Effect of in-vitro digestion on polyphenols extracted from pomegranate and apple by-products

Fruit processing industries generate by-products rich in polyphenols and antioxidants, but they decay due to short lifespans and inadequate management. This study aims to evaluate the impact of In-vitro digestion (IVD) on polyphenols, antioxidant potential, and polyphenolic profiles (free and bound) using HPLC–DAD in apples and pomegranate by-products. Predominant phenolic compounds in each sample found were myricetin, protocatechuic acid, and catechin. Most of the individual phenolic compounds reduced upon digestion except for gallic acid, protocatechuic acid, sinapic acid, and ferulic acid. The order of phenolic compounds and antioxidants among the fruit by-products was pomegranate peel (PPe) > pomegranate pomace (PPo) > apple pomace (AP) based on the phenolic compositions studied and antioxidant properties (DPPH, ABTS⋅+, FRAP, and reducing power activity). These by-products are high in polyphenols, and post-IVD revealed their retention and remained bioaccessible; therefore, they can be used to develop functional foods.