梨白兰地中乙醇碳同位素分布特征研究

Distribution characteristics of stable carbon isotope of ethanol in pear brandy

利用元素分析-稳定同位素比值质谱仪测定梨白兰地原料的糖中δ13C,发酵后用气相色谱-燃烧-同位素比值质谱法分析乙醇中碳稳定同位素比值(δ13C)。结果显示梨的糖中δ13C值分布在-27‰^-25‰,而发酵后的乙醇δ13C集中在-30‰^-27‰,且糖与乙醇的δ13C具有良好的线性正相关关系(R2=0.98);白兰地精馏过程中乙醇出现反蒸汽压分馏效应,但酒体部分(50%vol^80%vol)δ13C值波动较小,重现性较好,且与发酵醪中的δ13C值较一致。模拟实验表明,乙醇δ13C值与玉米酒精含量和蔗糖含量成正相关关系,发酵前添加蔗糖和玉米酒精均会改变产品中乙醇δ13C值,因此碳稳定同位素技术可作为检测白兰地中C4来源的酒精或发酵前C4植物糖掺假的鉴别手段。

The 13C/12C stable isotope ratio（δ^13C of juice sugar was detected by elementary analyzer-stable isotope ratio mass spectrometers and the δ^13Cof ethanol was measured by gas chromatography combustion isotope ratio mass spectrometry after fermentation.Results showed that the δ^13Cof pear juice sugar ranged from-27‰ to-25‰,with the δ^13Cof ethanol after fermentation ranged from-30‰ to-27‰,and a significant correlation （R2=0.98） between δ^13Cvalues of sugar and ethanol was observed.The inverse vapor pressure isotope effect was observed for the carbon isotopologues of ethanol during distillation process.But the δ^13Cof wine body part （50%vol-80%vol） didn＇t fluctuate greatly,the reproducibility was good and the mean δ^13Cvalue of ethanol in this distillate fraction was consistent with the fermented mash.Simulation test showed that the δ^13Cof ethanol was in positive relation with maize ethanol and sucrose content,and the δ^13Cof ethanol would be changed when sucrose and maize ethanol were added before fermentation.The method can be used for C4 source alcohol or C4 source sugar authentication before fermentation in brandy.