Rice bean

Rice bean is a twining or semi-erect annual vine in the same genus as mung bean and adzuki bean. It bears yellow flowers and slender pods 5 to 12 cm long, each holding several small, oblong seeds. Seeds vary in colour from cream and yellow to red, brown and mottled, and are about the size of a grain of rice, hence the name. The plant is also grown for fodder and as a green manure. Cooked rice beans are mild and slightly sweet, with a texture similar to other small pulses, and they are used whole or as a split dal.

Rice bean is thought to have been domesticated in Southeast Asia, and its wild relatives are found across a region ranging from Southeast Asia to Southern China. It was spread across the hills and mountains of South Asia, where it is widely grown, including northeast India, Nepal and Bhutan, and in parts of Southeast Asia, southern China and Madagascar. The plant tolerates poor soils, heat, humidity and moderate drought, can be grown in marginal hill terrain and is often intercropped with maize or millet.

Rice bean has been cultivated as a minor crop for generations among hill farming communities, where it provides both food and fodder from the same field. In Nepal, India's northeastern states and parts of Southeast Asia, it is eaten as a dal or soup, added to stews with vegetables or ground into flour. It has remained a crop of subsistence farmers and is rarely grown on a commercial scale or traded widely, which is why it is considered an underutilized crop.

In recent years, agricultural researchers and some nutrition programmes have studied rice bean as a candidate for diversifying diets and farming systems, because of its adaptation to poor conditions and its protein content. Interest comes with caveats: seeds contain anti-nutritional factors that require proper soaking and cooking, and breeding for uniform yields is still limited.

Rice beans are soaked and boiled until soft and eaten as dal, soup or stew with rice and vegetables. In parts of Nepal and northeast India, they are cooked with greens, spices and fermented foods. They can be ground into flour for flatbreads and fritters, sprouted for salads, or boiled and mashed for spreads. Young pods and leaves are sometimes eaten as vegetables, and the whole plant is used as animal fodder and as a green manure to enrich soil.

Rice beans are a source of plant protein, complex carbohydrates, fibre and minerals including iron, zinc and potassium, based on analyses of the seed in agricultural studies. Values vary between varieties and growing conditions, so nutrient figures are approximate. As with other pulses, soaking and thorough cooking reduce antinutrients such as phytic acid and trypsin inhibitors and improve digestibility. They are a useful pulse for diversifying legume intake, as one component of a varied diet.