Characterization of Volatiles in Pasteurized Litchi Juice by Treatment and Fermented Litchi Juice Based on GC-MS and GC-IMS
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Abstract:
Gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) techniques were used to analyze the effects of thermal pasteurization (TP) and high hydrostatic pressure (HHP) on the volatiles in litchi juice and lactobacillus fermented litchi juice. From the results, 70 volatiles were identified by GC-IMS, including ketones, alcohols, esters, aldehyde, and terpenoids. The TP process resulted in a severe loss of ethyl propionate, methyl 2-methylpropanoate, benzyl alcohol, and 1-octene-3-alcohol in fresh litchi juice, whereas volatiles such as butyl propionate, trimethylpyrazine, 5-nonone and 2,5-dimethylthiophene were more abundant after fermentation. The volatiles in HHP pretreated juice were similar to those in fresh litchi juice, and compounds such as linalool, 2,6-dimethylpyrazine, cis-rose ether, and benzaldehyde were more abundant in its fermented juice; 51 volatiles were identified by GC-MS, mostly comprising terpenoids and alcohols. The TP process decreased the contents of terpenoids and alcohols in litchi juice by 37.05% and 31.61% respectively. Compared with the fresh juice, terpenoid and alcohol content in HHP litchi juice increased by 33.57% and 80.07% respectively. The total content of volatiles in TP and HHP fermented litchi juice increased by 46.93% and 46.19% respectively, compared with the pretreated juice. The content of volatiles in HHP fermented litchi juice was 2.11 times higher than that in the TP fermented juice, with a more pleasant aroma. The combination of the two technologies shows that HHP pretreatment can effectively improve the aroma quality of litchi juice and fermented litchi juice, providing a reference value for improving the quality of fermented litchi juice.
