郫县豆瓣挥发性物质变化规律及特征香气物质形成机理

利用气相色谱-嗅闻仪-质谱联用和电子鼻研究郫县豆瓣中香气化合物形成过程及变化规律。分析原料、制曲、甜瓣子发酵(保温发酵)、后发酵阶段香气化合物的变化,对特征香气物质形成机理进行探究,并对不同阶段的郫县豆瓣香气物质进行相关性分析。结果发现:郫县豆瓣挥发性物质呈现先增加后减少的趋势;苯甲醇转化形成苯甲醛,糠醛主要来源于糖类降解,异戊醇由亮氨酸转化生成,4-乙基苯酚和4-乙基-2-甲氧基苯酚主要来源于椒醅,2,3,5,6-四甲基吡嗪来源于蚕豆,苯乙醇和苯乙醛主要是由微生物代谢合成,3-甲硫基丙醛可能由甲硫氨酸的降解形成。制曲阶段对香气贡献最小,保温发酵期间香气积累较多,椒醅对后发酵前期香气贡献较大,但后期大量椒醅会导致部分香气浓度下降。郫县豆瓣从后发酵开始到后发酵6个月的香气成分变化较小,在后发酵6~12个月期间香气成分出现显著的变化,在后发酵1 a以后挥发性物质呈现逐渐减少的趋势。通过相关性分析表明发酵前期和发酵后期香气物质差异较大。

Pattern of Variations in Volatile Substances and Formation Mechanism of Characteristic Aroma Substances in Pixian Broad-Bean Paste

Gas chromatography-olfactometry-mass spectrometry(GC-O-MS)and electronic nose(E-nose)were used to study the changes in the aroma compounds in Pixian broad-bean Paste during its production process.The changes in aroma compounds were analyzed from the raw material to the starter-making,fermentation at constant temperature,and postfermentation stages.The formation mechanism of characteristic aroma substances was explored,and correlation analysis was carried out on the aroma substances at different stages.The results showed that the number of volatile substances increased initially and then decreased during the fermentation process.Benzaldehyde was mainly converted from benzyl alcohol;furfural was mainly derived from the degradation of sugars;soamyl alcohol was produced by leucine conversion;4-ethylphenol and 4-ethyl-2-methoxyphenol were mainly derived from fermented hot pepper;2,3,5,6-tetramethylpyrazine was derived from board beans;phenylethanol and phenylacetaldehyde were mainly derived from microbial metabolism.Moreover,the degradation of methionine may be responsible for 3-methionyl propanal.The starter-making stage contributed minimally to the aroma,which accumulated mostly during the constant-temperature fermentation stage.Fermented hot pepper made a large contribution to the aroma at the early stage of fermentation but resulted in reduced aroma concentration at the late stage.During the first six months of post-fermentation,the concentration of aroma compounds changed slowly,but dramatically from month 6 to 12;however,it gradually reduced after 1 year.The correlation analysis showed that the aroma substances at the early stage of fermentation were significantly different from those at the late stage.