Sufu is a traditional condiment in Chinese cuisine, often added to dishes like stir-fried vegetables or a rice porridge called congee. To make sufu, tofu is fermented with a fungus and then brined with salt and alcohol, producing a white, cheese-like product with a creamy texture and a rich, floral flavor. Researchers have been studying the compounds that make up sufu’s unique flavor for decades. Now, inspired by a similar study on fermented fish sauce, a group at Shanghai Jiao Tong University and the Chinese University of Hong Kong has identified peptides in sufu that could enhance salty flavors when added to other foods (J. Agric. Food Chem. 2021, DOI: 10.1021/acs.jafc.1c03431).
The researchers ground up freeze-dried samples of store-bought sufu, filtered out the fat, and used a combination of chromatography and mass spectrometry to isolate 11 peptides containing aromatic amino acids such as tyrosine and phenylalanine, which are suspected of being mainly responsible for sufu’s flavor. The researchers then exposed taste bud cells cultivated from rats to the peptides and measured intracellular changes in calcium levels that indicated a reaction to salty stimuli.
Next, a trained team of nose-clipped sensory panelists sipped peptide-spiked cups of lightly salted water and evaluated the taste. Two of the peptides increased the perceived saltiness by about 25%. Although significant, the increase is not as dramatic as that of artificial sweetener peptides such as aspartame, which tastes 200 times as sweet as sucrose. Yan Ping “Catherine” Chen, lead author of the study, hopes that future research can identify sufu peptides that can enhance the perception of saltiness by at least 50% or find other flavor compounds from sufu that may be able to replace salt altogether.