Effect of solid-state fermentation on the functionality, digestibility, and volatile profiles of pulse protein isolates

Fermentation, as a clean processing technique, induces structural and compositional modifications to plant proteins, improving their functionality and nutrition. However, the effect varies depending on the level of hydrolysis, the fermenting strain, and the specific substrate used. The present work examined the effect of solidstate fermentation (SSF) by Lactobacillus plantarum, Aspergillus niger and Aspergillus oryzae of several niche market pulse (chickpea, green lentil, and faba bean) protein isolates on their functional and nutritional properties. The pulse proteins were moderately hydrolyzed to different extents (degree of hydrolysis of 9%-15%) after 48 h of fermentation, enhancing surface charge and solubility while decreasing water holding capacity and emulsion stability. Protein digestibility was reduced for all pulses which was hypothesized to be due to an increase in phenolic content caused by fermentation. Among the strains, only A. niger outgrew the natural microbiota for all pulses. Variations relating to the property changes were observed among the inocula and pulses; however, no general trend could be concluded. Fermentation produced a large variety of favourable new volatile compounds in the protein isolates.