Nutritional characteristics of soybean seed flour after processing with sodium bicarbonate or trona

Abstract

Flours were prepared from soybean seeds which had been blanched in water, sodium bicarbonate (0.5%) or trona (sodium sesquicarbonate; 0.5% or 1.0%), with or without prior soaking for 24h in same solutions. All treatments removed significant proportions of the undesirable oligosaccharides raffinose and stachyose, and resulted in flours of high protein digestibility (as measured in vitro). Soaking and blanching in trona resulted in a 6-7% decrease in protein content in comparison with blanching in water alone, but this was partially offset by increases in protein digestibility and available lysine. The use of 1% trona caused some darkening of the soybean seed flour. Trona is an inexpensive and familiar processing aid, readily available to rural and urban households in Nigeria. Its use in moderate quantities may be safely recommended to reduce soaking and cooking time in the production of nutritionally and organoleptically acceptable soybean products, thereby encouraging increased consumption of this valuabl...