商品化低盐虾酱发酵过程中的微生物群落演替和品质变化

Microbial Community Succession and Quality Change of Commercial Low-Salt Shrimp Paste during Fermentation

为改进新兴的商品化低盐虾酱的发酵工艺,本研究系统地测定了商品化低盐虾酱发酵过程中的主要品质指标变化;运用高通量测序技术,对微生物多样性和群落组成进行动态分析。结果显示,虾酱发酵期间,pH值、丙二醛含量、挥发性盐基氮含量、氨基酸态氮含量、水分质量分数、含盐量和生物胺含量变化范围分别为7.19~6.90、3.09~5.56 mg/kg、44.81~175.05 mg/100 g、1.42~1.63 g/100 g、59.19%~62.40%、11.02%~12.04%和0~113.29 mg/kg;其中,丙二醛含量呈先上升后下降趋势,氨基酸态氮含量、挥发性盐基氮含量和生物胺总量均呈上升趋势。虾酱发酵中后期细菌的多样性指标明显降低,真菌多样性指标下降缓慢。在发酵前期(0~7 d),链球菌属、乳杆菌属是主要优势菌属,在发酵中后期(34~145 d),四联球菌属是主要优势菌属,且四联球菌属是发酵前期和发酵中后期的差异菌属。在真菌属水平上,发酵前期以丝孢酵母属为优势菌属,到发酵中期,假丝酵母菌属和链格孢菌成为优势菌属,发酵后期阶段,假丝酵母菌属成为优势菌属,且3个发酵阶段并无显著差异菌属。Spearman相关性热图表明,与真菌属相比,细菌属与理化指标的相关性更高,表明细菌群落在虾酱发酵过程中占主导地位。其中,四联球菌与挥发性盐基氮、氨基酸态氮、丙二醛均呈正相关,链球菌与生物胺呈显著负相关。发酵至64 d,虾酱品质指标和微生物群落基本保持稳定,提示发酵工艺改进可以考虑缩短发酵时间。本研究结果为改进低盐虾酱的发酵工艺提供了理论基础。

In order to improve the fermentation process of the emerging commercial low-salt shrimp paste,this study systematically analyzed the changes in the major quality indicators during the fermentation process.High-throughput sequencing technology was used to analyze the microbial community diversity and composition.The results showed that during the fermentation of shrimp paste,the pH,malondialdehyde(MDA) content,total volatile basic nitrogen(TVBN)content,amino acid nitrogen content,moisture content,salt content and biogenic amine content fluctuated in the range of 7.19–6.90,3.09–5.56 mg/kg,44.81–175.05 mg/100 g,1.42–1.63 g/100 g,59.19%–62.40%,11.02%–12.04% and 0–113.29 mg/kg,respectively.The MDA content increased and then subsequently decreased.The contents of amino acid nitrogen,TVBN and biogenic amines all showed an increasing trend.At the middle and late stages of fermentation,the bacterial diversity indexes decreased significantly,and the fungal diversity indexes decreased slowly.At the early stage of fermentation(0–7 days),Streptococcus and Lactobacillus were the dominant bacterial genera.During the middle and late periods(34–145 days),Tetragenococcus was the dominant bacterial genus and was differential between the three stages of fermentation.Trichosporon was the dominant fungal genus at the early stage of fermentation.At the middle stage,Candida and Alternaria became the dominant genera.At the late stage,Candida became the dominant genus,and no significantly differential fungal genera were found between the three fermentation stages.The Spearman correlation heat map showed that compared with the fungus genera,the bacterial genera had a higher correlation with the physiochemical indicators,indicating that the bacterial community was dominant in the fermentation process.Tetragenococcus was positively correlated with the TVBN,amino acid nitrogen,and MDA contents;Streptococcus was significantly negatively correlated with the content of biogenic amines.Starting from the 64th day,the quality indicators and microbial community of the shrimp paste remained basically stable,suggesting that shortening the fermentation time can be considered as an option to improve the fermentation process.These results provide a theoretical basis for improving the fermentation process of low-salt shrimp paste.