Hydrolysis of whey protein as a useful approach to obtain bioactive peptides and a β-Lg fraction with different biotechnological applications

Abstract

Most of the studies related to the susceptibility of the main bovine whey proteins to the action of cardosins of Cynara cardunculus have underestimated the potential of these proteases to hydrolyse β-Lactoglobulin (β-Lg). These works used the one-factor-at-a-time methodology, which ignores the interactions and can lead to misleading conclusions. In this work, the hydrolysis of bovine whey protein, exploiting the joint action of cardosins A and B of C. cardunculus, was optimised. For that purpose, a second-order rotatable design (with two variables at five levels) was used to study the combined effect of pH and temperature on the degree of hydrolysis (DH), the number of peptides generated and the angiotensin I-converting enzyme (ACE)-inhibitory activity.The complete hydrolysis of α-Lactalbumin (α-La) was achieved at pH 6.99/35.86 °C and pH 5.01/64.14 °C, and contrary to the previous studies, cardosins were able to hydrolyse β-Lg (up to ~40%) at pH 6.29/50 °C. In addition, the statistical analysis revealed that the same pH and temperature values that led to a minimum DH for α-La also provide a maximum DH for β-Lg.At pH 5.3 and 60 °C, we have obtained abundant peptides with high angiotensin I-converting enzyme (ACE)-inhibitory activity, but also a non-hydrolysed β-Lg. So, the purification and identification of the bioactive peptides, produced under these hydrolysis conditions, was performed. Moreover, the biotechnological potential of the β-Lg obtained was successfully proved for 3 promising applications: heat-induced gels, nanofibrils (self-assembly) and microparticles (spray-dryer).