Soy sauce is a fermented food with a savory flavor that can enhance the taste of many different dishes. But what exactly makes this complex sauce so tasty? Understanding how foods taste the way they do can help producers tune their manufacturing methods or modify the final product to boost certain flavors. Decoding the flavors of fermented foods like soy sauce is particularly challenging because they arise from complex processes, including the microbial breakdown of proteins and other compounds. Though several compounds in soy sauce are known, no complete profile of its flavor agents has been developed.

Thomas Hofmann, Technical University of Munich, Freising-Weihenstephan, Germany, and colleagues have aimed to carry out a full assessment of taste-active and taste-modulating compounds responsible for the typical taste signature of soy sauce, as well as test the completeness of this profile by using the compounds to recreate the taste of soy sauce. They first tried to recreate soy sauce’s taste with a mixture of compounds known to be involved in its flavor. A panel of taste experts found that this recreated soy sauce was not as salty or as bitter as the authentic product.

The team then searched for other, unknown flavor compounds, hypothesizing that small proteins could be the missing ingredient. The team quantified peptides using ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). They identified 14 umami- (savoriness), kokumi- (richness), and salt-enhancing peptides for the first time, for example, proline-modified dipeptides. Several of the proteins were found to contribute to a salty sensation, which, in soy sauce, had previously been attributed only to table salt and other minerals.

When the peptides were added to the team’s recreated soy sauce, the overall taste intensity was increased and the taste profile matched that of soy sauce much more closely. This work could help producers optimize fermentation conditions to boost desirable compounds and tune the taste of the final product.

• Sensoproteomic Discovery of Taste-Modulating Peptides and Taste Re-engineering of Soy Sauce,
  Manon Jünger, Verena Karolin Mittermeier-Kleßinger, Anastasia Farrenkopf, Andreas Dunkel, Timo Stark, Sonja Fröhlich, Veronika Somoza, Corinna Dawid, Thomas Hofmann,
  J. Agric. Food Chem. 2022.
  https://doi.org/10.1021/acs.jafc.2c01688