palatability of rice and agronomical condition to pre‐ serve the bio‐diversity for ibis was investigated. Furthermore, the quality of rice grown in Sado Island was compared with that of rice grown in mountainous areas and in the field.

ing AAC of Chinese rice cultivars as unknown samples.

mountainous region and the field region in Sado Island, Japan.

factors.

104 Advances in International Rice Research

*5.2.1. Introduction*

extinction.

cultivation.

ated as the highest quality rice.

#### *<IP_ADDRESS>. Comparison of Sado Koshihikari and the other premium rice in Japan*

Ten premium rice cultivars, including "Koshihikari" from Sado Island, "Sagabiyori," "Yumepirika," "Akitakomachi," "Tsuyahime,""Hitomebore," and "Koshihikari from Sado" were subjected to physicochemical measurements and sensory test.

### *<IP_ADDRESS>. Comparison of mountainous and field regions*

Rice samples grown in eight regions, including the mountainous and field regions, were sub‐ jected to the physicochemical measurements to evaluate rice quality.

#### *<IP_ADDRESS>. Effects of the ibis‐friendly cultivations on the palatability of the rice grains*

Rice grains were harvested after an ordinary or ibis‐friendly cultivation and were subjected to quality evaluations. Ibis‐friendly cultivation meant that farmers adopted winter‐flooding (keeping water even during the winter season to save the habitat for Toki in winter) or dele‐ tion of "Nakaboshi" (drainage of paddy field for approximately a week after transplanting to activate the roots of rice plant).

#### *<IP_ADDRESS>. Preparation of polished rice samples*

After de‐husking, brown rice was polished to a milling yield of 90–91%, using an experimen‐ tal TM05 rice milling machine (Satake, Co. Ltd. Higashihiroshima, Japan). Rice flours were prepared by a cyclone mill (SFC‐S1, Udy, Fort Colins, CO, USA).

#### *<IP_ADDRESS>. Amylose content*

Amylose content was measured by the iodine colorimetric method. Calibration samples were prepared by mixing the standard potato amylose (Type III, Sigma Chemical Co., St. Louis, MO, USA) and standard amylopectin (waxy rice removed from fat and proteins).

#### *<IP_ADDRESS>. Measurements of protein content, Mido, and quality score*

Protein contents and quality scores were measured with a near‐infrared spectrometer (AN820, Kett Electric Laboratory Co. Ltd., Tokyo, Japan) (Near Infrared Spectrometer, Foss Japan Co. Ltd, Tokyo, Japan). Mido was measured using a Midometer (Toyorice, Wakayama, Japan).

#### *<IP_ADDRESS>. Measurement of the physical properties of the boiled rice grains*

Polished rice grains (10 g) were added with 16 mL of distilled water in an aluminum cup. The rice was in the water for 1 h, cooked for 25 min in the automatic electric rice cooker (SR‐ SW182, Panasonic Co. Ltd., Kadoma, Japan) and kept warm for 10 min in it. After the rice was kept warm, the boiled rice grains were moved into a plastic bag and kept in the bag for 2 h at 25°C. Thereafter, the physical property (hardness and stickiness) of each boiled rice grain (20 samples) was measured by a Tensipresser (My Boy System, Taketomodenki Co. Ltd., Tokyo, Japan), as reported by Okadome et al. (single grain low‐compression high‐com‐ pression test).

## **5.3. Results and discussion**

## *5.3.1. Comparison of palatability of premium rice cultivars in Japan*

"Koshihikari" from the Sado Island received extremely high value for the quality value, Mido value, and low value for protein. "Koshihikari" from Sado Island had an extremely low hardness in surface layer of boiled grains, whereas extremely low amylose rice such as "Yumepirika" had the lowest hardness in surface layer of boiled rice gains. The ratio of stickiness to hardness of surface layer of boiled grains was the highest for "Yumepirika" followed by "Koshihikari" from Sado Island. Palatability of the "Koshihikari" from Sado Island seems to be one of the best premium rice cultivars in Japan due to its low protein content.

## *5.3.2. Comparison of mountainous and field regions*

As a result of measurement of physical properties, five rice samples from mountainous regions showed a lower pasting temperature and a higher ratio of adhesiveness to hardness (A6/A4, overall). It was reported that the ratio of adhesiveness to hardness is correlated with palatability of boiled rice grains. Rice samples grown in the mountainous region seems to be more palatable than those in the field region because the former rice is more adhesive.

#### *5.3.3. Effect of winter‐flooding and Nakaboshi on palatability of rice*

Rice samples grown using winter‐flooding (without "Nakaboshi") showed higher amylose contents, than those grown with winter‐flooding and "Nakaboshi." Rice grains grown using winter‐flooding and Nakaboshi had lower amylose contents implying that the boiled rice grains of this group were softer and stickier than the rice grains subjected to winter‐flooding alone. In case of cultivation using winter‐flooding, the rice grains grown using "Nakaboshi" became stickier after boiling compared with those cultivated without "Nakaboshi." In case of cultivation without Nakaboshi, rice samples grown using winter‐flooding became less adhesive after boiling compared with those grown without winter‐flooding. These results are shown in **Figure 7**.

To summarize, farmers should adopt Nakaboshi in case of winter‐flooding, and avoid win‐ ter‐flooding in case of not performing Nakaboshi. Although adoption of winter‐flooding and not performing Nakaboshi are recommended to maintain biodiversity, simultaneously per‐ forming of both of these measures negatively affects the palatability of the boiled rice grains.

#### **5.4. Conclusions**

Farmers in Sado city make an effort to harmonize the environment with sound agriculture to protect the ibis from extinction. The palatability of "Koshhikari" from Sado Island is among

**Figure 7.** The effect of winter‐flooding and Nakaboshi on amylose contents of rice grains.

the premium rice cultivars in Japan. The rice quality from Sado Island grown in mountainous areas and those in field regions were examined along with the palatability of rice and the agro‐ nomical conditions to preserve the bio‐diversity for the ibis.

The results show that the palatability of "Koshihikari" from Sado Island seems to be one of the best among the premium rice cultivars in Japan because of its low protein contents. Five rice samples from mountainous regions showed better physical properties compared with three rice samples grown in the fields. Adoption of both winter‐flooding and not per‐ forming Nakaboshi is recommended to maintain biodiversity; however, simultaneously performing both of these measures negatively affects the palatability of the boiled rice grains.

## **6. Summary**

grain (20 samples) was measured by a Tensipresser (My Boy System, Taketomodenki Co. Ltd., Tokyo, Japan), as reported by Okadome et al. (single grain low‐compression high‐com‐

"Koshihikari" from the Sado Island received extremely high value for the quality value, Mido value, and low value for protein. "Koshihikari" from Sado Island had an extremely low hardness in surface layer of boiled grains, whereas extremely low amylose rice such as "Yumepirika" had the lowest hardness in surface layer of boiled rice gains. The ratio of stickiness to hardness of surface layer of boiled grains was the highest for "Yumepirika" followed by "Koshihikari" from Sado Island. Palatability of the "Koshihikari" from Sado Island seems to be one of the best premium rice cultivars in Japan due to its low protein

As a result of measurement of physical properties, five rice samples from mountainous regions showed a lower pasting temperature and a higher ratio of adhesiveness to hardness (A6/A4, overall). It was reported that the ratio of adhesiveness to hardness is correlated with palatability of boiled rice grains. Rice samples grown in the mountainous region seems to be

Rice samples grown using winter‐flooding (without "Nakaboshi") showed higher amylose contents, than those grown with winter‐flooding and "Nakaboshi." Rice grains grown using winter‐flooding and Nakaboshi had lower amylose contents implying that the boiled rice grains of this group were softer and stickier than the rice grains subjected to winter‐flooding alone. In case of cultivation using winter‐flooding, the rice grains grown using "Nakaboshi" became stickier after boiling compared with those cultivated without "Nakaboshi." In case of cultivation without Nakaboshi, rice samples grown using winter‐flooding became less adhesive after boiling compared with those grown without winter‐flooding. These results are

To summarize, farmers should adopt Nakaboshi in case of winter‐flooding, and avoid win‐ ter‐flooding in case of not performing Nakaboshi. Although adoption of winter‐flooding and not performing Nakaboshi are recommended to maintain biodiversity, simultaneously per‐ forming of both of these measures negatively affects the palatability of the boiled rice grains.

Farmers in Sado city make an effort to harmonize the environment with sound agriculture to protect the ibis from extinction. The palatability of "Koshhikari" from Sado Island is among

more palatable than those in the field region because the former rice is more adhesive.

pression test).

content.

shown in **Figure 7**.

**5.4. Conclusions**

**5.3. Results and discussion**

106 Advances in International Rice Research

*5.3.1. Comparison of palatability of premium rice cultivars in Japan*

*5.3.3. Effect of winter‐flooding and Nakaboshi on palatability of rice*

*5.3.2. Comparison of mountainous and field regions*

There are various kinds of rice cultivars of which qualities are diversified, such as hard Indica rice and soft Japonica rice in the world. Consumers in southern Asia prefer hard rice grains and people in North‐eastern Asia like soft and sticky rice grains. Novel method to evaluate the quality of the cooked rice is necessary to breed high‐quality rice cultivars and to select the suitable rice for each consumer and for each purpose. We try to develop the novel method to evaluate the rice quality using various kinds of apparatus, such as Tensipresser, RVA, NIR, and spectrophotometer. Simple, rapid, and accurate method to evaluate the quality of rice grains is very valuable.

## **Author details**

Ken'ichi Ohtsubo\* and Sumiko Nakamura

\*Address all correspondence to<EMAIL_ADDRESS>
Niigata University of Pharmacy and Applied Life Sciences, Niigata City, Japan

## **References**

[10] Shimizu N, Katsura J,Yanagisawa T, Inoue S, Withey RP, Cowe IA, Eddison CG, Withey RP, Blakeney A, Kimura T, Yoshizaki S, Okadome H, Toyoshima H, Ohtsubo K: Determination of apparent amylose content in Japanese milled rice using near‐infrared transmission spectroscopy. Food Sci. Technol. Res. 1999;5:337–342.

and spectrophotometer. Simple, rapid, and accurate method to evaluate the quality of rice

[1] Ohtsubo K, Toyoshima H, Okadome H: Quality assay of rice using traditional and novel

[2] Juliano BO: A simplified assay for milled rice amylose. Cereal Sci. Today. 1971;16:334–340,

[3] Toyoshima H, Okadome H, Ohtsubo K, Suto M, Horisue N, Inatsu O, Narizuka A, Aizaki M, Inouchi N, Fuwa H: Cooperative test on the small‐scale rapid method for the gelatinization properties test of rice flours with a rapid visco analyser (in Japanese).

[4] Ohtsubo K, Ishima T, Yanase H: Colorimetric method for fat acidity measurement of rice

[5] Batcher OM, Deary PA, Dawson EH: Cooking quality of 26 variety of milled white rice.

[6] Okadome H, Toyoshima H, Ohtsubo K: Multiple measurements of physical prop‐ erties of individual cooked rice grains with a single apparatus. Cereal Chem.

[7] Chikubu S, Watanabe S, Sugimoto T, Manabe M, Sakai F, Taniguchi Y: Establishment of palatability estimation formula of rice by multiple regression analysis (in Japanese).

[8] Iwamoto M, Suzuki T, Kongseree N, Uozumi J, Inatsu O: Analysis of protein and amino acid contents in rice flour by near‐infrared spectroscopy (in Japanese). Nippon Shokuhin

[9] Inatsu O: Studies on improving the eating quality of Hokkaido rice (in Japanese). Rep.

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Ken'ichi Ohtsubo\* and Sumiko Nakamura

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Niigata University of Pharmacy and Applied Life Sciences, Niigata City, Japan

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## **Comparison on Grain Quality Between Super Hybrid and Popular Inbred Rice Cultivars Under Two Nitrogen Management Practices Comparison on Grain Quality Between Super Hybrid and Popular Inbred Rice Cultivars Under Two Nitrogen Management Practices**

Min Huang, Shuanglü Shan, Jiana Chen, Min Huang, Shuanglü Shan, Jiana Chen, Fangbo Cao, Ligeng Jiang and Yingbin Zou

Fangbo Cao, Ligeng Jiang and Yingbin Zou

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/66386

#### **Abstract**

[24] Asaoka M, Okuno K: Effect of environmental temperature at the milky stage on amylose content and fine structure of amylopectin of waxy and nonwaxy endosperm starches of

[25] Inouchi N, Ando H, Asaoka M, Okuno K, Fuwa H: The effect of environmental tempera‐ ture on distribution of unit chains of rice amylopectin. Starch/Strake. 2000;52:8–12. [26] Adam A, Karen AKM, Anna MM, Donn HB, Brucc RH: Effect of growth location in the United States on amylose content, amylopectin fine structure, and thermal properties of

[27] Umemoto T, Nakamura Y, Satoh H, Terashima K: Differences in amylopectin structure between two rice varieties in relation to the effects of temperature during grain‐filling.

[28] Takami K, Koriyama T, Ohtsubo K: Staling characteristics of cooked low‐amylose rice and a proposal of evaluation method. Nippon Shokuhin Kagaku Kogaku Kaishi.

[29] Mitsukawa N, Konishi R, Uchiki M, Masumura T, Tanaka K: Molecular cloning and characterization of a cystein‐rich 16.6 kDa prolamin in rice seeds. Biosci. Biotechnol.

[30] Honjyo K: Variation of protein content between rice varieties and the influences of envi‐

[31] Matsui T, Ishizaki K, Nakamura S, Ohtsubo K: Differences in physical properties of boiled rice and gelatinization properties of rice flour between pairs of near‐isogenic lines for low glutelin gene (Lgc1) locus. Nippon Shokuhin Kagaku Kogaku kaishi. 2013;60:

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110 Advances in International Rice Research

204–211.

This study was conducted to determine the differences in grain quality traits between super hybrid and popular inbred rice cultivars grown under two nitrogen (N) management practices. Field experiments were done at the Experimental Farm of Guangxi University, Guangxi Province, China in early and late rice-growing seasons in 2014. Two representative super hybrid cultivars Liangyoupeijiu (LYPJ) and Y-liangyou 1 (YLY1) and a popular inbred rice cultivar Huanghuazhan (HHZ) were grown under fixed-time N management (FTNM) and site-specific N management (SSNM) practices in each season. Grain quality traits and N uptake were measured for each cultivar. LYPJ and YLY1 had higher milling efficiency, poorer appearance and palatability, and equal nutritional value than HHZ. The higher milling efficiency and poorer appearance in LYPJ and YLY1 were associated with their higher rice width compared with HHZ. Total N application rate was reduced by 15–20% under SSNM than under FTNM, whereas there was nearly no significant difference in grain quality between SSNM and FTNM. Our results suggest that (1) strategies for grain quality improvement in super hybrid rice should be focused on appearance and palatability, and (2) replacing FTNM with SSNM can reduce N input without sacrificing grain quality in rice production.

**Keywords:** grain quality, grain shape, nitrogen management, super hybrid rice, temperature

and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution

## **1. Introduction**

Rice is the staple food for about 65% of the population of China and therefore rice productivity is critical to the national food security [1]. Although Chinese rice production has increased more than threefold in the past five decades [2], rapid population growth and economic development have been posing a growing pressure for increased food production [3]. It is projected that China will need to produce about 20% more rice by 2030 in order to fulfil its domestic needs [4]. To achieve this goal, great efforts should be made to breed new rice cultivars with higher yield potential [5]. In 1996, China established a nationwide mega-project on the development of super rice based on the ideotype concept [6]. In 1998, Prof. Longping Yuan proposed a strategy for developing super hybrid rice by combining an ideotype approach with the use of inter-subspecific heterosis [7]. The main target of super hybrid rice breeding is to develop high-yielding cultivars. However, the demand for high quality rice increases in China as living standards improve [8]. In 2000, 40% of the rice area was planted with rice cultivars with high grain quality and most of these cultivars were inbreds [9]. Hence, whether the super hybrid rice cultivars can be widely planted in China to some extent depends on their grain quality.

In rice, grain quality is generally classified into four components: milling efficiency, appearance, cooking and eating characteristics and nutritional value [10]. Milling efficiency is typically assessed as brown rice percentage (BRP), milled rice percentage (MRP) and head rice percentage (HRP) [11]. Appearance is often judged by the percentage of chalky rice grains (PCRG) and degree of chalkiness (DC) [12]. Cooking and eating characteristics are mostly determined by gelatinization temperature (GT), amylose content (AC) and gel consistency (GC) of the grain endosperm [13]. A nutritional value is commonly evaluated by protein content (PC) [14]. Among these, milling and appearance traits are highly correlated with grain shape. In general, rice length (RL), rice length-to-width ratio (RLWR), or length-to-thickness ratio are negatively associated with grain milling efficiency, while increased rice width (RW) and thickness tend to result in increased milling efficiency [15] but poorer appearance [16, 17]. In addition, there are strong relationships between some of the grain quality traits. Chalkiness reduces grain resistance to forces applied during the milling process, causing a decrease in HRP [18, 19]. Brown rice with high PC is more resistant to abrasive milling than that with low PC [20].

Rice grain quality depends not only on cultivars but also on crop management practices and environmental conditions [21, 22]. N application has been reported as a common management practice that affects rice grain quality. Leesawatwong et al. [20] observed that the N application increased the milling efficiency and nutritional value in four Thai extra-long grain rice cultivars. Ning et al. [23] found that contents of four proteins (albumin, globulin, prolamin and gutelin) were increased with the increased N level in 31 japonica cultivars. Similarly, Wang et al. [24] reported that PC increased with an increase in N rates in two hybrid rice cultivars and there was a significantly positive relationship between PC and the total N uptake (TNU) for each cultivar. The temperature, especially daily mean temperature during grain-filling period, is one of the dominant climatic factors affecting rice grain quality [25]. High temperature may significantly accelerate the grain-filling rate, but correspondingly shorten its duration, thus resulting in loosely packed starch granules, decreased grain weight and HRP and increased PCRG.

Recently, there has been a report describing the grain quality of a super hybrid rice cultivar Liangyoupeijiu (LYPJ) grown under different N rates [24]. Their results showed that LYPJ had higher HRP, AC and GC but lower PCRG and PC than an ordinary hybrid rice cultivar, Shanyou 63, across a wide range of N rates. However, this study was conducted using only one super hybrid cultivar in comparison with a check cultivar. Furthermore, although rice breeders in China often use Shanyou 63 as a check cultivar because of its superior yield stability, its grain quality is not good enough to suit the preference of consumers. Therefore, it is difficult to conclude whether the grain quality of super hybrid rice is good or not. In our current study, we compared two super hybrid rice cultivars with a popular inbred rice cultivar with good quality under two N management practices in two seasons. The objectives of this study were to (1) determine the differences in grain quality traits between super hybrid and popular inbred rice cultivars and (2) the effects of N management practices on rice grain quality.

## **2. Materials and methods**

## **2.1. Site and soil**

**1. Introduction**

112 Advances in International Rice Research

Rice is the staple food for about 65% of the population of China and therefore rice productivity is critical to the national food security [1]. Although Chinese rice production has increased more than threefold in the past five decades [2], rapid population growth and economic development have been posing a growing pressure for increased food production [3]. It is projected that China will need to produce about 20% more rice by 2030 in order to fulfil its domestic needs [4]. To achieve this goal, great efforts should be made to breed new rice cultivars with higher yield potential [5]. In 1996, China established a nationwide mega-project on the development of super rice based on the ideotype concept [6]. In 1998, Prof. Longping Yuan proposed a strategy for developing super hybrid rice by combining an ideotype approach with the use of inter-subspecific heterosis [7]. The main target of super hybrid rice breeding is to develop high-yielding cultivars. However, the demand for high quality rice increases in China as living standards improve [8]. In 2000, 40% of the rice area was planted with rice cultivars with high grain quality and most of these cultivars were inbreds [9]. Hence, whether the super hybrid rice cultivars can be widely planted in China to some extent depends on their grain quality.

In rice, grain quality is generally classified into four components: milling efficiency, appearance, cooking and eating characteristics and nutritional value [10]. Milling efficiency is typically assessed as brown rice percentage (BRP), milled rice percentage (MRP) and head rice percentage (HRP) [11]. Appearance is often judged by the percentage of chalky rice grains (PCRG) and degree of chalkiness (DC) [12]. Cooking and eating characteristics are mostly determined by gelatinization temperature (GT), amylose content (AC) and gel consistency (GC) of the grain endosperm [13]. A nutritional value is commonly evaluated by protein content (PC) [14]. Among these, milling and appearance traits are highly correlated with grain shape. In general, rice length (RL), rice length-to-width ratio (RLWR), or length-to-thickness ratio are negatively associated with grain milling efficiency, while increased rice width (RW) and thickness tend to result in increased milling efficiency [15] but poorer appearance [16, 17]. In addition, there are strong relationships between some of the grain quality traits. Chalkiness reduces grain resistance to forces applied during the milling process, causing a decrease in HRP [18, 19]. Brown rice with high PC is more resistant to abrasive milling than that with low PC [20].

Rice grain quality depends not only on cultivars but also on crop management practices and environmental conditions [21, 22]. N application has been reported as a common management practice that affects rice grain quality. Leesawatwong et al. [20] observed that the N application increased the milling efficiency and nutritional value in four Thai extra-long grain rice cultivars. Ning et al. [23] found that contents of four proteins (albumin, globulin, prolamin and gutelin) were increased with the increased N level in 31 japonica cultivars. Similarly, Wang et al. [24] reported that PC increased with an increase in N rates in two hybrid rice cultivars and there was a significantly positive relationship between PC and the total N uptake (TNU) for each cultivar. The temperature, especially daily mean temperature during grain-filling period, is one of the dominant climatic factors affecting rice grain quality [25]. High temperature may significantly accelerate the grain-filling rate, but correspondingly shorten its duration, thus resulting in loosely packed starch granules, decreased grain weight and HRP and increased PCRG.

Field experiments were conducted at the Experimental Farm of Guangxi University (22°51′ N, 108°17′ E, 78 m a.s.l.), Guangxi Province, China in early and late rice-growing seasons in 2014. The soil of the experimental field was an Ultisol (USDA taxonomy) with the following properties: pH 6.75, 32.3 g kg–1 organic matter, 120 mg kg–1 alkali-hydrolysable N, 31.6 mg kg–1 available P and 126 mg kg–1 available K. The soil test was based on samples taken from the 0 to 20 cm soil layer.

**Table 1.** Information about rice cultivars used in the study.

#### **2.2. Plant and treatments**

Three rice cultivars, including Liangyoupeijiu (LYPJ), Y-liangyou 1 (YLY1) and Huanghuazhan (HHZ), were used in this study. LYPJ and YLY1 are two representatives of high-yielding cultivars developed from China's super hybrid rice breeding project [26]. HHZ has been widely grown by rice farmers in southern China because of its good grain quality. Detailed information about rice cultivars is given in **Table 1**.  A

a Basal was defined as 1 day before transplanting, early tillering as 7 days after transplanting, panicle initiation as the first appearance of differentiated apex and spikelet differentiation as the appearance of glumous flower primordia at the tips of elongating primary rachis-branches [27].

b A chlorophyll meter (SPAD-502, Soil-Plant Analysis Development Section, Minolta Camera Co., Osaka, Japan) was used to determine top dressings. SPAD value was measured on 10 topmost fully expanded leaves per plot. At panicle initiation, if SPAD < 37, apply 60 kg ha–1; if between 37 and 39, apply 45 kg ha–1; if > 39, apply 30 kg ha–1. At spikelet differentiation, if SPAD < 37, apply 45 kg ha–1; if between 37 and 39, apply 30 kg ha–1; if between 39 and 42, apply 15 kg ha–1; if > 42, apply 0 kg ha–1 [28].

**Table 2.** N application timing and rate and the total N application rate for fixed-time N management (FTNM) and sitespecific N management (SSNM) in early and late seasons.

split-plot design was used with N management practices as main plots and cultivars as subplots. The experiment was replicated three times and subplot size was 20 m2 .

Pre-germinated seeds were sown in a seedbed. Twenty-two-day-old seedlings were transplanted on 12 April and 31 July in early and late seasons, respectively. Transplanting was carried out at a hill spacing of 20 cm × 27 cm with two seedlings per hill. In addition to the N fertilizer, plants received 112.5 kg P2 O5 ha–1 and 157.5 kg K2 O ha–1. P fertilizer was applied at basal. K fertilizer was split equally at basal and panicle initiation. The regimen for water management was in the sequence of flooding, midseason drainage, re-flooding and moist intermittent irrigation. Pests and weeds were controlled using chemicals.

#### **2.3. Sampling and measurements**

Ten hills were sampled diagonally from a 5 m2 harvest area (excluding plants in the borders) for each replication at maturity. These samples were separated into straw and panicles. Panicles were threshed by hand and the filled grains were separated from unfilled grains by submerging them in tap water. Dry weights of straw, rachis and filled and unfilled grains were determined after oven drying at 70°C to constant weight. The N content of straw, rachis and filled and unfilled grains were determined by an autoanalyzer (Integral Futura, Alliance Instruments, Frépillon, France) to calculate N uptake in filled grains (NUFG) and the total N uptake (TNU). Plants were harvested from the 5 m2 area and grains were threshed and sundried. Filled grains were separated from unfilled grains and debris by winnowing. Around 500 g of the filled grains were taken from each sample and stored at room temperature for 4 months to ensure stable grain quality [29]. A weight of 130 g of the stored grains was dehulled with a roller sheller and polished in a polishing machine according to the National Standard NT 147-88 of China. Brown rice percentage (BRP), milled rice percentage (MRP) and head rice percentage (HRP) were calculated based on the rough rice weight. Percentages of chalky rice grains (PCRG), degree of chalkiness (DC), gelatinization temperature (GT), gel consistency (GC), amylose content (AC) and protein content (PC) were determined according to the descriptions of Huang et al. [30]. Rice length (RL), rice width (RW) and rice length-towidth ratio (RLWR) were measured on 10 head rice grains using a photoenlarger magnified at 10×. Temperature data were collected from the local weather station.

## **2.4. Statistical analysis**

Data were analyzed following analysis of variance (Statistix 8, Analytical software, Tallahassee, FL, USA). The statistical model used included sources of variation due to replication, cultivar, N management practice, season and interactions of cultivar × N management practice, cultivar × season, N management practice × season and cultivar × N management practice × season. Means of cultivars were compared based on the least significant difference (LSD) test at the 0.05 probability level.

## **3. Results**

split-plot design was used with N management practices as main plots and cultivars as sub-

**Table 2.** N application timing and rate and the total N application rate for fixed-time N management (FTNM) and site-

**Season N application timing and rate (kg ha–1)a Total N**

Late 56 60 60 15 191

 Basal was defined as 1 day before transplanting, early tillering as 7 days after transplanting, panicle initiation as the first appearance of differentiated apex and spikelet differentiation as the appearance of glumous flower primordia at the

 A chlorophyll meter (SPAD-502, Soil-Plant Analysis Development Section, Minolta Camera Co., Osaka, Japan) was used to determine top dressings. SPAD value was measured on 10 topmost fully expanded leaves per plot. At panicle initiation, if SPAD < 37, apply 60 kg ha–1; if between 37 and 39, apply 45 kg ha–1; if > 39, apply 30 kg ha–1. At spikelet differentiation, if SPAD < 37, apply 45 kg ha–1; if between 37 and 39, apply 30 kg ha–1; if between 39 and 42, apply 15 kg

**initiation**

**Spikelet differentiation**

**Basal Early tillering Panicle**

FTNM Early and late 112.5 45 45 22.5 225 SSNMb Early 56 60 45 15 176

Pre-germinated seeds were sown in a seedbed. Twenty-two-day-old seedlings were transplanted on 12 April and 31 July in early and late seasons, respectively. Transplanting was carried out at a hill spacing of 20 cm × 27 cm with two seedlings per hill. In addition to the

at basal. K fertilizer was split equally at basal and panicle initiation. The regimen for water management was in the sequence of flooding, midseason drainage, re-flooding and moist

ders) for each replication at maturity. These samples were separated into straw and panicles. Panicles were threshed by hand and the filled grains were separated from unfilled grains by submerging them in tap water. Dry weights of straw, rachis and filled and unfilled grains were determined after oven drying at 70°C to constant weight. The N content of straw, rachis and filled and unfilled grains were determined by an autoanalyzer (Integral Futura, Alliance Instruments, Frépillon, France) to calculate N uptake in filled grains (NUFG) and the total N

dried. Filled grains were separated from unfilled grains and debris by winnowing. Around 500 g of the filled grains were taken from each sample and stored at room temperature for 4 months to ensure stable grain quality [29]. A weight of 130 g of the stored grains was dehulled with a roller sheller and polished in a polishing machine according to the National Standard NT 147-88 of China. Brown rice percentage (BRP), milled rice percentage (MRP) and head rice percentage (HRP) were calculated based on the rough rice weight. Percentages

ha–1 and 157.5 kg K2

.

**application rate (kg ha–1)**

O ha–1. P fertilizer was applied

harvest area (excluding plants in the bor-

area and grains were threshed and sun-

plots. The experiment was replicated three times and subplot size was 20 m2

O5

intermittent irrigation. Pests and weeds were controlled using chemicals.

N fertilizer, plants received 112.5 kg P2

tips of elongating primary rachis-branches [27].

specific N management (SSNM) in early and late seasons.

ha–1; if > 42, apply 0 kg ha–1 [28].

**N management practice**

114 Advances in International Rice Research

a

b

**2.3. Sampling and measurements**

Ten hills were sampled diagonally from a 5 m2

uptake (TNU). Plants were harvested from the 5 m2

Daily mean temperature trended to increase during the early season period, whereas a decrease trend was observed during the late season period (**Figure 1a**). Average daily mean temperatures during the grain-filling period were 28.6°C for HHZ and 29.2°C for LYPJ and YLY1 in early season (**Figure 1b**), as well as 24.0°C for HHZ and 23.3°C for LYPJ and YLY1 in the season (**Figure 1c**).

Significant cultivar effects were observed for all measured grain quality traits except for PC (**Tables 3** and **4**). LYPJ had slightly higher BRP and MRP than HHZ, while the differences were not significant between YLY1 and HHZ. MRP was higher in LYPJ and YLY1 than in HHZ by 13 and 30%, respectively. LYPJ and YLY1 showed 14- and 9-fold, respectively, higher PCRG than HHZ. DC was 20-fold higher in LYPJ and 11-fold higher in YLY1 compared with HHZ. LYPJ showed 12% lower GT than HHZ, while the difference between YLY1 and HHZ was relatively small. AC was 29% higher in LYPJ but 12% lower in YLY1 than in HHZ. GC was 8% higher in LYPJ, but 13% lower in YLY1 than in HHZ. N management practice had no significant effects on any of the grain quality traits except for GT. SSNM showed slightly higher GT than FTNM. Seasonal effects were significant on all the grain quality traits except for BRP. Compared to early season, late season had lower MRP, PCRG, DC and GC but higher HRP, GT, AC and PC. The interactive effects between cultivar and season were significant on all the grain quality traits except for PC, while the other interactive effects were generally insignificant.

There were significant cultivar effects on all three grain shape traits (**Tables 3** and **4**). RL was slightly lower in LYPJ than in YLY1 and HHZ. LYPJ and YLY1 had 12 and 11%, respectively, higher RW than HHZ. RLWR was lower in LYPJ and YLY1 than in HHZ by 13 and 10%, respectively. N management practice showed no significant effects on RL and RLWR, whereas SSNM had a slightly but significantly higher RW than FTNM. A significant seasonal effect was observed for RL but not for either RW or RLWR. RL was slightly lower in early season than in late season.

Cultivar and N management practice had no significant effects on TNU and NUFG (**Figure 2a** and **b**). Significant seasonal effects were observed for TNU and NUFG. Late season showed higher TNU and NUFG than early season by 5 and 22%, respectively.

**Figure 1.** Daily mean temperature during early and late rice-growing seasons (a) and grain-filling period (from heading to maturity) in the early (b) and late (c) seasons. In (a), horizontal lines denote the duration (from sowing to harvesting) of early and late seasons and vertical lines represent the heading dates for three rice cultivars (HHZ, Huanghuazhan; LYPJ, Liangyoupeijiu; and YLY1, Y-liangyou 1).

#### **4. Discussion**

Our results indicate that the super hybrid rice cultivars LYPJ and YLY1 had higher milling efficiency, poorer appearance and equal nutritional value compared with the popular inbred rice cultivar HHZ. Wang et al. [24] also observed a higher milling efficiency in LYPJ than in an ordinary hybrid rice cultivar Shanyou 63 and they pointed out that the higher milling efficiency in LYPJ was associated its lower PCRG compared with Shanyou 63. In this regard, it is suggested that chalkiness reduces grain resistance to forces applied during the milling process, causing a decrease in milling efficiency [18, 19]. However, this is not the case in the present study, in which LYPJ and YLY1 had higher PCRG and DC than HHZ. In fact, in addition to the chalkiness, grain shape and PC are also correlated with grain milling efficiency in

Cultivar and N management practice had no significant effects on TNU and NUFG (**Figure 2a** and **b**). Significant seasonal effects were observed for TNU and NUFG. Late season showed

Our results indicate that the super hybrid rice cultivars LYPJ and YLY1 had higher milling efficiency, poorer appearance and equal nutritional value compared with the popular inbred rice cultivar HHZ. Wang et al. [24] also observed a higher milling efficiency in LYPJ than in an ordinary hybrid rice cultivar Shanyou 63 and they pointed out that the higher milling efficiency in LYPJ was associated its lower PCRG compared with Shanyou 63. In this regard, it is suggested that chalkiness reduces grain resistance to forces applied during the milling process, causing a decrease in milling efficiency [18, 19]. However, this is not the case in the present study, in which LYPJ and YLY1 had higher PCRG and DC than HHZ. In fact, in addition to the chalkiness, grain shape and PC are also correlated with grain milling efficiency in

**Figure 1.** Daily mean temperature during early and late rice-growing seasons (a) and grain-filling period (from heading to maturity) in the early (b) and late (c) seasons. In (a), horizontal lines denote the duration (from sowing to harvesting) of early and late seasons and vertical lines represent the heading dates for three rice cultivars (HHZ, Huanghuazhan;

higher TNU and NUFG than early season by 5 and 22%, respectively.

116 Advances in International Rice Research

**4. Discussion**

LYPJ, Liangyoupeijiu; and YLY1, Y-liangyou 1).

**Table 3.** F values of analysis of variance for effects of cultivar, N management practice and season on grain quality and shape traits in rice.

\*\* Significance at the 0.01 probability level.

ns Non-significance at the 0.05 probability level.

**Table 4.** Grain quality and shape traits in three rice cultivars, including two super hybrid cultivars Liangyoupeijiu (LYPJ) and Y-liangyou 1 (YLY1) and a popular inbred cultivar Huanghuazhan (HHZ), grown under fixed-time N management (FTNM) and site-specific N management (SSNM) in early and late seasons. Comparison on Grain Quality Between Super Hybrid and Popular Inbred Rice Cultivars Under... http://dx.doi.org/10.5772/66386 119

**Figure 2.** Total N uptake (TNU) and N uptake in filled grains (NUFG) in three rice cultivars, including two super hybrid cultivars Liangyoupeijiu (LYPJ) and Y-liangyou 1 (YLY1) and a popular inbred cultivar Huanghuazhan (HHZ), grown under fixed-time N management (FTNM) and site-specific N management (SSNM). Vertical bars represent SE (*n* = 3). \* Significance at the 0.05 probability level. \*\*Significance at the 0.01 probability level. nsNon-significance at the 0.05 probability level.

rice [15, 20]. Generally, increased RW or PC tends to result in increased milling efficiency. In this study, the former seems to be responsible for the higher milling efficiency in LYPJ and

**Season**

**practice**

Early

 FTNM

LYPJ

YLY1

HHZ

SSNM

LYPJ

YLY1

HHZ

LYPJ

YLY1

HHZ

SSNM

LYPJ

YLY1

HHZ

Mean of

cultivar

LYPJ

YLY1

HHZ

 80.2b

 80.3b

 81.0a

72.1a

71.3b

71.2b

 48.4c temperature; AC, amylose content; GC, gel consistency; PC, protein content.

b RL, rice length; RW, rice width; RLWR, rice length-to-width ratio.

c Values in parenthesis are SE (*n* = 3).

 2.4c

 0.25c

 6.93a Note: Means of cultivars with the same letters for each parameter are not significantly different according to LSD at the 0.05 probability level.

a BRP, brown rice percentage; MRP, milled rice percentage; HRP, head rice percentage; PCRG, percentage of chalky rice grains; DC, degree of chalkiness; GT, gelatinization

**Table 4.** Grain quality and shape traits in three rice cultivars, including two super hybrid cultivars Liangyoupeijiu (LYPJ) and Y-liangyou 1 (YLY1) and a popular inbred

cultivar Huanghuazhan (HHZ), grown under fixed-time N management (FTNM) and site-specific N management (SSNM) in early and late seasons.

 18.1b

 79.5b

 9.6ab

 6.75a

 2.00c

 3.38a

 63.0a

 20.7b

 2.63b

 6.81b

 16.0c

 69.5c

 9.8a

 6.73a

 2.21b

 3.03b

 54.8b

 34.0a

 5.08a

 6.09c

 23.3a

 86.1a

 9.4b

 6.62b

 2.25a

 2.94c

 79.9(0.6) 70.6(0.4) 57.0(1.7)

 2.0(0.6)

 0.30(0.06)

 7.00(0.05) 18.8(0.2)

 77.7(1.9)

 10.2(0.3)

 6.73(0.07)

 2.00(0.02)

 3.37(0.10)

 80.8(0.3) 71.6(0.3) 63.1(1.0) 23.7(0.9)

 80.5(0.1) 71.4(0.2) 56.6(1.2)

 79.5(0.8) 70.9(0.6) 54.5(4.9)

 2.3(0.7)

 20.7(5.0)

 2.37(0.50)

 2.57(0.38)

 6.90(0.10) 17.2(0.3)

 65.0(0.6)

 10.4(0.1)

 6.83(0.07)

 2.25(0.03)

 3.04(0.11)

 6.47(0.09) 23.4(0.2)

 88.3(0.3)

 10.3(0.4)

 6.67(0.03)

 2.30(0.02)

 2.90(0.14)

 0.23(0.09)

 6.93(0.07) 18.4(0.2)

 75.0(3.6)

 10.9(0.6)

 6.67(0.07)

 2.00(0.02)

 3.34(0.37)

 80.5(0.4) 71.5(0.6) 60.7(1.0) 23.3(4.4)

 80.4(0.4) 71.1(0.4) 60.0(0.7) 22.7(5.9)

Late

 FTNM

 80.8(0.5) 71.5(0.4) 40.0(1.7)

 2.0(0.4)

 0.13(0.04)

 2.43(0.69)

 2.27(0.44)

 7.00(0.05) 16.9(0.2)

 66.0(2.7)

 10.6(0.3)

 6.80(0.04)

 2.19(0.02)

 3.11(0.43)

 6.37(0.09) 23.0(0.2)

 84.7(1.8)

 10.5(0.3)

 6.63(0.04)

 2.21(0.02)

 3.00(0.48)

 6.83(0.05) 17.7(0.4)

 81.7(1.5)

 8.9(0.1)

 6.80(0.04)

 2.00(0.02)

 3.40(0.65)

 79.6(0.5) 70.8(0.6) 63.7(0.2) 14.7(4.1)

 81.0(0.2) 72.8(0.2) 50.6(1.0)

 80.5(0.2) 71.8(0.3) 42.2(2.0)

 3.3(0.7)

 42.7(2.2)

 7.07(0.27)

 2.13(0.48)

 6.73(0.07) 14.9(0.2)

 76.0(0.2)

 9.1(0.2)

 6.60(0.02)

 2.20(0.02)

 3.00(0.10)

 6.10(0.17) 23.4(0.2)

 86.0(2.0)

 8.6(0.1)

 6.60(0.03)

 2.25(0.03)

 2.93(0.17)

 0.33(0.07)

 6.93(0.04) 17.5(0.2)

 83.7(2.0)

 8.3(0.1)

 6.80(0.04)

 2.00(0.02)

 3.40(0.34)

 80.2(0.3) 71.3(0.6) 64.6(0.7) 21.0(2.1)

 82.1(0.4)c 73.1(0.4) 51.9(1.7)

**N management**

**Cultivar**

**BRP**

**MRP**

**HRP**

**PCRG**

**DC**

**GT**

 **AC**

**GC (mm)**

 **PC**

**RL (mm)**

 **RW (mm)**

 **RLWR**

**(%)**

**(%)**

**(%)**

**(%)**

**(%)**

**(%)**

 50.0(3.2)

 8.43(0.81)

 3.53(0.77)

 6.60(0.05) 14.8(0.2)

 71.0(1.0)

 8.9(0.2)

 6.67(0.03)

 2.22(0.01)

 3.00(0.14)

 5.43(0.07) 23.2(0.2)

 85.3(1.3)

 8.1(0.2)

 6.57(0.05)

 2.24(0.04)

 2.93(0.19)

118 Advances in International Rice Research

**(%)**

**Grain quality traita**

**Grain shape traitb**

YLY1 than in HHZ, because LYPJ and YLY1 had equal PC compared with HHZ. Moreover, it has been reported that there are positive relationships between RW with PCRG and DC [16, 17]. Therefore, the poorer appearance (higher PCRG and DC) in LYPJ and YLY1 might also be associated with their higher RW. These results also reveal that it may be difficult to achieve a synchronous improvement in milling efficiency and appearance in super hybrid rice. Among the cooking and eating quality traits, GT is often considered as an indicator affecting the cooking time of rice, for rice with higher GT requires a longer time to cook [31]. This point, however, is uncertain. Bhattacharya and Sowbhagya [32] observed that water uptake and hence the cooking time was strongly influenced by the surface area per unit weight. Other workers have also observed that water uptake of rice at boiling temperature is not related to GT but it is related to grain size and shape [33, 34]. In the present study, significant differences were observed both in GT and in grain shape between LYPJ and YLY1 with HHZ, suggesting that further studies are required to understand the difference in cooking characteristics between them. AC and GC have been considered the key indicators relating to palatability [31, 35]. Generally, consumers, especially in China, favor the rice with moderate AC and GC [25]. HHZ is such a cultivar. In the present study, LYPJ and YLY1 had largely higher or lower AC and GC than HHZ, implying that the palatability of LYPJ and YLY1 was not good enough to suit the preference of consumers. Our study suggests that strategies for grain quality improvement in super hybrid rice should be focused on appearance and palatability.

Previous studies showed that the N application could increase milling efficiency and nutritional value (PC) in rice grains and there was a positive relationship between the PC and N application rate [20, 23, 24]. Furthermore, Wang et al. [24] stated that the increased PC from the higher N application rate depended on increased TNU. However, in the present study, although the total N application rate was lower under SSNM than under FTNM by 20 and 15% in early and late season, respectively (**Table 2**), no significant differences were observed in N uptake (TNU and NUFG) in rice crops as well as milling efficiency and nutritional value in rice grains between SSNM and FTNM. Our results imply that replacing FTNM with SSNM can reduce N input without sacrificing grain quality in rice production.

It is well known that early season rice generally has poorer grain quality than late season rice and the poorer grain quality of early season rice is to a great extent attributed to the higher daily mean temperature during grain-filling period [25]. Consistently, in the present study, average daily mean temperature during grain-filling period across three rice cultivars was about 5°C higher in early season than in late season and grain quality was generally poorer in early season than in late season. More interestingly, we found that TNU and NUFG were significantly lower in early season than in late season. As mentioned above, higher N uptake in rice crops can lead to a higher grain PC, which may consequently result in a higher grain milling efficiency [20, 24]. Therefore, in this study, variation in N uptake was partly responsible for the seasonal differences in milling efficiency and nutritional value. Daily temperature is one of the factors influencing rice N uptake under favorable growth conditions and adequate N supply [36]. In general, higher daily temperature leads to a higher rice N uptake rate. Our previous study showed that daily temperature during the early growth stage was lower in early season than in late season, which resulted in that N uptake was lower in early season than that in late season [37]. This might be one reason why early season had lower TNU and NUFG than late season in the present study. Another reason for the seasonal variation in N uptake might be the seasonal changes in the N application rate under SSNM, which was 8% lower in early season than in late season (**Table 2**). These results also indicate that SSNM can achieve a good match of N supply with crop demand.

In addition, we observed that the interactive effects between cultivar and season on grain quality traits were generally significant. It is not surprise because (1) the seasonal variation in average daily mean temperature during grain-filling period was different between the super hybrid rice cultivars (5.9°C) and the popular inbred rice cultivar (4.6°C) (**Figure 1b** and **c**) and (2) the temperature effects on grain quality traits are cultivar-dependent [25, 38]. For example, Zhong et al. [25] found that under high temperature, GC decreased or remained little changed for cultivars with higher amylase content and increased for cultivars with lower amylase content. A similar result was also observed in the present study (**Table 4**). Namely, high temperature in early season decreased GC for LYPJ, which had higher amylase content and increased GC for YLY1, which had lower amylase content.

## **5. Conclusions**

YLY1 than in HHZ, because LYPJ and YLY1 had equal PC compared with HHZ. Moreover, it has been reported that there are positive relationships between RW with PCRG and DC [16, 17]. Therefore, the poorer appearance (higher PCRG and DC) in LYPJ and YLY1 might also be associated with their higher RW. These results also reveal that it may be difficult to achieve a synchronous improvement in milling efficiency and appearance in super hybrid rice. Among the cooking and eating quality traits, GT is often considered as an indicator affecting the cooking time of rice, for rice with higher GT requires a longer time to cook [31]. This point, however, is uncertain. Bhattacharya and Sowbhagya [32] observed that water uptake and hence the cooking time was strongly influenced by the surface area per unit weight. Other workers have also observed that water uptake of rice at boiling temperature is not related to GT but it is related to grain size and shape [33, 34]. In the present study, significant differences were observed both in GT and in grain shape between LYPJ and YLY1 with HHZ, suggesting that further studies are required to understand the difference in cooking characteristics between them. AC and GC have been considered the key indicators relating to palatability [31, 35]. Generally, consumers, especially in China, favor the rice with moderate AC and GC [25]. HHZ is such a cultivar. In the present study, LYPJ and YLY1 had largely higher or lower AC and GC than HHZ, implying that the palatability of LYPJ and YLY1 was not good enough to suit the preference of consumers. Our study suggests that strategies for grain quality improvement in

Previous studies showed that the N application could increase milling efficiency and nutritional value (PC) in rice grains and there was a positive relationship between the PC and N application rate [20, 23, 24]. Furthermore, Wang et al. [24] stated that the increased PC from the higher N application rate depended on increased TNU. However, in the present study, although the total N application rate was lower under SSNM than under FTNM by 20 and 15% in early and late season, respectively (**Table 2**), no significant differences were observed in N uptake (TNU and NUFG) in rice crops as well as milling efficiency and nutritional value in rice grains between SSNM and FTNM. Our results imply that replacing FTNM with SSNM

It is well known that early season rice generally has poorer grain quality than late season rice and the poorer grain quality of early season rice is to a great extent attributed to the higher daily mean temperature during grain-filling period [25]. Consistently, in the present study, average daily mean temperature during grain-filling period across three rice cultivars was about 5°C higher in early season than in late season and grain quality was generally poorer in early season than in late season. More interestingly, we found that TNU and NUFG were significantly lower in early season than in late season. As mentioned above, higher N uptake in rice crops can lead to a higher grain PC, which may consequently result in a higher grain milling efficiency [20, 24]. Therefore, in this study, variation in N uptake was partly responsible for the seasonal differences in milling efficiency and nutritional value. Daily temperature is one of the factors influencing rice N uptake under favorable growth conditions and adequate N supply [36]. In general, higher daily temperature leads to a higher rice N uptake rate. Our previous study showed that daily temperature during the early growth stage was lower in early season than in late season, which resulted in that N uptake was lower in early season than that in late season [37]. This might be one reason why early season had lower TNU and NUFG than late season in the present study. Another reason for the seasonal variation in N

super hybrid rice should be focused on appearance and palatability.

120 Advances in International Rice Research

can reduce N input without sacrificing grain quality in rice production.

It is concluded that (1) strategies for grain quality improvement in super hybrid rice should be focused on appearance and palatability and (2) replacing FTNM with SSNM can reduce N input without sacrificing grain quality in rice production.

## **Acknowledgements**

This study was supported by the Earmarked Fund for China Agriculture Research System (Grant No. CARS-01).

## **Author details**

Min Huang1 \*, Shuanglü Shan1 , Jiana Chen1 , Fangbo Cao1 , Ligeng Jiang1, 2 and Yingbin Zou1

\*Address all correspondence to<EMAIL_ADDRESS>
1 Southern Regional Collaborative Innovation Center for Grain and Oil Crops (CICGO), Hunan Agricultural University, Changsha, China

2 Key Laboratory of Crop Cultivation and Farming System, Guangxi University, Nanning, China

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## **The Deep Purple Color and the Scent are Two Great Qualities of the Black Scented Rice (***Chakhao***) of Manipur The Deep Purple Color and the Scent are Two Great Qualities of the Black Scented Rice (***Chakhao***) of Manipur**

Ibemhal Devi Asem, Rajkumar Imotomba and Pranab B. Mazumder and Pranab B. Mazumder Additional information is available at the end of the chapter

Ibemhal Devi Asem, Rajkumar Imotomba

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67193

#### **Abstract**

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