Modification of interactions between selected volatile flavour compounds and salt-extracted pea protein isolates using chemical and enzymatic approaches

Abstract

Effects of chemical (acetylation and succinylation) and enzymatic (Alcalase) modifications on the binding properties of salt-extracted pea protein isolates (PPIs) to 2-octanone, octanal, hexyl acetate and dibutyl disulfide were monitored using GC/MS and related to changes in protein structure, based on differential scanning calorimetry and native-PAGE analyses. Addition of acetic and succinic anhydrides from zero to one gram per gram of protein gradually released the bound octanal and hexyl acetate mainly due to the loss of reactive NH2 and OH groups and dissociation of protein inherent structure. Initial addition of these dicarboxylic acid anhydrides (<0.1 g) resulted in partial denaturation of PPIs and increased binding for 2-octanone and dibutyl disulfide; however, further addition of anhydrides reduced retention of these flavour compounds probably due to extensive protein denaturation and masking of free SH groups on the protein. The binding of dibutyl disulfide was found to be positively correlated with the number of free sulfhydryl groups on acylated PPIs inferring potential sulfhydryl-disulfide interchange reactions. Enzymatic hydrolysis of PPIs by Alcalase released bound ketone and ester flavours; however, the retention levels for aldehyde and disulfide flavours were enhanced. A strong relationship was found between protein-flavour binding affinities, the type of flavour and the structure of the protein as affected by different protein modification methods.