BLACK soya beans, popularly known in Japan as ‘kuromame’, are fascinating legumes recognised for their glossy black colour, sweet-nutty flavour, and high nutritional value, earning them the reputation of a superfood. While the pale-yellow soya bean dominates the global oil and feed industry, black soya beans belong to a more elite category, valued not merely for calories and protein, but also for their abundance of antioxidants, bioactive compounds and culinary versatility.
Black soya bean (Glycine max), like yellow soya bean, is an annual, erect, herbaceous legume with trifoliate leaves, purple flowers, and 2–4 seeded pods. The main distinction lies in the seed coat colour: black soya bean produces glossy black seeds that are rich in anthocyanins and antioxidants, whereas yellow soya bean has pale-yellow seeds with comparatively lower antioxidant content. Cotyledon colour, growth duration of about 80–100 days, and cultivation requirements are similar, though black soya bean tends to be slightly more tolerant of marginal soils. Unlike yellow soya bean, which is mainly grown for oil and feed, black soya bean is valued for human consumption due to its superior nutritional and functional qualities.
In Bangladesh, soya bean is already a recognised crop, cultivated primarily in coastal regions such as greater Noakhali, Bhola, Tangail and Barishal, mainly for oil and poultry feed. Yet the black variety remains largely unfamiliar to most farmers and consumers. With global recognition of black soya bean as a functional food, interest is growing among researchers, agribusiness entrepreneurs and policymakers in introducing it to Bangladesh on a larger scale. If properly developed, black soya bean could enrich local diets, provide farmers with a profitable cash crop, and open new export opportunities in East Asian markets, where ‘kuromame’ is in high demand.
Soya bean cultivation traces back to ancient China, where it was revered as one of the ‘five sacred grains.’ Over time, soya bean spread to Korea and Japan, where different varieties, including the black type, were domesticated. Black soya beans, in particular, held spiritual and medicinal significance. In traditional Chinese medicine, they were used to ‘tonify the kidneys,’ improve circulation, and balance energy. In Japan, ‘kuromame’ became an integral part of cultural celebrations. During the New Year festival, stewed black soya beans are served as part of ‘osechi ryori’, symbolising strength, health, and diligence. Eating them is believed to bring good fortune in the year ahead. In Korea, black soya beans are used in dishes such as ‘kongjaban’ (soy sauce–glazed beans), while in Vietnam and China, they are sometimes brewed into medicinal teas.
In the western world, black soya beans only gained popularity in recent decades, when health-conscious consumers began exploring plant-based protein options. Unlike yellow soya bean, largely crushed into oil and feed, black soya beans entered the market as a whole food. Today, they are marketed as gluten-free, low-carbohydrate, high-protein beans, suitable for diabetics, vegetarians and people seeking functional foods. Bangladesh can learn from these experiences: Japan shows how black soya bean can be integrated into cultural cuisine; Korea demonstrates its role in everyday side dishes; and the west highlights its potential as a marketed health product. Together, these lessons can guide Bangladesh’s strategy to position black soya bean as both a local food innovation and an export commodity.
Black soya beans are unique because they combine the macronutrient strength of legumes with the antioxidant power of fruits. On average, per 100 grams of dry seeds, they contain 35–40 grams of protein, 18–20 grams of fat (mostly unsaturated), 30–35 grams of low-glycaemic carbohydrates and 15–20 grams of dietary fibre, providing 400–450 kcal. They are also rich in essential minerals such as iron, calcium, magnesium, phosphorus and zinc, and contain vitamins including B1, B2 and folate. In addition, they provide bioactive compounds such as isoflavones, anthocyanins and flavonoids, which act as natural protectors against chronic diseases. This dense composition makes black soya bean superior to many common pulses such as lentil, chickpea, or mung bean. While these pulses are good sources of protein, they lack the combination of isoflavones and anthocyanins that black soya bean provides.
Anthocyanins in black soya bean are the same compounds that give blueberries their colour. These antioxidants neutralise free radicals, slowing cell damage and ageing, and regular intake has been linked to reduced risks of cancer, neurodegenerative disorders and cardiovascular disease. Black soya bean’s low glycaemic index ensures that it does not spike blood sugar levels after meals, while isoflavones improve insulin sensitivity and dietary fibre slows glucose absorption, making it ideal for Bangladesh, where diabetes prevalence is increasing. The unsaturated fats lower low-density lipoprotein cholesterol, while anthocyanins prevent arterial plaque build-up, together reducing risks of heart attack and stroke. Calcium, magnesium and phosphorus contribute directly to bone density, while isoflavones mimic oestrogen, helping postmenopausal women maintain bone health and reduce osteoporosis risk. Isoflavones also help balance hormones, reducing menopausal symptoms in women and offering protective effects against prostate cancer in men. Additionally, fibre improves digestion, and bioactive compounds strengthen the immune system. Emerging research suggests that soy isoflavones may also improve gut microbiota balance, enhancing overall digestive and immune health.
Yellow soya bean is mostly used for oil extraction and livestock feed. Although high in protein, it contains less anthocyanin and fewer bioactive compounds. Black soya bean, in contrast, is grown primarily for direct human consumption. It is richer in antioxidants, more suitable for functional foods, and considered premium in global markets. Thus, while Bangladesh grows yellow soya bean for industry, black soya bean could target health-conscious consumers and international export markets.
At the agronomy department, Gazipur Agricultural University, in collaboration with Grameen Euglena Ltd, initial trials have tested black soya bean under local conditions. Early findings indicate good germination rates under Bangladesh’s subtropical climate, satisfactory growth and yields in research fields, strong nodulation indicating nitrogen-fixation ability, and promising stress, pest, and disease tolerance. However, these trials are still limited in scope, and multi-location trials are essential for black soya bean to become a mainstream crop. Potential regions for cultivation include the southern coast (Noakhali, Bhola, Barishal), already favourable for yellow soya bean; the Sylhet hill tracts, with acidic soils suitable for legumes; the Madhupur tract, offering moderately high land ideal for crop diversification; the drought-prone Barind tract, which could be tested for short-duration crops; and coastal chars, where black soya bean could provide income for marginal farmers in newly accreted lands. Such studies would clarify long-term adaptability, disease resistance and yield potential across Bangladesh’s varied agro-ecological zones.
Yellow soya bean dominates the domestic market for fish and feed ingredients, but black soya bean opens new niches. It can be processed into roasted snacks, providing crunchy, protein-rich treats for urban consumers and into soy flour for breads, noodles and biscuits to enrich protein content. It can also be made into soy milk and tofu, serving as dairy alternatives for lactose-intolerant consumers. Specialty drinks such as soy tea and other antioxidant-rich beverages are gaining popularity in Asia, while nutraceuticals and dietary supplements derived from black soya bean compounds could cater to health-conscious consumers. Urban areas such as Dhaka, Chattogram and Sylhet, with rising demand for healthy and functional foods, would be ideal entry markets. Internationally, Japan, Korea and China already maintain strong demand for black soya beans. Bangladesh could target these markets provided it ensures consistent quality, reliable supply chains and certification standards. Given Bangladesh’s proximity to East Asia, black soya bean could emerge as a niche export alongside tea, shrimp and jute products.
Despite the potential, several challenges must be addressed. Bangladesh currently does not have locally adapted black soya bean varieties and no large-scale seed production or distribution system exists. Processing infrastructure is limited, as specialised facilities are needed to produce tofu, soy milk, and nutraceutical products. Consumer awareness remains low, as most Bangladeshis have never heard of black soya bean. Farmers may be reluctant to adopt new crops without assured markets and fair prices.
To overcome these barriers, a structured roadmap is needed. This includes expanding research through multi-location trials in coastal, hill and drought-prone regions, developing high-yielding and climate-resilient varieties, establishing certified seed production and distribution systems, providing farmer incentives such as price support, training and crop insurance, encouraging private investment in processing units, running consumer awareness campaigns to highlight health benefits, obtaining export certifications and building trade relations with Japan and Korea, including black soya bean in agricultural diversification programmes and fostering public–private partnerships connecting universities, agribusinesses and farmer cooperatives.
Bangladesh faces rising sea levels, salinity intrusion and erratic rainfall, making climate-smart crops increasingly important. Black soya bean could serve as a climate-resilient crop, tolerating moderately saline soils, fixing nitrogen to improve soil fertility and growing as a short-duration crop between rice seasons. It also provides high-protein food security during times of climate stress, aligning with Bangladesh’s goals of climate adaptation and nutritional security.
Black soya beans are more than just a crop, they are a pathway to healthier diets, profitable farming and new export opportunities for Bangladesh. Their rich antioxidants, high protein and functional benefits make them a superfood with global appeal. With focused research, farmer support, processing infrastructure and government policy, Bangladesh can transform black soya bean from a niche crop into a mainstream agricultural and export success, boosting nutrition, income and climate-resilient farming.
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Dr MA Mannan is a professor and soya bean researcher at the agronomy department in Gazipur Agricultural University.