Research Progress on Soy Food Flavor

The flavor profile of soybean-based foods was a complex system shaped by diverse volatile compounds generated during growth and processing. To date, more than 300 kinds of volatile flavor components have been identified in non-fermented products such as soybeans, soymilk, and soybean proteins. And more than 200 kinds of volatile flavor components have been identified in fermented soybean foods such as fermented black beans and soybean paste. These components include esters, aldehydes, alcohols, ketones, acids, furans, pyrazines, alkanes, sulfur compounds, and etc. Flavor formation in non-fermented soybean products primarily originated from the enzymatic oxidation of polyunsaturated fatty acids (e.g., linoleic and linolenic acids) naturally present in soybeans. This process was catalyzed by lipoxygenase and fatty acid hydroperoxide lyase during processing. The flavor of fermented soybean foods, on the other hand, originated from the complex enzyme systems released during the microbial fermentation process, which metabolized some of the inherent flavor substances in the raw materials. Meanwhile, proteins, fats, carbohydrates, and etc., were decomposed into complex flavor precursors such as peptides, amino acids, fatty acids, and sugars. Subsequently, during the post-fermentation period, a variety of flavors were formed through complex fermentation metabolism and biochemical reactions. Consequently, even within the same category of soybean foods, flavor profiles might exhibit significant variations due to differences in raw materials and processing conditions that regulated oxidation and other biochemical pathways. The characteristic flavors and formation mechanisms of three representative soybean foods: soymilk tofu, Yangjiang Douchi (fermented black beans), and plant-based fermented soybean milk were introduced. The formation mechanism of the flavor of soybean foods was complex. When developing soybean foods, specific and targeted research on the raw materials and processing objectives was required, and it was impossible to generalize.