Enhanced stability of berry pomace polyphenols delivered in protein-polyphenol aggregate particles to an in vitro gastrointestinal digestion model

Stability of protein-polyphenol aggregate particles, created by complexing polyphenols from blueberry and muscadine grape pomaces with a rice-pea protein isolate blend, was evaluated in an in vitro gastrointestinal model. Recovery index (RI; % total phenolics present post-digestion) was 69% and 62% from blueberry and muscadine grape protein-polyphenol particles, compared to 23% and 31% for the respective pomace extracts. Anthocyanins RI was 52% and 42% from particles (6% and 13% from pomace extracts), and proanthocyanidins RI was 77% and 73% from particles (25% and 14% from pomace extracts), from blueberry and grape, respectively. Protein-polyphenol particle digests retained 1.5 to 2-fold higher antioxidant capacity and suppressed the expression of pro-inflammatory cytokines, iNOS, IL6, and IL1 beta, compared to unmodified extract digests, which only suppressed IL6. Protein-polyphenol particles as a delivery vehicle in foods may confer better stability during gastrointestinal transit, allow protected polyphenols to reach the gut microbiota, and preserve polyphenol bioactivity.