1. Introduction
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INFECTION, SECONDARY
Much attention has been paid to the health benefits of including fruits and vegetables in the diet. However, for the compounds responsible for this beneficial effect to be effective at the level of the human organism, they must be available for absorption after digestion. In this sense, in vivo studies are needed to demonstrate the bioavailability of these compounds and their physiological activity. In order to provide information in this regard, this study collects data on the levels of vitamin C (VC) and naringenin (NAG) in the blood serum of the 11 volunteer participants in this trial, before and after consuming two different grapefruit juices. The juices were prepared by rehydrating the grapefruit powder obtained by freeze-drying (FD) the fruit puree or by spray-drying (SD) the liquefied grapefruit. No significant differences (Consumer attention is currently focused on healthy eating habits. Fruit juices can be clearly included in a healthy diet as they contain different health-promoting bioactive compounds, mainly VC and phenolics, which contribute to antioxidant capacity. Nevertheless, the consumer also looks for high-quality, stable and easy to handle foods. In this sense, fruit powder obtained from its edible part may be an interesting alternative to be consumed, for example, as juice after rehydration. Different techniques can be used to obtain powdered foods, with FD and SD providing the highest quality products. A lot of studies could be cited that have been carried out to evaluate the impact of different food processes on product quality. Nevertheless, the studied quality attributes are related to the composition, physical, chemical or biochemical properties or sensory aspects, among others. Nonetheless, we have not found any study investigating the impact of the processes on the bioavailability of the bioactive compounds potentially responsible for the functional value of foods.For the bioactive compounds to be effective in the human organism, they need to be released during digestion and then absorbed in a certain amount in the intestine. Bioavailability is commonly defined as the fraction of a given food constituent that reaches systemic circulation [The bioavailability of bioactive compounds depends, apart from the mastication and the level of intake, on its nature, the composition and rheological properties of the food matrix and the interactions among the different components, among others [The biological functions of VC depend upon its ability to act as an electron donor. Among these, it acts as a cofactor for a variety of enzymes with critical functions throughout the body, functions as a highly effective water-soluble antioxidant, and it is suggested that is involved in the regeneration of vitamin E in vivo [Phenolics are secondary metabolites produced by plants against stress conditions such as injury, infection, and UV radiation [Grapefruit is a source of VC and phenolics, flavonoids among them. Specifically, the main flavonoids are glycosides naringin, followed by narirutin [This study was designed given the interest in providing more and more information on the human bioavailability of different bioactive compounds and the scarce information available on this subject. The objective was to provide information on the bioavailability of VC and the main flavonoids in grapefruit juice, recovered as NAG in circulating blood, depending on the process used to obtain it.