构树叶加工前后风味成分变化分析

【目的】以制茶工艺对构树鲜叶进行加工,分析构树叶加工前后游离氨基酸、脂肪酸和挥发性成分的变化,为构树鲜叶的加工利用提供参考依据。【方法】采用国标测定方法分析构树鲜叶和构树叶制品原料中游离氨基酸和脂肪酸等主要成分的含量差异,并采用气相离子迁移谱(GC-IMS)对挥发性组分的变化进行分析。【结果】构树叶加工后游离氨基酸含量减少39.39%,甘氨酸和蛋氨酸消失,鲜味氨基酸天冬氨酸和谷氨酸含量分别提高5.55倍和3.32倍;甜味氨基酸含量减少78.70%,苦味氨基酸含量减少82.88%。加工后不饱和脂肪酸含量下降,饱和脂肪酸种类与含量增加,尤其是十一碳酸(C11:0)含量提高7.16倍,同时增加十七碳酸(C17:0)和二十碳酸(C20:0)2种饱和脂肪酸。GCIMS分析结果表明,构树鲜叶共检测出60种挥发性组分,定性42种已知组分,占总挥发性组分的82.82%;构树叶制品共检测出58种挥发性组分,定性检出39种已知组分,占总挥发性组分的81.05%;构树叶加工后,醛类、醇类和萜烯类物质大幅度减少,而酮类、酯类物质和有机酸大量生成,尤其是增加(E,E)-2,4-己二烯醛、己酸、2-甲基-1-戊醇、2-甲基-1-丁醇、环己酮、2-甲基丁酸乙酯等构树鲜叶中没有的成分,GC-IMS数据库未能鉴定的挥发性成分在构树叶制品中明显增加。【结论】构树叶加工后游离氨基酸和脂肪酸含量下降;醛类、醇类和萜烯类等青香及花果香大幅度减少,而酮类、酯类和有机酸等果香及酸味明显提升,可根据挥发性成分变化规律指导构树叶加工工艺及构树叶制品香气品质的评价。

Flavor composition changes in leaves before and after processing of Broussonetia papyrifera

【Objective】To elucidate the flavor substance changes of Broussonetia papyrifera fresh leaves before and after processed by tea making technology,the free amino acids,fatty acids and volatile components were determined and evaluated. It provided reference for the processing and utilization of the fresh B. papyrifera leaves.【Method】The content free amino acids and fatty acids wereanalyzed by the method of national standard in fresh leaves and leaf products of B. papyrifera.Then,the changes of volatile components was used gas chromatography-ion mobility spectroscopy(GC-IMS)to analyze.【Result】After processed,the free amino acids content was reduced by 39.39% and glycine(Gly)and methionine(Met)were disappeared,asparagic acid(Asp)and glutamic acid(Glu)increased by 5.55 and 3.32 times,respectively.The content of sweet amino acid and bitter amino acid decreased by 78.70% and 82.88% respectively. Unsaturated fatty acids were decreased,butthe types and contents of saturated fatty acids increased,especiallythe content of C11:0 increased by 7.16 times and two kinds of saturated fatty acids C17:0 and C20:0 were newly increased. GC-IMS analysis showed total 60 volatile components were detected in fresh leaves,42 of which were known,accounting for 82.82%. The total of58 volatile components were detected in leaf products,and 39 known components accounting for 81.05%. The aldehydes,alcohols and terpenes would be significantly reduced while ketones,esters and organic acids would be produced in large quantities. In particular,(E,E)-2,4-hexadienal,caproic acid,2-methyl-1-pentanol,2-methyl-1-butanol,cyclohexanone,2-methyl-ethyl butyrate and other ingredients not found in the freshleaves were added. In addition,volatile components that could not be identified by GC-IMS database were significantly increased in the leaf products of B. pyrifera.【Conclusion】Free amino acid and fatty acid in B. pyrifera leaves decrease after processing. The aldehydes,alcohols and terpenes with fresh fragrant and floral smellare significantly decreased,while the ketones,esters and organic acids with fruit and acidity smell are increased. It can guide the processing technology of leaves and the evaluation of aroma quality of products according to the changes of volatile components.