Processed soybean remains from ancient Korean sites: archaeobotanical insights into legume storage and culinary practices

This article investigates amorphous charcoal lumps dating to approximately AD 200–400 that were recovered from the Yongsan-dong site on the southern Korean Peninsula. Microscopic examination and stable isotope (δ¹³C and δ¹⁵N) analyses support the identification of the lumps as crushed soybean remains (Glycine max (L.) Merr.). The lumps consist exclusively of soybeans, with no evidence of other plant materials. Experimental carbonization of soybeans and soybean-based food products under controlled conditions indicates that the remains were shaped into a dough-like form before charring. The closest modern analogue is meju, a traditional fermented soybean product central to Korean cuisine, although fermentation cannot be directly demonstrated in the charred remains. Extending the investigation to similar remains from four additional archaeological sites on the southern Korean Peninsula corroborates this interpretation and further suggests that the practice of processing soybeans into lumps—an intermediate step in the production of fermented soybean paste—existed as early as AD 200. Drawing on historical and ethnographic information, this study discusses the culinary and social significance of these materials, particularly in relation to food storage, flavor development, and culinary practices.