ABSTRACT
Vigna umbellata (Thunb.) Ohwi and Ohashi, previously known as Phaseoluscalcaratus, is a warm-season legume, commonly called a rice bean and it is a mixed crop with maize, sorghum and cow peas. It is grown by subsistence farmers on a very limited scale and most of the produce is consumed at home, although it is mainly cultivated in India, Nepal, China and Bangladesh. Rice beans are attracting attention worldwide owing to their high yielding ability, resistance to viral, fungal and bacterial diseases, adaptability to grow in less-fertile lands, simple domestic processing, and good nutritional potential, which helps to make it an affordable substitute for conventional pulses. It is mainly cultivated for human consumption and often for fodder and green manure. Rice bean seeds are slender to oblong in shape, round-ended with shiny smooth surface, 6–8mm in length, 3–5mm broad, and 3–4mm in thickness. The dry seeds are highly nutritious, containing 17.26–21.42% crude protein with excellent protein digestibility (59–93%) and all essential amino acids especially (methionine, tryptophan, lysine, tyrosine, and valine), minerals, vitamins, and a relatively high proportion of healthy, unsaturated fatty acids, which all help to make it a nutritious health package. The low glycemic index (GI) of rice bean starch opens its avenue to be suitable for diabetics as well. However, presence of some antinutritional factors such as polyphenols, tannins, phytic acid, and enzyme inhibitors limit their convention, but household processing treatments such as sprouting, pressure cooking, fermentation, microwave cooking, de-hulling, roasting, extrusion, and flaking and roasting improve their nutritional adequacy and safety. New rice bean products with higher nutritional quality, safety, and stability to curb malnutriton can be obtained by applying these techniques alone or in combination. Therefore, it can be concluded that food and nutritional security from rice beans can only be attained if adequate postharvest management, processing, and value additions are followed.
