基于感官评价及GC-MS结合OPLS-DA分析热杀菌对蟠桃汁呈香品质的影响

【目的】 通过解析热杀菌对蟠桃汁呈香物质的影响,结合多元统计模型探究热杀菌过程中蟠桃汁风味品质劣变主要靶点因素,为高品质蟠桃汁风味品质的调控提供理论基础。【方法】 以新疆4种主要的蟠桃品种（‘早露蟠’（ZLP）、‘早蟠’（ZP）、‘瑞蟠1号’（RP1）、‘瑞蟠18号’（RP18））为试材制备果汁样本,在85℃条件下加热处理30 min。利用电子鼻、描述性感官评价及GC-MS分析分别对其热杀菌前后样本的电子鼻响应值、感官特性及香气组成进行分析,在此基础上结合正交偏最小二乘法判别分析（OPLS-DA）模型中VIP值筛选蟠桃汁热杀菌前后标志性差异物。【结果】 描述性感官评价及电子鼻结果表明,4个品种蟠桃鲜汁香气虽存在差异但均呈现较高的清香、桃香、花香及果香,而热杀菌对蟠桃汁香气品质的影响极大,主要表现为清香显著下降,同时甜香、异味及蒸煮味突显。蟠桃汁的香气组成主要为酯类、内酯类、醛类、醇类、酮类、烯烃类及呋喃类物质;热杀菌后醛类（己醛、(E)-2-己烯醛）、酯类（乙酸乙酯、乙酸己酯）及萜烯类物质（柠檬烯）含量显著下降,而具有不良气味属性的物质（戊醛、α-松油醇、β-大马士酮等）显著增加。由OPLS-DA模型中的S-Plot图及VIP值筛选到可区分鲜汁与热杀菌样本的10种标志性差异物,包括醛类、酯类、萜烯类3大种类物质及(E)-2-己烯醛、己醛、乙酸乙酯、苯甲醛、柠檬烯、乙酸己酯、乙酸叶醇酯7种挥发性物质,该结果验证了感官评价及GC-MS分析的准确性。【结论】 热杀菌导致蟠桃汁清香感丧失严重且产生异味及蒸煮味;己醛、(E)-2-己烯醛、苯甲醛、乙酸乙酯、乙酸己酯、柠檬烯、乙酸叶醇酯7种挥发性物质含量的下降及不良属性物质如戊醛及β-大马士酮的生成是导致热杀菌蟠桃汁清香感丧失、异味及蒸煮味产生的关键因素;基于电子鼻分析、感官评价及GC-MS检测结合PCA/OPLS-DA多元统计分析方法可以准确评价热杀菌对蟠桃汁香气轮廓的影响并追踪热杀菌蟠桃汁风味品质劣变的关键靶点因子,研究结果为后续深入探究蟠桃汁风味品质劣变机制提供了参考。

Effects of Thermal Sterilization on Aroma Quality of Flat Peach Juice Based on Sensory Evaluation and GC-MS Combined with OPLS-DA

【Objective】In order to provide a theoretical basis for the quality control of flat peach juice products, the aroma quality changes and the main deterioration factors of flat peach juice after thermal sterilization were investigated.【Method】 Flat peach juice samples were prepared by using four flat peach varieties from Xinjiang province (Zaolupan, ZLP; Zaopan, ZP; Ruipan1, RP1; Ruipan18, RP18) as raw materials and treated at 85℃ for 30 min. Then, the changes of sensory characteristics and aroma composition were investigated by using E-nose, descriptive sensory evaluation (DSA), and GC-MS. Furthermore, OPLS-DA model was applied to screen the marker compounds which caused the quality changes in thermally sterilized juice.【Result】Descriptive sensory analysis and E-nose results indicated that differences existed among four fresh juices, but all of the fresh samples showed high scores in green, peach-like, floral, and fruity attributes. Whereas, the aroma quality of flat peach juice changed greatly after thermal sterilization, as reflected by the decrease of green attribute and the increase of sweet, off-flavor, and cooked flavor. Seven categories of volatile compounds were identified by GC-MS, including esters, lactones, aldehydes, alcohols, ketones, terpenes, and furan compounds. The concentration of aldehydes (hexanal, (E)-2-hexenal), esters (ethyl acetate, hexyl acetate) and terpenes (limonene) decreased significantly after thermal sterilization, while some compounds with off-flavor attribute (pentanal, α-terpineol, β-damascenone) increased significantly. Ten compounds, including three categories compounds (aldehydes, esters, and terpenes) and (E)-2-hexenal, hexanal, ethyl acetate, benzaldehyde, limonene, hexyl acetate and (Z)-3-hexenyl acetate were screened as markers that could distinguish the fresh juice and thermally sterilized juice according to S-Plot and VIP value of OPLS-DA model, so this result verified the accuracy of sensory evaluation and GC-MS analysis.【Conclusion】 The green attribute significantly decreased, meanwhile off-flavor and cooked flavor attributes emerged after thermal sterilization. The decrease of (E)-2-hexenal, hexanal, ethyl acetate, benzaldehyde, limonene, hexyl acetate and (Z)-3-hexenyl acetate and the formation of pentanal and β-damascenone were the main factors for leading to the loss of green attribute and formation of off-flavor and cooked flavor. GC-MS and sensory evaluation coupled with multivariate statistical analysis method (PCA/ OPLS-DA) could be used to accurately evaluate the effect of thermal sterilization on the aroma profile of flat peach juice, and further to trace the key factors of flavor quality deterioration of thermally sterilized juice, which provided a reference for further exploring the degeneration mechanism of thermally processed juice.