Pulp in Shop-Bought Orange Juice Has Little Effect on Flavonoid Content and Gut Bacterial Flavanone Degradation In Vitro

Abstract

Orange juice is an important source of flavanones in the Western diet. However, little is known of the variation in flavanone content of shop-bought orange juice with pulp (OJP) or without pulp (OJ), nor the impact of pulp on the fate of flavanones in the gut. Total phenols, total flavonoids, antioxidant capacity, hesperidin and narirutin, and dietary fibre were measured in six orange juice brands sold as OJP and OJ. The inclusion of pulp had little impact on fibre content. Apart from total phenols (OJ: 208.4 ± 10.7 μg gallic acid equivalents (GAE) ml−1; OJP: 225.9 ± 16.7 μg GAE ml−1, P < 0.05), there were no differences between OJ and OJP. The fate of flavanones in OJ and OJP (Tropicana) were further compared using in vitro gastrointestinal (GI) models. After in vitro upper GI digestion, recovery of hesperidin was higher in OJ compared with OJP (89 ± 6 vs. 68 ± 3%, P = 0.033). After 2 h colonic fermentation, hesperidin was 1.2 fold higher in OJP than OJ. However, after 24 h colonic fermentation there was no significant difference between juices in terms of hesperidin, hesperetin, narirutin, naringenin and catabolites. In conclusion, the amount of pulp included in these shop-bought orange juices had little impact on flavanone metabolism in models of the GI tract. The effects of greater amounts of orange pulp remain to be determined.