Storage stability and simulated gastrointestinal release of spray dried grape marc phenolics.

Abstract

tMaltodextrin (MD), whey protein isolate (WPI) and pea protein isolate (PPI) have been usedin this work as carrier agents in the spray drying of grape marc extract, and the obtainedmicroparticles have been characterized in terms of drying yield, morphology (SEM), sizedistribution, chemical structure (FTIR), chemical composition (total phenolic and antho-cyanin content), and antioxidant activity (ORAC). WPI was found to be the most effectivecarrier for optimizing drying yield, requiring less than 0.5:1 carrier:extract solids ratio toachieve the usual 50% yield benchmark. In vitro gastrointestinal release of total phenolicsand anthocyanins indicated Fickian diffusion, with the Higuchi and Korsmeyer–Peppas mod-els providing the best fit for the data. An accelerated stability test carried out at 40 and 60◦Crevealed first-order kinetics for anthocyanin degradation. WPI formulated microparticlesshowed severe degradation at 40 and especially 60◦C (complete degradation after 4 days),followed by MD and PPI microparticles. Similarly, a long term stability test carried out at roomtemperature (25◦C) over six months showed that total phenolic content did not diminishfor any of the carriers, but anthocyanin content suffered a 20% loss after 6 months for PPIand MD formulated samples, and a 50–65% loss for WPI formulated samples.