Valorisation of soy by-products as substrate for food ingredients containing L. casei through solid state fermentation

Abstract

Okara and soybean extruded-expelled meals (EEM) were used for preparation of ingredients containing probiotics applying a sustainable technology as solid state fermentation. The effect of three factors: particle size of okara or EEM, cheese whey and water content on the growth of L. casei, pH and total titratable acidity was studied. The particle size did not show significant effect, while addition of cheese whey (0.32 g g−1) maximised the cell growth. L. casei grew with the highest rate (μmax = 7.3 ± 0.9 h−1) in the medium containing okara. The slowest rate was observed with EEM (μmax = 1.9 ± 0.3 h−1). The subsequent unit operations applied for stabilising the ingredient reduced the L. casei count 1 and 0.6 log cycles for okara and EEM respectively. The ingredients could be safety stored, at 25 °C, rendering a probiotic count above 106 CFU g−1 at 63 and 42 days of storage for okara and EEM correspondingly.