Abstract: The aim of this work was to explore the effect of digestion on the antioxidant activity of probiotic cheese. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, reducing power and 2,2’-azino-bis(3- ethylbenzthiozoline-6)-sulphonic acid (ABTS) radical scavenging capacity were analyzed to investigate the antioxidant activity of probiotic Cheddar cheese after simulated gastrointestinal digestion, and the viable count of probiotics and polypeptide content were examined. The results showed that the antioxidant activity of cheese increased significantly after simulated gastrointestinal digestion (P < 0.05), and the antioxidant activity of cheese containing both B. bifidum 07-300B and L. acidophilus 1.0357 were significantly higher than that of any other group (P < 0.05). Moreover, the DPPH radical scavenging capacity, reducing power and ABTS+· scavenging capacity ((82.76 ± 3.19)%, 0.828 ± 0.021 and (44.84 ± 1.36)%) were increased by 71.42%, 62.35% and 51.69%, respectively, and the polypeptide content ((2.80 ± 0.02) mg/mL) was also significantly increased by 39.30% (P < 0.05) when compared with that before digestion, with the polypeptides with molecular weight < 3 kDa presenting the highest antioxidant activity. The number of viable probiotic bacteria in cheese decreased significantly by 16.93% after digestion. Therefore, the antioxidant activity of cheese could be improved by generating small molecule polypeptides with antioxidant activity after simulated gastrointestinal digestion.

Key words: cheese, probiotics, simulated gastrointestinal digestion, antioxidant activity, polypeptide