Chemical and Sensory Characteristics of Soy Sauce: A Review

Abstract

Soy sauce is a fermented product, and its flavor is a complex mixture of individual senses which, in combination, create a strong palatable condiment for many Eastern and Western dishes. This Review focuses on our existing knowledge of the chemical compounds present in soy sauce and their potential relevance to the flavor profile. Taste is dominated by umami and salty sensations. Free amino acids, nucleotides, and small peptides are among the most important taste-active compounds. Aroma is characterized by caramel-like, floral, smoky, malty, and cooked potato-like odors. Aroma-active volatiles are chemically diverse including acids, alcohols, aldehydes, esters, furanones, pyrazines, and S-compounds. The origin of all compounds relates to both the raw ingredients and starter cultures used as well as the parameters applied during production. We are only just starting to help develop innovative studies where we can combine different analytical platforms and chemometric analysis to link flavor attributes to chemical composition.

Keywords: Maillard reactions; aroma; fermented; gas chromatography−mass spectrometry (GC-MS); liquid chromatography−mass spectrometry (LC-MS); soy sauce; taste.

Figure 1

Flowcharts of key stages in production of traditionally fermented soy sauce (A) with variations [J, Japanese-type; C, Chinese-type; T, Tamari] and acid-hydrolyzed soy sauce (B).

Figure 2

GC-MS volatile profiles of two soy sauce samples extracted by SBSE: traditionally fermented (A) and acid-hydrolyzed soy sauce (B). The untargeted volatile profiles shows quantitative and qualitative differences (unpublished data from the authors). The column used was a Zebron ZB-5MSplus with dimensions 30 m × 0.25 mm × 1.00 μm (Phenomenex).

Figure 3

Proposed flavor wheel of soy sauce, constructed on the basis of taste and aroma attributes described in literature (data shown in Tables 2 and 3). For each attribute, one typical example of a sensory-relevant molecule is also presented. More examples of taste- and aroma-active molecules described in soy sauce can also be found in Tables 2 and 3, respectively.

Figure 4

Analytical approaches commonly used to characterize non-volatile and volatile compounds in metabolomics applications. Different techniques can be selected for the various extraction, separation, and detection steps, as well as to eventually link specific compounds to flavor characteristics.