豆豉返霜过程中基本理化特性及微生物多样性差异分析

通过测定豆豉在返霜过程中水分、灰分、粗蛋白、粗脂肪、总糖、还原糖、总酸、氨基态氮含量、氨基酸组成以及返霜前后微生物的变化,研究返霜前后其基本理化特性和微生物组成的变化规律。结果表明,随着返霜的进行,豆豉中灰分和总糖含量基本保持不变,粗脂肪、还原糖、总酸含量整体呈下降趋势,水分含量先增加后基本保持稳定;氨基态氮含量在贮藏前6d内与粗蛋白含量变化趋势相反,且氨基酸评分结果显示,返霜后豆豉中蛋白质营养价值降低。Illumina Miseq测序结果表明,返霜后,豆豉的细菌和真菌OTUs都有所降低,细菌芽孢杆菌属增加,真菌曲霉属减少。因此,返霜会降低豆豉的营养价值及细菌群落多样性,增加真菌群落多样性,破坏豆豉原有的特色菌群组成结构。

Variation in physicochemical properties and microbial diversity during the progression of efflorescence on the surface of Douchi

The changes in basic physicochemical properties and microbial diversity of Douchi before and after efflorescence of the surface were evaluated. The physicochemical properties were investigated via determining the content of moisture, ash, crude protein, crude fat, total sugar, reducing sugar, total acid, and amino nitrogen, along with the amino acid composition. The microbial diversity was measured by Illumina Miseq sequencing. The results showed that, with the progress of efflorescing, the ash and total sugar content of Douchi exhibited insignificant changes, and the crude fat, reducing sugar and total acid content showed a downward trend as a whole. The moisture content increased first and then kept stable. An adverse trend was observed on amino nitrogen content as compared to that of the crude protein content between 0~6 days. The amino acid score illustrated that the nutritional value of protein decreases after efflorescing. According to the results of Illumina Miseq sequencing, the bacteria and fungi OTUs of Douchi were all reduced after efflorescing, and the ratio of Bacillus in bacteria was increased, with the ratio of Aspergillus in fungi reduced. Therefore, the efflorescing would reduce the nutritional value of Douchi and decrease the diversity of bacterial community. However, the diversity of fungal community could be increased, with the destroy of the original flora composition.