二次巴氏杀菌对长保质期酸乳品质的影响

Effects of Secondary Pasteurization on the Quality of Long-Term Shelf-Stable Yoghurt

对经不同条件二次巴氏杀菌的长保质期酸乳的黏度、脱水收缩作用敏感性(susceptibility to syneresis,STS)和感官品质进行测定,将长保质期酸乳分别置于25、37℃条件下恒温贮藏,定期测定产品的霉菌、酵母菌数及菌落总数。结果表明:随着二次巴氏杀菌温度的升高,产品的黏度逐渐降低、STS逐渐增大;二次巴氏杀菌条件为60℃、30 s产品的喜好度最高,90℃、30 s杀菌产品的喜好度最低;本研究选择的二次巴氏杀菌条件能将残存的霉菌和酵母菌灭活,产品的菌落总数随着二次巴氏杀菌温度的升高而降低,且贮藏温度越高,产品越容易受到污染。综上所述,选择二次巴氏杀菌条件为70℃、30 s效果最佳。

The viscosity,susceptibility to syneresis（STS） and sensory quality of long-term shelf-stable yoghurt subjected to secondary pasteurization were measured.Moreover,mold and yeast counts and total aerobic plate count were determined at regular intervals during storage at 25 and 37℃.Results indicated that viscosity decreased and STS increased with increasing temperature of pasteurization.The yoghurt produced by secondary pasteurization at 60℃ for 30s was most liked,and the yoghurt produced by secondary pasteurization at 90℃ for 30s was least liked by consumers.The residual molds and yeasts were inactivated by secondary pasteurization under the conditions selected in this study.Furthermore,total aerobic plate count declined with increasing temperature of pasteurization.At higher storage temperature the yoghurt was more susceptible to microbial contamination.Overall,we concluded that secondary pasteurization at 70 ℃ for 30s was optimal.