Stereoselective Behavior of the Chiral Herbicides Diclofop‐Methyl and Diclofop During the Soy Sauce Brewing Process

Abstract

Chiral pesticides are now receiving more and more attention in the food-making process. This experiment studied the enantioselective behavior of diclofop-methyl (DM) and its main metabolite, diclofop (DC), during the soy sauce brewing process. Two kinds of commonly used strains, Aspergillus oryzae and Saccharomyces rouxii, were investigated. However, they showed a different degradation ability to the enantiomers of DM and DC. It was observed that (-)-(S)-DM was degraded much faster than (+)-(R)-DM by Saccharomyces rouxii, while no stereoselective degradation was found by Aspergillus oryzae. DC represented a relatively long residue period in this fermentation process and both strains showed a weak degradation ability to DC, especially Saccharomyces rouxii. There was little DC detected in the final product, while most of the DC residues persisted in the lees, which were usually used as animal feeds or discarded into the environment directly as waste. Therefore, more attention should be paid to the soy sauce brewing process concerning pesticide residues both in the final product and byproducts.

Enantioselective Behaviors of Chiral Pesticides and Enantiomeric Signatures in Foods and the Environment

“…During soy sauce brewing processes, the degradation of S-(−)-diclofop-methyl was faster than R-(+)-diclofop-methyl by Saccharomyces rouxii, while no stereoselectivity was observed by Aspergillus oryzae. 152 Currently, the effects of microorganisms or enzymes isolated from agricultural products or processed foods on the enantioselective degradation of chiral pesticides need further research.…”

“…For instance, soy sauce is a kind of traditional fermented seasoning used in Asian countries, which is produced by fermentation of a mixture of soybean, wheat, and salt by certain strains of koji mold. During soy sauce brewing processes, the degradation of S -(−)-diclofop-methyl was faster than R -(+)-diclofop-methyl by Saccharomyces rouxii , while no stereoselectivity was observed by Aspergillus oryzae . Currently, the effects of microorganisms or enzymes isolated from agricultural products or processed foods on the enantioselective degradation of chiral pesticides need further research.…”