基于GC-IMS结合化学计量学分析不同冷冻时长对椰子水挥发性物质的影响

Effect of Frozen Periods on Volatile Flavor Compounds of CoconutWater Based on GC-IMS and Chemometrics Analysis

采用气相色谱-离子迁移谱(GC-IMS)和化学计量法,研究了成熟椰子水在-18℃冷冻0、1、2和3个月(CW0、CW1、CW2和CW3)后挥发性物质的变化。结果表明:GC-IMS能够从成熟椰子水中鉴定出29种挥发性有机物,包括13种醇类、6种酯类、6种醛类、2种酮类、2种酸类物质。经冷冻后,挥发性物质的总量(峰值体积)发生了显著的降低和散失。随着冷冻时间的延长,酸类化合物峰体积逐渐增强并在冷冻第2个月后达到最大值,而后降低。醇、酯、醛类物质峰体积逐渐上升并在冷冻第三个月后达到最大值,酮类物质峰体积逐渐降低,并在冷冻2个月之后达到最小值。主成分分析(PCA)和正交偏最小二乘判别分析(OPLS-DA)均能在不过拟合的情况下对4种椰子水进行判别;进一步从鉴定出的挥发性物质中,根据可变重要性投影(VIP)值>1选取9个关键标志物,在聚类热图分析中分别实现对4种椰子水的聚类和有效区分,其中乙酸乙酯(D、M)、异丁醛、乙醛、己酸乙酯、2-丁酮、乙酸(M)可作为椰子水不同冷冻时长的阶段标志物。研究结果为不同冷冻时间下椰汁的GC-IMS快速鉴别提供了依据。

In this paper,gas chromatography-ion mobility spectroscopy(GC-IMS)and chemometrics were used to investigate the changes of volatile substances in mature coconut water after freezing at-18℃for 0,1,2 and 3 months(CW0,CW1,CW2 and CW3).Results showed that GC-IMS could identify 29 volatile substances from four kinds of coconut water,including 13 alcohols,6 esters,6 aldehydes,2 ketones and 2 acids.And the total amount(peak volume)of volatile substances decreased significantly with the extension of freezing periods.As the extension of freezing periods,the peak volume of acid compounds gradually increased and reached a maximum value in the coconut water freezing for two month(CW2)and then decreases.The peak volume of alcohols,esters,and aldehydes gradually increased and reached a maximum value in the coconut water freezing for three month(CW3),while the peak volume of ketones gradually decreased and reached a minimum value in the freezing coconut water for two month(CW2).Both principal component analysis(PCA)and orthogonal partial least squares discriminant analysis(OPLS-DA)could distinguish four kinds of coconut water without over-fitting.Furthermore,9 key markers were selected from the identified volatile substances based on the variable importance projection(VIP)value>1,which could achieve the respective clustering and effective differentiation of four coconut water in the cluster heat map analysis.Among them,ethyl acetate(D,M),isobutyral,acetaldehyde,ethyl caproate,2-butanone,acetic acid(M)were the characteristic volatile substance of coconut water of different freezing periods.These results would provide support for the rapid identification of coconut water by GC-IMS at different freezing periodss.