Impacts of solid-state fermentation on functional properties of pea protein isolate

Abstract

Twelve GRAS (generally recognized as safe) microorganisms, including seven bacteria (Lactobacillus delbrueckii, Lactobacillus rhamnosus, Weissella confusa, Lactococcus lactis, Leuconostoc pseudomesenteroides, Pediococcus pentosaceus, and Tetragenococcus halophilus), one fungus (Aspergillus oryzae), and four yeasts (Zygosaccharomyces rouxii, Saccharomyces cerevisiae, Kluyveromyces marxianus, and Wickerhamomyces anomalus), were used as starter cultures for solid-state fermentation (SSF) of pea protein isolate (PPI). Improved PPI solubility was found to be the main positive effect of SSF. The greatest improvement in protein solubility, nearly a fourfold increase compared to the solubility of unfermented PPI, was achieved in samples fermented with Z. rouxii. Uninoculated “control” PPI samples, which were fermented solely by indigenous microflora, were found to have nearly threefold higher protein solubility than in unfermented PPI, which was greater than in most samples fermented with starter cultures. Two of the tested strains, W. anomalus and T. halophilus, significantly inhibited the beneficial activity of indigenous microflora, leading to unchanged or diminished protein solubilities after fermentation. Changes in protein solubility following SSF correlated with degrees of protein hydrolysis (DH): most samples, which had protein solubility of > 30%, also had DH of > 10%. Additionally, PPI had improved foaming capacity after fermentation with A. oryzae, S. cerevisiae, or L. pseudomesenteroides. Gelation capacity was reduced in all fermented samples; this outcome may be useful in applications where gelation upon heating is not desired. Other functional properties of PPI, such as water and oil holding capacities (WHC and OHC), as well as foam and emulsion stabilities (FS and ES), were either unchanged or reduced after fermentation.