Identification and characterization of antioxidant peptides obtained from the bioaccessible fraction of α-lactalbumin hydrolysate

Whey is an abundantand sustainable source of bioactive peptides obtained from cheese making process. Whey proteins such as alpha-lactalbumin can be biologically active when the bioactive peptides encrypted in the amino acid sequence of the native protein are released by enzymatic hydrolysis. In the present work, the identification, sequence analysis, and antioxidant activity of bioaccessible peptides from alpha-lactalbumin alcalase-hydrolysate was assessed. Antioxidant activity (ABTS, ORAC, and HORAC) of alpha-lactalbumin showed a significant increase (p < 0.05) after the enzymatic treatment with alcalase and this capacity increased even more after the simulation of the gastrointestinal digestion process. Peptides contained in the gastrointestinal digest of alpha-lactalbumin hydrolysate were separated by preparative RP-HPLC (55 fractions), and three peptides were identified by LC-MS/MS analysis from selected fractions: IWCK-DDQNPH (MW: 1254.54 Da) f(59-68), KFLDDDLTDDIM (MW: 1439.64 Da) f(79-90), DKFLDDDLTDDIM (MW: 1554.67 Da) f(78-90). Among the chemically synthesized peptides, IWCKDDQNPH showed the highest antioxidant capacity determined by ORAC, ABTS, and HORAC assays (IC50 0.015 +/- 0.002, 0.45 +/- 0.02, and 1.30 +/- 0.05 mg/ml, respectively) and this activity may be related to the amino acid sequence. This is the first report where these bioaccessible peptides from alpha-lactalbumin hydrolysate were identified. The alpha-lactalbumin hydrolysate could be employed as a functional antioxidant ingredient. Practical Application: The present work studied the bioaccessibility of antioxidant peptides from an alpha-lactalbumin alcalase-hydrolysate by identifying three novel bioaccessible peptides responsible for the antioxidant capacity, providing evidence of the hydrolysate potential as an antioxidant ingredient in the formulations of functional foods and/or food supplements.

Automated summary

The study demonstrated a significant increase in antioxidant activity of alpha-lactalbumin after enzymatic treatment with alcalase, which further improved after simulating gastrointestinal digestion. Three novel bioaccessible peptides with antioxidant capacity were identified from the gastrointestinal digest, suggesting the potential of alpha-lactalbumin hydrolysate as an antioxidant ingredient in functional foods.