Characterization Of Volatile Compounds Of Chinese Liquors By GC-MS And Sensory Evaluation

The main typical Chinese liquors belonging to different aroma types were measured using Stir Bar Sorptive Extraction-Thermal Desorption System coupled with Gas Chromatography-Mass Spectrometry (GC-MS) and sensory evaluation to provide an insight on the role played by volatile compounds on the different aroma type Chinese liquors.The extraction of volatile compounds by SBSE has been optimized and the optimized procedure was as followed:to a 20 mL glass vial was added 10 mL of diluted liquor sample (10% ethanol content),10 μL of an internal standard solution (2-octanol (400 mg L-1)) and 2 g of sodium chloride. A preconditioned stir bar was introduced to the vial, which was stirred at 750 rpm in a 4 agitation point plate (Meiyingpu Instrument Inc., Shanghai, China). The extraction temperature was set at room temperature (25℃, thermostatted room) with extraction time of 90 min. The optimized TDS procedure was as followed:desorption temperature was programmed from 40 (equilibrium for 1 min) to 260℃ (held at this temperature for 5 min) at 60℃ min-1 under a helium flow (75 ml min-1) and the desorbed analytes were cryofocused in the PTV system with liquid nitrogen at-90℃. Finally, the PTV system was programmed from-90 (equilibrium for 1 min) to 250℃ (held for 1 min) at 12℃ s-1. SBSE coupled with GC-MS was a fast, simple, effective, and reliable method for the aroma characterization of Chinese liquor Calibration curves were achieved for quantification with correlation coefficients ranging from 0.9875 to 0.9996. Limits of detection (LODs) and limits of quantification (LOQs) were obtained ranging from 0.007 to 17.89μg L-1, from 0.02 to 69.6μg L-1, respectively. Repeatability was between 0.2 and 7.0% while intermediate precision was between 0.1 and 7.5%.Afterwards,3 type Chinese liquors were investigated using the SBSE-TDS/GC-MS method. A total of 111 volatile compounds, including 37 esters,10 alcohols,10 acids,6 phenols,6 aldehydes and ketones,8 acetals,5 furans,5 sulfuric compound and 4 pyrazines, were identified and quantified. The obtained results of GC-MS were then subjected to analysis of variance (one-way ANOVA).66 volatile compounds showed significant differences (P< 0.05) among aroma types as a consequence of differences in winemaking processes.50 out of 112 quantified volatile compounds, which had a concentration above the odor threshold (OAV>1) in, at least, one variety, were present. These 50 volatiles were therefore potential contributors to the global aroma of Chinese liquors. Strong-aroma liquors were exhibited the significantly highest OAVs of ethyl hexanoate, ethyl pentanoate, ethyl octanoate, ethyl butanoate, ethyl isovaretate,2-n-butylfuran, dimethyl trisulfide. For light-aroma liquors, the OAVs of ethyl hexanoate, ethyl octanoate, dimethyl trisulfide, dimethyl disulfide, (E,E)-2,4-decadienal,2-n-butylfuran,4-ethyl-2-methoxy phenol and (2E)-2-nonenal appeared the highest. For sauce-aroma liquors, ethyl hexanoate,2-n-butylfuran, ethyl pentanoate, ethyl octanoate, ethyl isovaretate, dimethyl trisulfide, ethyl butanoate, (2E)-2-nonenal, 2-ethyl-3,5-dimethyl pyrazine, ethyl 3-methylpropanoate and 2-methylbutanal had OAVs higher than the other aroma liquors.Nine sensory attributes (sauce, cellar, fen, fruity, floral, sweet, grain, cameral and vinegar) of 3 type Chinese liquors were evaluated by quantitative descriptive sensory analysis. The results showed that 3 type Chinese liquors owned its different aroma profiles. Principal component analysis (PCA) and Agglomerative hierarchical clustering (AHC) can well didtinguished different type Chinese liquors.Partial least squares regression (PLSR) results indicated that ethyl hexanoate and hexanoic acid were significantly and positively associated with cellar aroma and strong-aroma liquors. Fen, sweet and vinegar aroma were strongly linked with light-aroma liquors, with compounds of decanal, heptanal,2-octanone,2-nonanol,3-octanone and 2-undecanone. While sauce-aroma liquors were positively correlated with grain and sauce (significant connotation with ethyl propanoate, ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, hexyl propanoate and ethyl benzeneacetate) aromas. The results also elucidated the correlation between volatile compounds and individual sensory attribute.