Abstract: Lactobacillus rhamnosus and Lactobacillus helveticus were separately added to Cheddar cheese to prepare probiotic cheese, whose in vivo antioxidant activity was studied using an aging mouse model. Antioxidant peptides were isolated and purified from the cheeses for structural identification by high performance liquid chromatography-mass spectrometry (HPLC-MS) and for evaluation of in vivo metabolic pathways and stability by a fluorescence labeling tracer method. The results showed that compared with the aging model group, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the serum of mice gavaged with water-soluble proteins extracted from the probiotic cheeses significantly increased (P < 0.05), and the water-soluble proteins extracted from the cheese containing Lactobacillus helveticus had a stronger in vivo antioxidant effect, increasing the activities of serum SOD, CAT, and GSH-Px by 45.98%, 35.33%, and 37.93%, respectively compared to the aging model group and exhibiting no significant difference in any of these antioxidant enzyme activities compared to the normal control and VC groups (P > 0.05). A total of 6 antioxidant peptides were identified from the cheese with Lactobacillus helveticus, and among them the peptide QPHQP had the highest antioxidant activity. QPHQP exerted antioxidant activity in various organs of the body in the following order: stomach and intestine → kidney, liver and lung → heart and spleen → brain. Among all organs except for the gastrointestinal tract, the accumulation of the fluorescently labeled peptide in the liver was the highest, and it decreased slowly. Therefore, the probiotic Cheddar cheeses had antioxidant activity in vivo. When it entered the body, the antioxidant peptide passed through the gastrointestinal tract and reached its target organs through the blood circulation, mainly accumulating in the liver to play an antioxidant role.

Key words: Cheddar cheese; antioxidant peptide; in vivo activity; structure; in vivo metabolism