ripe, freshly collected, high-quality honey at 20 °c (68 °f) should flow from a knife in a straight stream, without breaking into separate drops. after falling down, the honey should form a bead. the honey, when poured, should form small, temporary layers that disappear fairly quickly, indicating high viscosity. if not, it indicates honey with excessive water content of over 20%, not suitable for long-term preservation. in jars, fresh honey should appear as a pure, consistent fluid, and should not set in layers. within a few weeks to a few months of extraction, many varieties of honey crystallize into a cream-colored solid. some varieties of honey, including tupelo, acacia, and sage, crystallize less regularly. honey may be heated during bottling at temperatures of 40–49 °c (104–120 °f) to delay or inhibit crystallization. overheating is indicated by change in enzyme levels, for instance, diastase activity, which can be determined with the schade or the phadebas methods. a fluffy film on the surface of the honey (like a white foam), or marble-colored or white-spotted crystallization on a container's sides, is formed by air bubbles trapped during the bottling process. a 2008 italian study determined that nuclear magnetic resonance spectroscopy can be used to distinguish between different honey types, and can be used to pinpoint the area where it was produced. researchers were able to identify differences in acacia and polyfloral honeys by the differing proportions of fructose and sucrose, as well as differing levels of aromatic amino acids phenylalanine and tyrosine. this ability allows greater ease of selecting compatible stocks. nutrition honeynutritional value per 100 g (3.5 oz)energy1,272 kj (304 kcal)carbohydrates82.4 gsugars82.12 gdietary fiber0.2 g fat0 g protein0.3 g vitaminsquantity %dv†riboflavin (b2)3% 0.038 mgniacin (b3)1% 0.121 mgpantothenic acid (b5)1% 0.068 mgvitamin b62% 0.024 mgfolate (b9)1% 2 μgvitamin c1% 0.5 mg mineralsquantity %dv†calcium1% 6 mgiron3% 0.42 mgmagnesium1% 2 mgphosphorus1% 4 mgpotassium1% 52 mgsodium0% 4 mgzinc2% 0.22 mg other constituentsquantitywater17.10 g full link to usda database entry units μg = micrograms • mg = milligrams iu = international units †percentages are roughly approximated using us recommendations for adults. one hundred grams of honey provides about 1,270 kj (304 kcal) of energy with no significant amounts of essential nutrients. composed of 17% water and 82% carbohydrates, honey has low content of fat, dietary fiber, and protein. sugar profile a mixture of sugars and other carbohydrates, honey is mainly fructose (about 38%) and glucose (about 32%), with remaining sugars including maltose, sucrose, and other complex carbohydrates. its glycemic index ranges from 31 to 78, depending on the variety. the specific composition, color, aroma, and flavor of any batch of honey depend on the flowers foraged by bees that produced the honey. one 1980 study found that mixed floral honey from several united states regions typically contains the following: fructose: 38.2% glucose: 31.3% maltose: 7.1% sucrose: 1.3% water: 17.2% higher sugars: 1.5% ash: 0.2% other/undetermined: 3.2% this means that 55% of the combined fructose and glucose content was fructose and 45% was glucose, which enables comparison with the essentially identical result (average of 56% and 44%) in the study described below: a 2013 nmr spectroscopy study of 20 different honeys from germany found that their sugar contents comprised: fructose: 28% to 41% glucose: 22% to 35% the average ratio was 56% fructose to 44% glucose, but the ratios in the individual honeys ranged from a high of 64% fructose and 36% glucose (one type of flower honey; table 3 in reference) to a low of 50% fructose and 50% glucose (a different floral source). this nmr method was not able to quantify maltose, galactose, and the other minor sugars as compared to fructose and glucose. medical use and research