The soybean, Glycine max, is a versatile legume native to East Asia, where it was first domesticated in China. It has since become a global commodity and the world’s most widely grown legume, valued for its dual composition of high protein and oil. The average soybean seed contains roughly 40% protein and 20% oil, making it a foundational crop for both human consumption and industrial applications. Because of its diverse uses—from livestock feed and vegetable oil to ingredients for various food products—understanding the different varieties is important for consumers and producers alike.
Classification by Color and Consumption
The most immediate way to classify soybeans is by the color of their seed coat, which often dictates their use in direct human consumption. Yellow soybeans are the most common variety globally, forming the basis for the majority of processed soy foods. These beans are used to produce soy milk, which is coagulated to make tofu, and they are also fermented into products like miso and natto; smaller varieties are often preferred for fermentation processes.
A distinct variety is the black soybean, which possesses a dark seed coat and is often utilized in specific East Asian cuisines. These black beans have a milder flavor profile compared to yellow soybeans and are frequently used in fermented black bean sauces or boiled in savory dishes. Green soybeans, commonly known as edamame, are the immature form of any soybean harvested before the pods ripen and dry out. Edamame is typically boiled or steamed in the pod and served as a snack.
Classification by Industrial Application
Beyond direct food consumption, soybeans are classified based on their chemical composition, which determines their suitability for large-scale industrial processing. This classification focuses on the inverse relationship between the two primary seed components: protein and oil. Breeding programs aim to develop varieties that maximize the concentration of one component over the other, as increasing the level of one tends to decrease the level of the other.
Varieties bred for high oil content are favored by the oil crushing industry, which extracts the oil for use in cooking oils, margarines, and various industrial applications. These high-oil varieties can contain up to 22% oil. Conversely, varieties bred for high protein content are prized for the resulting soybean meal, the defatted solid material left after oil extraction. This meal, which can contain protein levels as high as 48%, is the single largest source of protein concentrate used in animal feed, supporting the poultry, swine, and aquaculture industries.
Genetic and Cultivation Types
Soybeans are also categorized by the methods used to cultivate them. The three primary cultivation types are conventional, genetically modified (GM), and organic. Conventional soybeans are grown using traditional breeding methods and farming practices that may include synthetic pesticides and fertilizers. Genetically Modified soybeans, which make up a large percentage of the global crop, are engineered to possess specific traits, most notably tolerance to certain herbicides, such as glyphosate.
This herbicide-tolerant trait allows farmers to apply broad-spectrum weed killers directly to the crops, simplifying weed management and increasing farming efficiency. Organic soybeans must be non-GMO and are grown under strict regulations that prohibit the use of synthetic pesticides, herbicides, and fertilizers. Organic farming relies on natural methods like crop rotation and mechanical cultivation for weed and pest control. Studies have shown that organic soybeans can have a different nutritional profile, containing higher levels of sugars and protein compared to both conventional and GM varieties.