Abstract: The changes in the release and antioxidant activity of bioactive components from six kinds of black foods (black rice, black tartary buckwheat, rye, black soybean, black gram, black millet) during in vitro simulated gastrointestinal digestion process were investigated. The results showed that after 2 h simulated gastric digestion, the highest release rates of polyphenols and flavonoids were observed from black millet and black soybean, reaching 28% and 41%, respectively. On the other hand, rye and black gram showed the highest release rates of both compound classes (113% and 52%) after another 2 h of simulated intestinal digestion. Furthermore, black soybean, black millet and black rice exhibited the highest increase in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (114%), ferric ion reducing antioxidant power (FRAP) (31%) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity (28%) during simulated gastric digestion, while the highest increase in DPPH radical scavenging activity (161%), FRAP activity (124%) and ABTS radical scavenging activity (199%) were observed for black tartary buckwheat, black millet and black rice during simulated intestinal digestion. Simulated digestion of six kinds of black foods with pepsin, tyrisin and bile significantly enhanced the release of polyphenols and flavonoids and antioxidant activity. In particular, black rice possessed the strongest antioxidant activity both before and after digestion; after gastrointestinal digestion, its antioxidant activity was determined to 4 531.79 μmol Trolox/100 g md in DPPH radical scavenging assay, 3 729.69 μmol Trolox/100 g md in FRAP assay, and 3 727.14 μmol Trolox/100 g md in ABTS radical scavenging assay, 200%, 171% and 383% higher than those before digestion, respectively. Black rice is therefore a promising black food.

Key words: black food, in vitro simulated gastrointestinal digestion, antioxidant activity, polyphenols, flavonoids