Formation of Ethyl Carbamate during the Production Process of Cantonese Soy Sauce

Abstract

The aim of this work was to clarify the formation of ethyl carbamate (EC) and its influence factors throughout the production process of Cantonese soy sauce. The results showed that EC was not detected in the koji-making and early moromi fermentation stages, but started to be generated when pH of the moromi decreased to about 4.9—at the same time, the levels of ethanol, urea and citrulline increased significantly. Most EC was formed during raw soy sauce hot extraction (40.6%) and sterilization (42.9%) stages. The EC content exhibited the highest correlation with ethanol throughout the whole production process (R = 0.97). The simulation soy sauce produced in laboratory led the same conclusion—moreover, the contents of EC, ethanol and citrulline were higher in soy sauce fermented at 30 °C than in soy sauce fermented at 15 °C. Extraction of raw soy sauce by squeezing contributed little to EC formation. Further research showed that citrulline and ethanol led to significant increases in EC levels in raw soy sauce upon heating. These results indicate that ethanol and citrulline are two critical precursors of EC and that EC is mainly formed during the heat treatment stage of soy sauce.

Citrulline Accumulation Mechanism of Pediococcus acidilactici and Weissella confusa in Soy Sauce and the Effects of Phenolic Compound on Citrulline Accumulation

“…Although Saccharomyces cerevisiae can produce citrulline via arginine metabolism, the generation of citrulline is majorly attributed to the metabolism of arginine by malolactic bacteria via the ADI pathway (Fang et al, 2018). In previous work, citrulline content in moromi was found to continuously increase throughout the fermentation period, and it was significantly accumulated when fermented from 20 to 90 days in Cantonese soy sauce (Zhou et al, 2019). In this study, we isolated 34 strains from moromi and determined their arginine utilization ability.…”

“…Citrulline and ethanol are considered to be the major EC precursors in soy sauce ( Matsudo et al, 1993 ; Zhou K. et al, 2017 ; Zhou et al, 2019 ). However, reducing ethanol content may damage the quality of soy sauce, since a certain amount of ethanol has a major contribution to the flavor and spice taste of soy sauce.…”

Evaluation of Nitrite, Ethyl Carbamate, and Biogenic Amines in Four Types of Fermented Vegetables

“…The ethyl carbamate concentration in each sample was measured using a gas chromatography–mass spectrometry (GC–MS) method [ 19 ]. For each analysis, 4 g of sample was homogenized with 4 mL of distilled water and then sonicated for 10 min.…”

Recent progress and advances in soy sauce production technologies: A review

“…Zhang et al (2016) reported that the citrulline content of soy sauce declined from 26.8 to 5.1 mM, and the EC decreased from 97 to 17 µg/kg when B. amyloliquefaciens JY06 was supplemented during the fermentation. However, slight changes in the soy sauce flavor were noticed (Zhou et al, 2019). To determine and screen precursors and their impact on EC formation during soy sauce production, high-performance liquid chromatography with fluorescence detection has been implemented for the quick and efficient quantification of EC, which could help create hazard analysis and critical control points for soy sauce production (Zhou et al, 2017).…”

“…Another concern is the by-products generated during manufacturing, including ethyl carbamate (EC), a Group 2A carcinogen formed by arginine-consuming bacteria in the moromi mash. Efforts have been made to reduce EC accumulation using salt-tolerant strains, but slight changes in the soy sauce flavor have been reported (Zhang et al, 2016;Zhou et al, 2019). Another by-product is soy sauce residue (SSR), with about 4,500,000 tonnes of SSR is generated annually, and it is usually discarded without suitable application although it contains many nutrients such as proteins and oil.…”