Application of high-pressure processing as a tool to improve the hydrolysis of whey proteins using different proteases.

Whey protein; enzymatic hydrolysis; in vitro antioxidant capacity; in vitro allergenicity, antihypertensive activity.

Whey is a co-product of the dairy industry, which has a high protein content with high nutritional value and technological properties, which allow its use in a wide variety of products. These properties can be improved by enzymatic processes, capable of releasing bioactive peptides and reducing allergenicity concerning the native protein. The high hydrostatic pressure (HHP) process can improve the hydrolysis of these proteins, as it causes structural changes that facilitate proteolysis. Therefore, this study aimed to evaluate the effect of HHP on the hydrolysis of a whey protein concentrate (WPC) using different proteases. Each treatment presented its particularities regarding the effects of HHP on whey protein hydrolysis. For this reason, the thesis was divided into two chapters. The first one evaluated the effect of the application of HHP on the peptic hydrolysis of the WPC. The application of HHP was evaluated before (pretreatment - PT) and during the hydrolysis processes (assisted by hydrolysis - AH). β-lactoglobulin, which is resistant to peptic hydrolysis, was hydrolyzed by up to 98% in treatments where HHP was used. Besides, HA at 100 MPa for 35 min. exhibited a 35% reduction in soluble proteins, while in conventional hydrolysis and PTs the reduction was approximately 20% after 4 hours of reaction. HHP was also an important tool to improve the in vitro antioxidant capacity of hydrolysates. These results suggested that HA by HHP is an efficient strategy to improve peptic hydrolysis, significantly reduced the processing time, and increased hydrolysates' antioxidant activity. On the second chapter, it was investigated the use of the Novo Pro-D® (NPD) and ficin (FC) as alternative proteases for the production of hydrolysates. After selecting the best enzyme:substrate ratio, the chemical characteristics (soluble proteins, aromatic amino acids, and chromatographic profile), bioactive properties (antioxidant capacity and antihypertensive activity), and the allergenicity of the hydrolysates were evaluated in whichHHP was evaluated as a pretreatment of protein hydrolysis. NPD generated hydrolysates with a 98% reduction in soluble proteins, greater antioxidant capacity, and less immunoreactivity than FC processes. However, the pretreatment was an important tool to improve the characteristics of hydrolysates obtained by FC, and treatments at 400 MPa / 5 min and 400 MPa / 35 min resulted in a reduction of 68.81 and 85.29% of proteins, respectively. Also, hydrolysates presented greater antioxidant capacity and less allergenicity than those obtained by conventional hydrolysis. The hydrolysate's antihypertensive activity from FC caused a more pronounced vascular relaxation than the ones from NPD. Both enzymes (NPD and FC) showed high potential for the production of hydrolysates, and the use of high hydrostatic pressure as a pretreatment showed to be a promising alternative to produce hydrolysates with improved characteristics. In summary, the results altogether suggested that the right selection of the enzyme will lead to the development of the desired characteristics of hydrolysates In addition, HHP was a vital tool to improve the hydrolysis of whey proteins and the final characteristics of hydrolysates.