采用顶空固相微萃取-全二维气相色谱-飞行时间质谱(headspace solid phase microextraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry,HS-SPME-GC×GC-TOFMS)技术对全脂牛乳(whole milk,WM)、低脂牛乳(low-fat milk,LFM)和脱脂牛乳(non-fat milk,NFM)3 种牛乳样品进行挥发性化合物分析,结果表明:共检测到49 种挥发性化合物,其中2-壬酮、2-十一酮等奇数碳链的甲基酮构成WM的主要风味化合物;偏最小二乘法判别分析表明,其模型可以很好地区分3 种牛乳样品,并且有较好的方差和交叉验证预测能力;通过变量投影重要性＞1、P≤0.05且含量≥1%筛选出9 种化合物,被认定为关键香气差异化合物,这些化合物可能是导致3 种牛乳风味不同的主要因素;聚类热图结果表明,NFM因异味化合物(如十六醛)的存在可能导致不良感官表现,而WM和LFM存在更多的香气化合物,令其在感官方面具有饱满丰富的香气.本研究建立了HS-SPME-GC×GC-TOFMS分析牛乳的研究方法,为乳制品风味改进和乳制香精调配提供了理论指导.
Analysis of Volatile Compounds in Three Milks with Different Fat Contents by GC×GC-TOFMS
In this study,headspace solid phase microextraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry(HS-SPME-GC×GC-TOFMS)was used to analyze the volatile compounds in whole(WM),low-fat milk(LFM)and non-fat milk(NFM).Altogether 49 volatile compounds were detected,among which methyl ketones with odd-numbered carbon chain lengths such as 2-nonanone and 2-undecanone constituted the main flavor compounds of WM.Using partial least squares discriminant analysis(PLS-DA),a model which could well differentiate among the 3 milks was developed and it was found to have good variance and cross-validation predictive ability.Nine differential key aroma compounds were identified using variable importance in the projection(VIP)>1,P≤0.05 and their contents≥1%as criteria,which may be the main factors contributing to the differences in flavor profiles among the 3 milks.The heatmap from clustering analysis indicated that NFM had poor sensory performance due to the presence of off-flavor compounds(e.g.,hexadecanal),whereas WM and LFM contained more aroma compounds,having a full and rich sensory aroma profile.The HS-SPME-GC×GC-TOFMS method can provide theoretical guidance for dairy flavor improvement and dairy flavoring formulation.
non-fat milkflavorheadspace solid phase microextraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometrypartial least squares discriminant analysis
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