Title : Evaluation of Gamma Irradiation and Sterilization on the Enzymatic Hydrolysis and Antioxidant Capacity of Whey Proteins
Whey is a by-product obtained during the manufacture of cheese. Among proteins, whey contains mainly α-lactalbumin (α-LA) and β-lactoglobulin (β-LG). In recent years there has been great interest in the identification and characterization of bioactive peptides obtained from the enzymatic hydrolysis of whey proteins. These peptides have different bioactivities such as antihypertensive, antioxidant, antimicrobial and immunomodulatory activity, among others. The objective of this study was to determine the effect of gamma irradiation and sterilization, as a pretreatment for the enzymatic hydrolysis of whey with trypsin and papain, and evaluate the relationship with the antioxidant capacity of the peptides obtained. The enzymatic hydrolysis was carried out on one whey sample without pretreatment, four samples subjected to gamma radiation at different doses (5, 10, 15 and 20 kGy) and one sterilized sample at 121 °C for 15 min. Samples were hydrolyzed for 9 h with trypsin and papain at the optimal pH conditions for each enzyme, with an E: S ratio of 1:10 (w / w) and at 37 °C. All experiments were performed with at least two replicates. The degree of hydrolysis of the different hydrolysates was determined with the OPA method and the antioxidant capacity was measured by the ABTS and DPPH method, using Trolox equivalent antioxidant capacity (TEAC) values. The results showed that the whey subjected to the sterilization pretreatment and hydrolyzed with trypsin showed the highest values of degree of hydrolysis and antioxidant capacity, which were 3.46% ± 0.10 and 2030.7 ± 14,7 µM of Trolox equivalent (TEAC) respectively. Besides, a correlation was found between the degree of hydrolysis and the antioxidant capacity. These results show that sterilization and the use of enzymes for the hydrolysis of whey could be an alternative to improve its antioxidant capacity.