In Vitro Availability of Flavonoids and Other Phenolics in Orange Juice

Abstract

Hand-squeezed navel orange juice contains 839 mg/L phenolics, including flavanones, flavones, and hydroxycinnamic acid derivatives. The flavanones are the main phenolics in the soluble fraction (648.6 mg/L) and are also present in the cloud fraction (104.8 mg/L). During refrigerated storage of fresh juice (4 °C), 50% of the soluble flavanones precipitate and integrate into the cloud fraction. Commercial orange juices contain only 81−200 mg/L soluble flavanones (15−33%) and the content in the cloud is higher (206−644 mg/L) (62−85%), showing that during industrial processing and storage the soluble flavanones precipitate and are included in the cloud. An in vitro simulation of orange juice digestion shows that a serving of fresh orange juice (240 mL) provides 9.7 mg of soluble hesperidin (4‘-methoxy-3‘,5,7-trihydroxyflavanone-7-rutinoside) and 4.7 mg of the C-glycosylflavone vicenin 2 (apigenin, 6,8-di-C-glucoside) for freshly squeezed orange juice, whereas pasteurized commercial juices provide 3.7 mg of soluble hesperidin and a higher amount of vicenin 2 (6.3 mg). This means that although orange juice is a very rich source of flavanones, only a limited quantity is soluble, and this might affect availability for absorption (11−36% of the soluble flavanones, depending on the juice). The flavanones precipitated in the cloud are not available for absorption and are partly transformed to the corresponding chalcones during the pancreatin−bile digestion. Keywords: Orange juice; flavonoids; processing; flavanones; flavonols; caffeic acid derivatives; availability; solubility