Soaking of soybean meal: evaluation of physicochemical properties and kinetic studies

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Soaking is an important pre-requisite for soybean meal processing including fermentation. Soybean meal is soaked at 20, 30, 40, 50 and 60 °C for 10 h in order to investigate the effect of soaking on moisture gain and nutritional properties including crude protein content, carbohydrate content and antioxidant activity. The properties of the soaking water (pH, turbidity and colour parameters using L*a*b* scale) are also investigated. For soybean meal, the effective moisture diffusivity varied from 1.14 × 10 −11 to 2.07 × 10 −11 m 2 s −1 and the water absorption data fitted well with Peleg and Abu-Ghannam models. The total phenolic content and DPPH radical-scavenging activity are found to be significantly (p < 0.05) affected by soaking time and temperature and a maximum decrease of 90% and 20% are observed, respectively. For phenolic compounds, the effective diffusivity varied from 0.9 × 10 −11 to 1.19 × 10 −11 m 2 s −1 and the data fitted with the second order kinetic model. Crude protein and carbohydrate content decrease by 7% and 4%, respectively and are significantly (p < 0.05) affected by soaking time only. The pH of the soaking water reduces to mildly acidic (6–6.5), a* and b* values increase but L* value decreases. Both time and temperature are found to have significant (p < 0.05) effects on all tested properties of soaking water. The best conditions for soybean meal soaking are found to be 50 °C and 1 h within the range used. At these conditions, the desirable moisture content (45–55%) can be achieved in a reasonable time and with minimum loss of nutrients.status: publishe