Abstract: This study aimed to explore the changes in the phenolic content and antioxidant activity of black hulless barley processed by different methods after in vitro gastrointestinal digestion. The tested methods included boiling, stir frying, extrusion puffing, explosion puffing and fermentation. After digestion, the phenolic content of the five processed samples increased 1.99–2.44 folds (P < 0.05). The total flavonoid content of all processed samples except the one subjected to explosion puffing decreased by 34%–70% (P < 0.05). Phloretin, protocatechin, p-coumaric acid and ferulic acid were the major phenolic acids, and catechins were the major flavonoids after in vitro gastrointestinal digestion. Meanwhile, the contents of the major monomeric phenolic acids in the five processed samples significantly increased (P < 0.05), whereas the contents of the monomeric flavonoids significantly declined (P < 0.05). The antioxidant potency composite (APC) indexes of the processed samples declined in the following order: extrusion puffing (89.61%), fermentation (88.16%), boiling (77.67%), explosion puffing (76.86%) and stir frying (75.13%). In conclusion, the contents of total phenols and total flavonoids were the highest in black hulless barley subjected to explosion puffing, while the sample subjected to extrusion puffing had the highest antioxidant activity. This study can provide a scientific guideline for selecting different processing methods for the development of hulless barley products to meet diverse consumer demands.

Key words: black hulless barley; processing methods; in vitro gastrointestinal digestion; phenolic compounds; antioxidant activity