Effect of soybean soaking conditions on sugars content and α-galactosidases activity

Resumo

The effects of the time and temperature of soybean soaking on the changes in sugar content and α-galactosidases activity were evaluated. Soybean soaking was performed at a 1:1.5 (g:g, soybean: deionised water) ratio at 25, 40, 55 or 70 ºC for 0, 1, 2, 3, 4, 5, 6 and 7 h, and the content and profile of sugars and α-galactosidases activity were determined by high performance anion exchange chromatography (HPAEC) and spectrophotometry, respectively. Soybean soaked at 25 or 40 °C did not show significant changes in raffinose and stachyose contents. Soybean soaking for 3 h at 25, 40, 55 or 70 ° C influenced the activity of α-galactosidases, which hydrolysed the oligosaccharides of soaked soybeans at 55 or 70 °C. Soybean soaking at 55 °C for longer than 3 h showed mean reductions of 45% and 25% in raffinose and stachyose contents, respectively. However, soybean soaking at temperatures of 25, 40, 55 or 70 ºC showed no significant changes (p > 0.05) in the sucrose content. Therefore, soybean soaking at 40 or 55 ºC can be used to promote the partial hydrolysis of raffinose and stachyose to galactose and sucrose. Therefore, maceration under these conditions can be used for the development of soy-based foods with reduced levels of oligosaccharides. This strategy may enhance the digestibility of these products, without completely eradicating the prebiotic benefits associated with the remaining oligosaccharides.