多组学技术解析客家“红菌豆渣”发酵过程中风味及物质的转化

Multiomics reveal the flavor and compound transformation during the fermentation process of Hakka Hongjundouzha

摘要:

【背景】“红菌豆渣”是闽西客家地区特有的一种传统美食。【目的】解析客家传统发酵食品“红菌豆渣”物质转化、形成具有特殊风味的发酵过程。【方法】分析不同发酵时间“红菌豆渣”样品的感官特征，采用GC-MS/MS广泛靶向代谢组学技术、RNA-seq转录组学测序技术和Label-Free非标记定量蛋白质组学技术分析不同发酵时间样品的风味物质组成，寻找影响菌株发酵的主要差异表达基因和蛋白。【结果】不同发酵时间“红菌豆渣”样品共得到风味物质198种，主要包括(E,E)-2,4-癸二烯醛、(E)-2-己烯醛、1-辛醇、奥苷菊环和2-戊基呋喃等。发酵d2是“红菌”发酵基因转录、表达的主要时期，最多基因参与“红菌豆渣”样品的发酵过程，筛选得到的差异基因、差异蛋白数量最多，分别为2 814个和415个。发酵d3，样品趋于成熟，参与发酵过程的基因及其转录、表达的蛋白数量最少，分别为99个和43个。发酵d2-d3，菌株进行淀粉和糖类的代谢、氨基酸的合成与脂肪酸的代谢，样品的豆腥味下降，产生了许多具有特殊香气的醇、酮、酯类物质，使得样品呈现可持续性感知的鲜味(丰富性)和甜味，样品的硬度、剪切力和咀嚼性增加。发酵d4，“红菌豆渣”样品开始产生了一些指示食品腐败的油脂和氯环己烷、硝基环己烷等物质，使得样品开始老化，产品品质开始下降。【结论】本研究通过多组学联用技术，从分子水平上解析了客家“红菌豆渣”不同发酵时间风味物质的组成及其物质转化的过程，可为提高“红菌豆渣”的发酵效率和品质，促进产品实现高值化的精深加工和走向工业化生产奠定基础。

Abstract:

[Background] Hongjundouzha was a traditional delicacy unique to the Hakka region of western Fujian. [Objective] To analyze the compound transformation and special flavor formation during the fermentation process of the Hakka traditional fermented food Hongjundouzha. [Methods] Analyzedthe sensory characteristics of Hongjundouzha samples collected at different time points of fermentation. GC-MS/MS-based widely targeted metabolomics, RNA-seq-based transcriptomics, and Label-Free quantitative proteomics were used to analyze the flavor composition of samples and identify the main differentially expressed genes and proteins that affect strain fermentation. [Results] A total of 198 flavor compounds were obtained from the samples at different time points of fermentation, mainly including (E,E)-2,4-decadienal, (E)-2-hexenal, 1-octanol, azulene, and 2-pentylfuran. Day two of fermentation was the main period for transcription and expression of genes involved in the fermentation with Neurospora crassa, with the most genes involved in the fermentation process of Hongjundouzha samples. The number of differentially expressed genes and proteins screened out was the highest (2 814 and 415, respectively) on this day. On day three of fermentation, the sample tended to become mature, and the number of genes and proteins involved in the fermentation process was the least, at 99 and 43, respectively. From day two to three, the strain underwent metabolism of starch and sugars, synthesis of amino acids, and metabolism of fatty acids, which were accompanied by a decrease in the beany smell and the production of alcohols, ketones, and esters with special aromas, resulting in a sustainable sense of freshness (richness) and sweetness in the sample. At the same time, the hardness, shear strength, and chewiness of the sample increased. On day four, the Hongjundouzha sample began to produce some oils indicating food spoilage and compounds such as chlorocyclohexane and nitrocyclohexane, causing the sample to age and the product quality to decline. [Conclusion] This study utilized multiomics to elucidate the composition and transformation of flavor compounds in Hakka Hongjundouzha at different time points of fermentation from a molecular level. This can lay a foundation for improving the fermentation efficiency and quality of Hongjundouzha, promoting the deep processing of value-added products, and moving towards industrial production.