渥堆期间水分对浏阳豆豉微生物及品质风味的影响

The effects of moisture on microorganisms,quality,and flavor of Liuyang douchi during the pile fermentation period

目的:通过调控渥堆期间水分提高浏阳豆豉的品质风味。方法:采用宏基因测序技术,结合顶空固相微萃取—气质联用(HS-SPME-GC-MS)技术,研究了曲料不同水分(低35%、中42%、高50%)对渥堆期间浏阳豆豉的细菌群落变化及挥发性组成的影响。结果:渥堆水分对渥堆过程中细菌多样性具有明显的影响:第一次渥堆发酵、第二次渥堆发酵两个阶段棒状杆菌的相对丰度与渥堆水分呈正相关,第一次渥堆发酵阶段葡萄球菌相对丰度与渥堆水分呈负相关,且第二次渥堆发酵阶段中未分类的葡萄球菌和片球菌与渥堆水分呈负相关。中水分渥堆豆豉的挥发性物质种类最丰富,且吡嗪类物质比其他水分渥堆豆豉高,但醛类、酸类含量较低。进一步的相关性分析显示葡萄球菌属对差异性挥发性物质的影响最大,与6种差异性挥发性物质如2,3,5-三甲基吡嗪、2-乙基-3,5,6-三甲基吡嗪、愈创木酚等显著正相关;其次是海洋芽孢杆菌属。结论:渥堆水分通过改变细菌多样性影响浏阳豆豉的品质。

Objective:Pile fermentation is an important process for the formation of Liuyang Douchi flavor,the initial moisture of the douchi qu during pile fermentation could induce the temperature changes which might further affected the microbial community and flavor compounds formation.Methods:In this paper,metagenomic sequencing,combined with headspace solid-phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS),was used to investigate the effects of different moisture(low 35%,medium 42%,high 50%)of the douchi qu on the bacterial community changes and volatile composition of Liuyang Douchi during pile fermentation.Results:The results showed that bacteria in high moisture douchi qu proliferated faster due to the lower center temperature.In detail,the relative abundance of Corynebacterium during the first and second stages of pile-fermentation was positively correlated with pile fermentation moisture,while Staphylococcus during the first stage of pile-fermentation was negatively correlated with pile fermentation moisture;Staphylococcus and Pediococcus during the second stage of pile-fermentation were also negatively correlated with pile fermentation moisture.For volatile compounds,the Douchi pile-fermented with medium moisture had the richest variety of volatile substances,especially pyrazine,but the content of aldehydes and acids were lower.Further correlation analysis showed that Staphylococcus had the greatest impact on differential volatile substances and was significantly positively correlated with six differential volatile substances such as 2,3,5-trimethylpyrazine and 2-ethyl-3,5,6-Trimethylpyrazine,guaiacol,etc.are significantly positively correlated,followed by Oceanobacillus which was significantly positively correlated with five differential volatile substances.Conclusion:The moisture content of pile fermentation affects the quality of Liuyang Douchi by altering bacterial diversity.