Stereoselective Behavior of the Fungicide Benalaxyl During Grape Growth and the Wine-Making Process

Benalaxyl is widely applied as a fungicide during grape planting processing. In this experiment, the stereoselective behavior of benalaxyl was studied during the grape growth and wine-making process. A simple method based on high-performance liquid chromatography (HPLC) equipped with a chiral column and UV detector was established to separate and determine the enantiomers of benalaxyl. Stereoselective degradation of the two enantiomers of benalaxyl was found in grapes. The degradation of both enantiomers followed pseudofirst-order kinetics, and the degradation rate of R-(-)-benalaxyl was faster than S-(+)-benalaxyl. The half-life of R-(-)-benalaxyl was 27 h, while the half-life of S-(+)-benalaxyl was 31 h. The enantiomer fraction value decreased from 0.50 to 0.34 and finally only S-(+)-benalaxyl could be detected. In the fermentation process, both enantiomers of benalaxyl were hardly degraded, and no configuration interconversion was observed. Meanwhile, both enantiomers of benalaxyl showed little influence on the growth of the yeast, consumption of carbon sources, or production of alcohol. The result of this study might provide more sufficient data for the evaluation of food safety and potential risk. Chirality 28:394-398, 2016. © 2016 Wiley Periodicals, Inc.