玻璃化转变
罗伊乳杆菌
基质(化学分析)
化学
水活度
单元格信封
扫描电子显微镜
化学工程
脱脂牛奶
造粒
动态力学分析
食品科学
分析化学(期刊)
材料科学
色谱法
乳酸菌
复合材料
发酵
生物化学
聚合物
含水量
有机化学
工程类
岩土工程
基因
大肠杆菌
作者
Arup Nag,Mark R. Waterland,Patrick Janssen,Rachel C. Anderson,Harjinder Singh
标识
DOI:10.1016/j.foodres.2019.04.058
摘要
Lactobacillus reuteri LR6 cells were stabilized using a novel combination of wet granulation and fluidized-bed-drying techniques. The stabilized cells were stored at 37 °C and at two water activity (aw) levels (0.11 & 0.30). Superior storage stability was recorded in the lower aw environment, supported by a stronger glassy matrix when skim milk powder was used as the excipient. The initial viable cell populations of the samples stabilized in different matrices ranged from 8.3 to 9.1 log CFU/g. At the end of the storage period, the viable cell populations were reduced to 6.7 to 7.3 log CFU/g at aw 0.11 and to 6.1 to 6.6 CFU/g when the aw was maintained at 0.30. Fourier transform infrared spectroscopic examination of the cell envelopes revealed substantial dissimilarities between samples at the beginning and at the end of the storage period, which indicated alteration in the secondary protein structures of the cell envelope and also correlated well with the loss in cell viability. In milk-powder-based matrices, adjusting the aw to 0.30 resulted in a weaker or no glassy state whereas the same matrices had a high glass transition temperature at aw 0.11. This strong glassy matrix and low aw combination was found to enhance the bacterial stability at the storage temperature of 37 °C. Scanning electron microscopy revealed the formation of corrugated surfaces and blister-type deformations on the cell envelopes during the stabilization process.
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