A Study Of Detection And Formation Of GSM In Chinese Liquor

Geosimn (GSM) is found to be responsible for the bran off-flavor in Chinese liquor. The bran off-flavor, one of the most common off-flavors in Chinese liquor, is highly detrimental to the aromatic quality of Chinese liquor, especially light-aroma type. In this paper, methods were developed to determination of GSM in Chinese liquor, Daqu and fermented grains. During the processes of Daqu making and liquor brewing, the evolvement of GSM is analyzed extensively. On the basis of that, the origin of the off-flavor is interpreted in order to control it effectively in Chinese liquor. The main research contents and results were as follows:A fast and simple method for the determination of GSM in Chinese liquor by headspace soild phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was established. Six extraction parameters including different types of extraction fibers, alcohol strength, volume of NaCl addition, pH, extraction temperature and extraction time were optimized. According to the results of the optimization experiments, the following conclusion can be drawn:A total of8mL of sample (5%vol alcohol strength, pH=8) with3g NaCl was efficiently equilibrated for10min and extracted for60min under50℃with75μm CAR/PDMS SPME fiber. Under optimal conditions, the proposed method affords wide range of linearity, high linear regression coefficients (R2>0.999), less than10.99%repeatability of RSD, and limits of detection (LODs)9.12ng/L. The proposed method has satisfactory accuracy, with recoveries of84.1to105.6%. This method was successfully applied for the analysis of GSM in Chinese liquor samples.A fast and simple method for the simultaneous determination of GSM in Daqu and fermented grains by gas chromatography-mass spectrometry (GC-MS) was established. The analytes were extracted by atmospheric distillation with ethanol solution, and extracted then by headspace solid-phase microextraction (HS-SPME) using75μm CAR/PDMS fiber. After concentration, the sample was analyzed by GC-MS and quantified by the external standard method. The linear range was from25ng/L to2000ng/L for GSM, the correlation coefficients (R2) of the calibration curves were above0.99. The recoveries ranged from89.4%to110.3%with the RSDs between6.09%-11.25%. The LODs was10.65ng/L.A quantitatively study was performed to investigate the origin of GSM during the process of Daqu making. The concentrations of GSM in Daqu were measured during the Daqu-making process. GSM was not detected in Daqu adobe made from crushed wheat and water. From day0to day4of culture in house, the content of GSM found in Daqu was increased, Then it decreased to1.52μg/kg dry Daqu at day13. After that, GSM concentration of Daqu continued to grow to5.23μg/kg untill the end of inhouse Daqu cultivation. GSM concentrations in fermented sorghums at different fermentation periods were measured. At the beginning of the fermentation process, GSM concentration increased to1.90μg/kg dry fermented sorghums until day12, but decreased to1.42μg/kg dry fermented sorghums from day12to day24. It suggests that microorganisms that develop in Daqu are responsible for the presence of GSM in Chinese liquor.