Elderberry pomace for food/nutraceutical product development: impact of drying methods and simulated in vitro gastrointestinal digestion on phenolic profile and bioaccessibility

The aim of this work was to develop ingredients from elderberry pomace (EP) analysing the effect of different drying methods (conventional air-drying (C), freeze-drying (F), and fluidised-bed drying (FB)) on phenolic compounds retention and their bioaccessibility. The dry pomaces were chemically characterised before and after an in vitro gastrointestinal digestion (GID). Cianidin-3-glucoside and rutin were the main phenolic compounds determined by HPLC-DAD. After GID, phenolic content and antioxidant capacity were drastically reduced regardless of the drying process. Freeze-drying better preserved the total polyphenol and monomeric anthocyanin content, and the antioxidant capacity, however, EP-C and EP-FB presented more bioaccessible antioxidant compounds than EP-F. Fluidised-bed drying generated, in a shorter drying time, a more bioaccessible granular product (EP-FB), that could be used directly in ready-to-eat foods. EP-C and EP-F products could be used as functional foods or nutraceutical ingredients. Also, the obtained elderberry products were not cytotoxic against the Caco-2 cell line.