Impact of in vitro gastrointestinal digestion on upcycled blackcurrant dried extract: anthocyanins profile and antioxidant activity behavior

Pomaces, the major by-product of fruit juice processing industries, is rich in bioactive compounds. Among them, polyphenols boost the body's antioxidant capacity, improving cardiovascular health, reducing the risk of diabetes and inflammation, and promoting intestinal microbiota health. Blackcurrant (Ribes nigrum L.) is a highly antioxidant berry rich in anthocyanins, a polyphenols class that also gives the fruit a black-purple color. Thus, blackcurrant pomace polyphenols have the potential to be functional food ingredients that can enhance sustainability in the agri-food processing chain with health benefits. In order to have a beneficial effect on health, polyphenols must be bioaccessible. This means they must be released from the food matrix during gastrointestinal digestion (GID) and available for absorption in the gut.This study aimed to assess the bioaccessibility of anthocyanins and the antioxidant activity of polyphenolic extract from blackcurrant pomace. For this purpose, an enzymatic method was used to release the polyphenols from the pomace, which were then spray-dried. The INFOGEST 2.0 protocol was used to simulate the in vitro GID of the powder. The anthocyanins profile (HPLC-DAD), total phenolic content (TPC, Folin-Ciocalteu method), antioxidant capacity (ABTS, DPPH), and cytotoxicity (PrestoBlue assay) were evaluated.The blackcurrant powder extract initially contained over 900 mg/L of total anthocyanins. The major compounds are cyanidin-3-O-glucoside (54%), pelargonidin-3-O-glucoside (19%), and delphinidin-3-O-glucoside (18%). The anthocyanins remained stable during the gastric phase of GID, with a full recovery index of 20% and 12% for cyanidin-3-O-glucoside. Still, they drastically decreased in the intestinal stage due to a pH change that caused a break in the anthocyanin B-ring. The TPC of the extract significantly reduced during the oral and gastric phases but increased slightly during the intestinal phase, with a 19% recovery index. The extract's antioxidant activity decreased, resulting in a bioaccessibility index of 19% and 23% for ABTS and DPPH scavenging activity, respectively. Despite a decrease in TPC along the GID, the extract still exhibited antioxidant capacity due to the existence of various phenolic compounds, specifically hydroxybenzoic and hydroxycinnamic acids, resulting from the degradation/transformation of anthocyanins3. A 2.5% (w/v) of antioxidant extract powder is safe for food formulations.Thus, this work provides insights into the effects of GID on anthocyanins and the potential use of blackcurrant pomace as a source of bioactive ingredients, promoting a circular economy.