Impact of ultrasound pretreatment on whey protein hydrolysis by vegetable proteases

• Whey proteins are affected by ultrasound pre-treatment increasing their susceptibility to bromelain hydrolysis.
• Lower level of ultrasound intensity used increase the ACE inhibition of bromelain hydrolysates and reduce hydrolysis time.
• Ultrasound pretreatment seems to be enzyme-dependent.
• The denaturation and aggregation phenomenon induced by ultrasound pretreatment were evaluated using DSC and DC respectively.

The ultrasound treatment on whey protein before enzymatic hydrolysis using vegetable proteases was studied. Ultrasound density, temperature, and pretreatment time effects were evaluated on enzymatic degree of hydrolysis, release of Angiotensin I-Converting Enzyme (ACE) inhibitors, and antioxidant activity of the hydrolysates generated. In addition, thermal properties as measured by Differential Scanning Calorimetry (DSC) and changes in secondary structure by circular dichroism (CD) were measured. The results showed that ultrasound density was the only factor that exerted a significant effect on proteolysis increasing the ACE inhibition by 13% and a 95% reduction of hydrolysis time in bromelain hydrolysates, but did not improve the ACE inhibition on papain hydrolysates. Observed changes in denaturation enthalpy (ΔH), reduction of reactive thiol groups, and changes in secondary structure suggest protein rearrangements and aggregate formation. The effect of ultrasound on the whey protein structure produced changes increasing the bioactivity of hydrolysates that could enhance the enzymatic hydrolysis process.Industrial relevanceWhey proteins are an important source of bioactive peptides. However, due to their globular structure, they are a complex substrate for enzymatic hydrolysis. Ultrasonic pretreatment could induce changes increasing susceptibility to enzymatic hydrolysis resulting in production of more bioactive peptides. Therefore, treatment of whey proteins with ultrasound waves before enzymatic hydrolysis, offers higher efficiency of enzymatic bioconversion of proteins and production of new biologically active peptide mixtures.