Soybeans are one of the five major grains, known for its diverse uses and as a staple that shapes East Asian food culture. In this paper, I will argue that soybeans originated in the Korean Peninsula, whose usage there can be verified from multiple sources. The Korean Peninsula provided an optimal natural selection environment for the cultivation of primitive soybeans, whose origins date back to about 3000 BCE. These soybeans differed in size, shape, and mass from the primitive soybeans of the Central Plains. Furthermore, various processed foods made from soybeans—such as soy sauce, tofu, soybean oil, and bean sprouts—have influenced the taste preferences of East Asians and elevated the status of soybeans.

Moreover, the development of processing techniques has led to the development of the flour industry and introduced flour-based foods and soybean oil, bringing changes to dietary habits. The byproducts from this processing have been utilized as livestock feed, fertilizers, and fuel, and were also used as emergency crops during disasters. Additionally, the intercropping and root cultivation of soybeans has increased land utilization, making them an indispensable presence in the daily lives of farmers.

This paper is divided into three main parts. The first part presents the idea that "rongshu" from the Northeast during the Spring and Autumn period underwent domestication and evolution starting from the Korean Peninsula and then spread throughout the world. This led to the possibility of producing fermented soybean products like soy sauce, which would have been impossible with wild soybeans alone. This "rongshu" was a precursor to the Goryeo bean (高麗豆),  which has been discovered to have been cultivated earlier in various primitive forms in the Korean Peninsula. Therefore, it is reasonable to conclude that the Korean Peninsula was the origin of cultivated soybeans, with its roots in the "meju" beans of Korea.

The second part of my paper examines the processing methods for soybeans and related foods. The critical transformation of soybeans from a staple to a side dish was made possible by the development of processing tools. The progression from mortars to grinding stones, watermills, and stone rollers improved milling productivity, leading to the flourishing of the milling industry. However, conflicts soon arose between farmers and millers over the access to water that powered the watermills, requiring the intervention of the imperial court. This rapid development of production methods brought about changes in agricultural management during the Middle Ages, steering dietary habits toward a focus on flour-based foods.

The third part of my paper will consider the emergence of soybean and adzuki beans[小豆] that were processed for food in the Korean Peninsula. The conditions that allowed for the early appearance of sauces and meju (豉) alongside Goryeo beans in the Korean Peninsula included high-quality ceramics and fermentation techniques (such as fish sauce and compost production). However, the biggest challenge in researching ancient soybean processed foods in the Korean Peninsula has been the lack of records, which has necessitated heavy reliance on Chinese sources. Fortunately, the records of doenjang(末醬) excavated from the Goryeo seabed and ancient Japanese soy sauce and meju provided insight into the spread of these processed foods. Additionally, abundant materials on soybeans and their processed products in Joseon period allowed for inferences about earlier periods.

The reason for reexamining the history of soybeans in this book is not only due to the origins of the bean itself but also because soybeans are gaining attention as a future health food. Processed products made from soybeans include a variety of items such as bean rice, soybean paste, meju (豉), tofu, bean sprouts (豆芽), soybean oil, soy milk, bean cake (豆餠), bean flour (豆粉), cheongkukjang (淸麴醬: fermented soybeans), and industrial raw materials, among many others. The by-products are increasingly being used as livestock feed and fertilizers. Soybeans are rich in plant-based protein, making them a focus of a healthy diet for modern consumers. Therefore, interest in soybeans is natural, and a new examination of their origins, dissemination, and uses is needed.

As outlined above, soybeans and adzuki beans, along with their related products, have become widely popular and diverse over time in the Korean Peninsula, and are now firmly established as essential foods for Koreans. This can be attributed to the ecological conditions and historical identity that soybeans possess.

- Author: Choi, Dukkyung (Department of History, Pusan National University)