The main objective of this study was to produce the functionally improved whey protein hydrolysate with high bioaccessible antioxidant activity. The hydrolysate with highest antioxidant activity, mainly composed of hydrophilic antioxidant peptides and suitable for preventing oxidation in polar food matrices, was produced by tryptic hydrolysis conducted at 37°C and an enzyme/substrate (E/S) ratio of 0.5%. The hydrolysate exerted significantly improved antioxidant activity (80.0%), digestibility (95.9%) and bioaccessibility (124.6%) compared to the native whey proteins (32.1%, 87.1% and 106.3%, respectively) as widely used food supplement. The high bioaccessibility indicates the preservation of hydrolysate bioactivity during the process of gastrointestinal digestion, as a particular challenge in its application.

The aim of this study was to examine the bioactive potential of hydrolysate powders produced by enzymatic and microbial hydrolysis of whey proteins followed by spray drying, in order to reveal which one of these processes result in a product with significantly improved functional properties. Hydrolysate powders produced by the two different biotechnological processes were compared based on their antioxidant (DPPH and FTC), antibacterial as well as erythrocyte membrane stabilizing activities. The performed tests revealed that the concentration of at least 178.4 mg mL-1 of the whey protein hydrolysate powder, produced by tryptic digestion, could inhibit the process of lipid peroxidation by 50 %, suppress the microbial contamination caused by S. aureus ATCC25923, B. cereus ATCC 11778 and L. monocytogenes, and provide the antioxidant and membrane stabilizing activities greater than 50 %. On the other hand, the hydrolysate powder obtained by whey fermentation at the concentration of at least 811.5 mg mL-1 achieved 50 % of all tested bioactivities, with the emphasis on the significantly more pronounced antibacterial activity against all tested strains. In that sense, tryptic hydrolysis could be highlighted as an optimal process that provides production of the whey hydrolysate with pronounced bioactive properties that could be considered as a very promising natural food supplement.