Physical changes in Isolated Soy Protein under Solid-State Fermentation by Different Microorganisms Sudarma Dita Wijayanti1*, Ainur Rohma Zahra1 , Azizah Nuristia Widyastuti1, An-nisa Aulia Wismada1, Kamon Yakul2
1Department of Food Science and Biotechnology, Faculty of Agricultural Technology, Universitas Brawijaya, Malang 65145, Indonesia
2Division of Biotechnology, Faculty of Agro-Industry, Chiang Mai University, Chiang Mai 50100, Thailand
Email: dee_ta2002[at]ub.ac.id
Abstract
Soy protein isolate (SPI) is a soy-derived product with high protein content, good amino acid profile, and bioactive components that are beneficial to health. To optimize its functional potential in food, SPI can be fermented with various types of microbes. This study aimed to compare the effects of three microbes - Aspergillus oryzae, Bacillus subtilis, and Lactobacillus plantarum - on the physical properties of SPI under solid-state fermentation at seven different time points (0, 3, 6, 12, 24, 36, and 48 hours).The brightness value (L*) of SPI fermented by all microorganisms decreased over time. The reduction in brightness was likely influenced by incubation time, drying temperature, and the high protein content which promoted non-enzymatic browning reactions, resulting in darker color. The redness value (a*) of fermented SPI increased, due to the presence of pulcherrimin, a reddish pigment produced by the bacteria. Meanwhile the yellowness (b*) value of SPI fermented by the three microbes decreased with increasing fermentation time. Functional properties such emulsion capacity and stability were also affected by fermentation especially after 24 hours of fermentation
