荔枝汁高密度二氧化碳杀菌研究

Inactivation of microbe in fresh lychee juice exposed to high dense phase carbon dioxide

研究新鲜荔枝汁以及新鲜荔枝汁37℃自然培养12、24h后,细菌总数、霉菌与酵母菌总数变化,考察高密度二氧化碳(HDCD)对荔枝汁中天然菌的杀菌效果。实验结果显示,新鲜荔枝汁中初始细菌总数、霉菌与酵母总数分别为106·5、105·5cfu/mL,37℃自然培养12h后,细菌总数增加1·5个数量级,霉菌和酵母略有减少;37℃自然培养24h后,细菌总数、霉菌和酵母均无增长。新鲜荔枝汁、37℃自然培养12h、37℃自然培养24h荔枝汁经HDCD处理,细菌总数分别降低4·5、4·8、5·9个数量级,霉菌和酵母被杀灭。对杀菌前后的荔枝汁中天然微生物的菌落形态进行观察,结果显示,杀菌前后荔枝汁中微生物的菌落形态有显著区别,荔枝汁中优势菌基本被杀灭,但也有些微生物能耐受8MPa的高密度二氧化碳。

Total number of bacteria,mold and yeast in fresh lychee juice and natural cultivation at 37 ℃ for 12,24h,effect of HDCD treatment on sterilization of lychee juice was investigated. The result revealed that initial bacteria and yeast and mould number in fresh juice were 106.5,105.5respectively. After nature cultivation at 37℃ for 12h,the bacteria number increased 1.5 in logarithm,but the yeast and mold number had a little decrease;nature cultivated at 37℃ for 24h,bacteria number and total fungi number had no increase. The reduction of the total count of bacteria colonies in fresh-squeezed lychee juice,lychee juice that nature cultivated 12h,that cultivated 24h reached to 4.5,4.8,5.9 in logarithm,when exposed to HDCD at 8MPa,36℃,for 0min,respectively. Yeast and mold were completely killed by HDCD treatment at the same condition. Colony morphology characteristic of the natural microorganism in the treated and untreated lychee samples were observed,the results showed that there was obvious difference in colony. Almost all predominant bacteria in lychee juice were killed,but some germ can tolerate 8Mpa HDCD treatment.