College of Food Science, Sichuan Agricultural University, Ya'an 625014, PR China.
Sichuan Liji Lebao Food Co Ltd, Meishan 620031, PR China.
Food Res Int. 2022 Sep;159:111130. doi: 10.1016/j.foodres.2022.111130. Epub 2022 Apr 23.
The occurrence of pellicle on the surface of paocai brine is a common undesirable phenomenon during the multi-rounds of paocai fermentation, which is mainly caused by the growth of microorganisms related to pellicle formation. But the detailed information on these microorganisms and volatile components produced by them, as well as the changes of the microorganisms during the process of paocai recovery, are still rare in the literature. Therefore, the purpose of this study was (1) to analyze the pellicle formation related microorganisms by comparing the differential microorganisms in initial brine and the brine when pellicle occurred through metagenomic sequencing technology, (2) to explore the changes of microorganisms in the fermentation system after addition Baijiu and/or salt, and (3) to further detect the VOCs in paocai samples by gas chromatography-mass spectrometry (GC-MS). The relationship between VOCs and the selected marker microorganisms was also determined. The results showed that the diversity of fungi was increased when pellicle formed, the pellicle formation related microorganisms mainly belonged to six genus, including Kazachstania, Lactobacillus, Pichia, Candida, Lachancea, and Saccharomyces. Apart from the unknown function and basic life activities of microorganisms, the metabolic activities of these pellicle formation related microorganisms were mainly carbohydrate transport and metabolism, and amino acid transport and metabolism. The growth of pellicle formation related microorganisms could be inhibited by adding Baijiu (1.5% v/v), but the addition of salt (7% salt (w/v) did not promote this inhibitory effect. Through PCA analysis, it was found that the VOCs of paocai were significantly affected by adding Baijiu and Baijiu and salt. The undesirable smell at the beginning of pellicle formation may be related to Propanoic acid, hexyl ester, 1,3-Dimethyl-1-cyclohexene, Oxime-, methoxy-phenyl- and Phenylethyl Alcohol.
泡菜盐水表面出现菌膜是泡菜多轮发酵过程中常见的不良现象，主要是由与菌膜形成相关的微生物生长引起的。但是，关于这些微生物及其产生的挥发性成分的详细信息，以及在泡菜回收过程中微生物的变化，在文献中仍然很少见。因此，本研究的目的是：（1）通过比较初始盐水和出现菌膜时的盐水的差异微生物，利用宏基因组测序技术分析菌膜形成相关的微生物；（2）探索添加白酒和/或盐后发酵体系中微生物的变化；（3）进一步通过气相色谱-质谱联用仪（GC-MS）检测泡菜样品中的挥发性有机化合物（VOCs）。还确定了 VOCs 与选定标记微生物之间的关系。结果表明，形成菌膜时真菌的多样性增加，菌膜形成相关的微生物主要属于六个属，包括 Kazachstania、Lactobacillus、Pichia、Candida、Lachancea 和 Saccharomyces。除了微生物的未知功能和基本生命活动外，这些菌膜形成相关微生物的代谢活动主要是碳水化合物的运输和代谢，以及氨基酸的运输和代谢。添加白酒（1.5%v/v）可以抑制菌膜形成相关微生物的生长，但添加盐（7%盐（w/v）并没有促进这种抑制作用。通过 PCA 分析发现，添加白酒和白酒加盐显著影响了泡菜的 VOCs。菌膜形成初期出现的不良气味可能与丙酸己酯、1,3-二甲基-1-环己烯、肟、甲氧基-苯-和苯乙醇有关。
