Effects of food matrix elements (dietary fibres) on grapefruit peel flavanone profile and on faecal microbiota during in vitro fermentation

Citrus fruits are a good source of flavanones. The present study aimed to assess the effect of food matrix elements [dietary fibres (DFs)] on the flavanone profile of grapefruit peel (GFP) and on the gut microbiota during in vitro digestion and simulated colonic fermentation. The contents of low-molecular-weight metabolites (dihydrocaffeic acid and 3-phenylpropionic acid) were increased by pectin, konjac and chitosan in medium- and high-viscosity matrices. Compared with the GFP group, the counts of Lactobacillus spp. and Clostridium leptum were significantly increased in medium-viscosity food matrices (konjac and chitosan) (p < 0.05). Moreover, the acetic and propionic acid contents were significantly elevated in the GFP + DF groups after 12 h of fermentation (p < 0.05). GFP flavanones were retained by DF, and the total phenolic content (TPC) and antioxidant potency composite (APC) index decreased during in vitro digestion. These findings indicate that medium-viscosity DFs (konjac and chitosan) could act as key food matrix elements for the retention of polyphenols.

Automated summary

The study found that pectin, konjac, and chitosan can increase the content of low-molecular-weight metabolites in grapefruit peel, and that high-viscosity food matrices (such as konjac and chitosan) have a significant impact on gut microbiota during simulated colonic fermentation. Dietary fibers can retain flavanones in grapefruit peel.