一株西藏灵菇嗜热链球菌产胞外多糖的流变学特性

以一株西藏灵菇嗜热链球菌为研究对象,系统地研究质量浓度、剪切速率、热处理、pH及盐离子对其所产胞外多糖流变学特性的影响。结果表明,该胞外多糖溶液具有良好的增稠性,质量浓度为8.6 mg/mL时其黏度可达到85.63mPa.s;多糖溶液呈高度假塑性,剪切稀释现象明显;热稳定性差,当温度由20℃升至100℃时,其黏度下降了74.4%,分别于60,80℃热处理150min,对多糖溶液黏度有不同程度的影响;多糖溶液黏度在酸性条件下相对稳定,但在中性和碱性条件下明显升高;并且随Ca2+浓度升高,多糖溶液黏度显著下降。

Rheological properties of the exopolysaccharide produced by streptococcus thermophilus from tibetan kefir grain

The rheological properties were studied of the exopolysaccharides(EPS) produced by a Streptococcus thermophilus strain from Tibetan kefir grain.The results showed that the aqueous EPS solution was a typical non-Newtonian pseudoplastic fluid,and its flow behavior was affected by its concentration,shearing rate,heat treatment,pH and Ca2+.The EPS had good abilities of thickening,its viscosity was 85.63 mPa·s when concentration was 8.6 mg/mL.The aqueous EPS solution had pseudoplastic characteristics,its viscosity decreased by 69.9% when shearing rate increased from 20 to 60 r/min.The EPS is unstable during heat treatment,its viscosity decreased by 74.4% when temperature rose from 20 to 100 ℃,when heated at 60 ℃ and 80 ℃ for 150 min individually,its viscosity was influenced to some degrees.The EPS solution at pH 2-6 was relatively stable,while its viscosity at pH 8 and pH 10 greatly increased.The viscosity of EPS decreased markedly with Ca2+ concentration increasing.