二甲基二碳酸盐对荔枝汁的杀菌效果及其耐受菌的分离鉴定

Inactivation of indigenous microorganisms in the litchi juice by Dimethyl Carbonate and identification of resistant microorganisms to DMDC

研究了处理温度和时间对二甲基二碳酸盐(DMDC)在新鲜荔枝汁中杀菌效果的影响,并测定了新鲜荔枝汁经DMDC处理后在4℃贮藏期间微生物的动态变化。结果发现,提高温度能提高DMDC的杀菌速率,缩短杀菌时间,但不能提高总的杀菌效果。4℃的荔枝汁添加DMDC 12 h后,酵母菌已经被完全杀灭,菌落总数、乳酸菌数和霉菌数分别降低至3.73、2.6和0.3个对数。DMDC处理后残留的污染菌采用16S或18S rDNA法进行鉴定后发现其主要是芽孢杆菌属、毛霉属和明串珠菌属菌株,其中明串珠菌属是优势菌群。DMDC处理后的荔枝汁在4℃贮藏期间,残留的明串珠菌能表现出生长,贮藏40 d后,其菌数将达到5个对数以上,会对荔枝汁的营养和风味产生影响。

In the study, effects of temperature and time on the inactivation of microorganisms of fresh litchi juice by dimethyl carbonate （DMDC） were investigated, and the changes in the counts of microorganisms of DMDC-treated fresh litchi juice during storage at 4℃ were also determined. Results showed that the inactivation rate of microorganisms increased with the increasing temperature. But the increase of the temperature could not increase the inactivation of microorganisms, which only decreased the inactivation time of microorganisms. After adding 250 mg/L of DMDC for 12 h, a complete inactivation of yeasts was observed, and the counts of total bacteria, lactic acid bacteria and mold declined to 3.73, 2.6 and 0.3 lg （CFU/mL）, respectively. The identification using 16S or 18S rDNA methods found the residual microorganisms in DMDC-treated litchi juice mainly were Bacillus, Mucor and Leuconostoc strains, and the Leuconostoc was the dominant strains. The residual Leuconostac strains in DMDC-treated litchi juice showed growth during storage of 4℃, after 40 d of storage, the count of Leuconostoc strains reached more than 5 lg, which impacted the nutritional quality and flavor of litchi juice.