超高压均质联合二甲基二碳酸盐对荔枝汁中污染菌及其微生物货架期的影响

Effect of ultra high pressure homogenization and dimethyl dicarbonate on the inactivation of indigenous microorganisms in the litchi juice and its microbial shelf-life

研究超高压均质和二甲基二碳酸盐(DMDC)两者单独或联合处理对新鲜荔枝汁的杀菌效果。结果表明:200MPa高压均质处理对荔枝汁中污染菌具有很好的杀菌效果,且随着均质次数的增加,荔枝中污染菌逐渐减少(p<0.05)。但高压均质3次后,残留的污染菌在荔枝汁低温贮藏期间能很快的恢复生长,其微生物货架期不超过15d。新鲜荔枝汁中添加250mg/L的DMDC后,荔枝汁中污染菌数,特别是酵母菌,均呈线性快速下降(p<0.05)。添加DMDC12h后,各种菌的下降不再明显,并在进一步的低温贮藏期间,残留的明串珠菌属表现出较快的生长,其微生物货架期也未超过27d。向高压均质处理后的荔枝汁中添加DMDC后,荔枝汁中仅酵母菌下降明显(p<0.05),而菌落总数和乳酸菌数下降不明显(p>0.05),但其微生物货架期明显比单独高压均质和单独DMDC处理的货架期长,说明两者还是具有一定的联合相加作用。此外,对DMDC和高压均质处理后荔枝汁中残留的污染菌采用16S rDNA或18S rDNA法进行鉴定后,发现主要是芽孢杆菌属、毛霉属和明串珠菌属菌株。

The inactivation of indigenous microorganisms in the litchi juice, by individual or combined treatment of ultra-high pressure homogenization （UHPH）and dimethyl dicarbonate （DMDC）, was investigated in this study.Results indicated that 200MPa of UHPH treatment showed a higher inactivation to indigenous microorganisms in litchi juice, and the inactivation of indigenous microorganisms further increased with the increase of UHPH passes.While the residual microbial counts in the UHPH-treated litchi juice could recover to grow during storage of low temperature and its microbial shelf-life was less than 15d.As 250mg/L of DMDC was added to the litchi juice, indigenous microorganisms of litchi juice, especially yeast, showed a linear decrease.After 12h of DMDC addition, no further decrease in the microbial counts was observed, while the residual Leuconostoc strains recovered to grow during further storage of low temperature, and its microbial shelf- life was less than 27d.Moreover,the yeast showed further decreased as 250mg/L of DMDC was added to UHPH-treated litchi juice, whereas the counts of total aerobic bacteria and lactic acid bacteria showed no significant reduction.But the microbial shelf-life of UHPH combined with DMDC was longer as compared with individual DMDC or UHPH treatment, reflecting DMDC and UHPH had additive effect.In addition,the residual microorganisms in the DMDC- and UHPH-treated litchi juice were also identified using the methods of 16S rDNA or 18S rDNA,and it was found that the residual microorganisms were Bacillus, Leuconostoc and Mucor circinelloides strain.