Abstract: During storage, milk is prone to different degrees of oxidative degradation of fat with varying storage conditions, which changes the aroma components of milk. In this study, electronic nose based on gas chromatography (GC) and sensory evaluation were used to compare the changes in the composition of volatile flavor compounds and sensory properties of pasteurized whole milk, low-fat milk and skim milk (fat contents of 4, 1.4 and 0 g/100 mL) during storage at different temperatures. The results showed that all three milks maintained good flavor characteristics during storage at 4 ℃. The composition of flavor substances in whole milk was more complex, where 43 volatile compounds were identified, and no obvious stale flavor was perceived. The decreasing order of difficulty of fat oxidation was whole milk > low-fat milk > skim milk. Nonanal, a marker of lipid oxidation, was detected in both skim milk and low-fat milk. Methyl ketones derived from lipid oxidization such as 2-butanone, 2,3-butanedione, 2-hexanone, 2-heptanone and 2-undecanone were detected in skim milk during storage. The results of sensory evaluation were basically consistent with those of electronic nose. The sweetness and milky flavor of whole milk were more prominent, the flavor of low-fat milk was relatively bland, and skim milk tasted slightly bitter after 21 days of storage at 25 ℃. The findings of this study will provide a scientific basis for monitoring the flavor changes of milk products during storage and improving the quality of milk products.

Key words: milk; electronic nose based on gas chromatography; fat oxidation; volatile components; storage

摘要： 牛乳贮藏过程中，脂肪易随贮藏条件变化而发生不同程度的氧化分解，进而改变牛乳香气成分。结合气相型电子鼻检测和感官评价对比脂肪质量浓度分别为4、1.4、0 g/100 mL的巴氏杀菌全脂乳、低脂乳和脱脂乳中挥发性风味化合物组成和感官特性在不同贮藏温度下随贮藏时间的变化。结果表明：上述3 类牛乳产品在4 ℃下保持了良好的风味特征；全脂乳风味物质更为复杂，共鉴定出43 种挥发性化合物，贮藏期未观察到明显的陈腐味；脂肪氧化难易程度表现为全脂乳＞低脂乳＞脱脂乳；在贮藏期，脱脂乳和低脂乳中均检出脂质氧化标志物壬醛，脱脂乳中还检出2-丁酮、2,3-丁二酮、2-己酮、2-庚酮、2-十一烷酮等脂质氧化产物甲基酮类物质；人工感官评价结果与电子鼻检测结果基本一致，全脂乳甜味和乳香味较为突出，低脂乳风味较为寡淡，脱脂乳在25 ℃贮藏21 d产生轻微苦味。本研究为监测牛乳产品贮藏期风味变化及提升牛乳产品品质提供了科学依据。

关键词: 牛乳；气相型电子鼻；脂肪氧化；挥发性成分；贮藏