Mechanism of the Allergenicity Reduction of Ovalbumin by Microwave Pretreatment-Assisted Enzymolysis through Biological Mass Spectrometry

Ovalbumin (OVA) is a major allergen in hen eggs. Enzymolysis has been demonstrated as an efficient method for reducing OVA allergenicity. This study demonstrates that microwave pretreatment (MP) at 400 W for 20 s assisting bromelain enzymolysis further decreases the allergenicity of OVA, which was attributed to the increase in the degree of hydrolysis and promoted the destruction of IgE-binding epitopes. The results showed that MP could promote OVA unfolding, expose hydrophobic domains, and disrupt tightly packed alpha-helical structures and disulfide bonds, which increased the degree of hydrolysis by 7.28% and the contents of peptides below 1 kDa from 43.55 to 85.06% in hydrolysates compared with that for untreated OVA. Biological mass spectrometry demonstrated that the number of intact IgE-binding epitope peptides in MP-assisted OVA hydrolysates decreased by 533 compared to that in hydrolysis without MP; consequently, their IgG/IgE binding rates decreased more significantly. Therefore, MP-assisted enzymolysis may provide an alternative method for decreasing the OVA allergenicity.