Determination of the bioaccessibility of compounds with antioxidant activity from orange juice subjected to an in vitro digestion system

Background and objectives: Citrus fruits, among which the orange (Citrus sinensis) stands out, have a high commercial value both fresh and in the food industry. Vitamin C is their most recognized nutrient, but they also provide phenolic compounds of vital importance to improve human health due to their antioxidant properties. However, during the digestion process, food components are constantly exposed to different physicochemical and biochemical conditions and, consequently, the bioavailability and bioactivity can be affected. The objective of the study was to determine the bioaccessibility of the phenolic profile and vitamin C in orange juice subjected to an in vitro digestion system. Methods: In vitro digestion of orange juice was performed. Porcine pepsin was used in gastric phase (pH=2 with HCl). For intestinal phase, porcine bile and pancreatin were used (pH=5.3 with NaOH). For bioaccessible phase, the membranes were filled with NaHCO (pH=7 with NaOH). The determination of total polyphenols in samples was carried out following the Folin-Ciocalteu method and the antioxidant activity, by the DPPH and FRAP methods. The profile of phenolic compounds and the content of vitamin C was determined by high performance liquid chromatography (HPLC). Results: The content of vitamin C, after in vitro digestion, decreased by 84% (only 16% of the total quantified in the juice was preserved). Of the total polyphenol content, 37% was preserved and, regarding antioxidant activity, 14 and 12% bioaccessibility was observed for DPPH and FRAP, respectively. The highest concentration of phenolic compounds was narirutin, followed by hesperidin, kaempferol, hesperitin, naringenin and quercetin. On the other hand, the highest bioaccessibility was found in hesperitin and the lowest in hesperidin (93 and 3%, respectively). Conclusions: Although the hesperidin content is high, its percentage of bioaccessibility was the lowest compared to the other phenolic compounds analyzed. The bioaccessible portion of vitamin C and the total antioxidant activity of orange juice is less than 20% of the content in the food. Therefore, it is necessary to perform in vivo experiments to provide relevant information on the real experience of the consumption of citrus beverages.