Soy protein hydrolysates fermentation: Effect of debittering and degradation of major soy allergens

The debittering effect of induced liquid state fermentation (Lactobacillus perolens, Rhizopus oryzae, and Actinomucor elegans) on different soy protein hydrolysates has been investigated. The hydrolytic action was monitored by SDS-PAGE and degree of hydrolysis analyses. Sensory perception using quantitative descriptive analysis (QDA), employing multivariate statistical principal component analysis (PCA), techno-functional properties, and the microbial competitiveness (MALDI-TOF-MS) have been evaluated. SDS-PAGE profiles evidenced that the enzyme preparations degraded most of major soy allergens (v-conglycinin, glycinin), while subsequent fermentation did not further change the profiles. All strains investigated effectively reduced bitterness to a minimum of 0.7 on a 10-cm continuous scale (0 = no perception; 10 = strong perception) compared to non-fermented hydrolysates (2.8-8.0) and untreated soy protein isolate (2.8). Protein solubility, emulsifying and oil-binding capacity as well as foaming activity and gelation behaviour were enhanced depending on the protease used; subsequent fermentation further improved foaming stability and gelation concentration. PCA of descriptive sensory data revealed that fermentation apparently upgrade the organoleptic perception by effectively decreasing the bitter taste, simultaneously reducing the beany off-flavour of soy. Consequently, enzymatic hydrolysis combined with subsequent fermentation represents a promising method for the production of hypoallergenic soy hydrolysates with pleasant taste and great technofunctionality.