年糕杀菌工艺及其对年糕中微生物影响的研究

为防止年糕发霉变质同时最大限度保留年糕的风味和品质,研究了酸洗结合水浴处理杀菌工艺的杀菌效果。选取酸洗液体积分数、酸洗时间、水浴温度、水浴时间为考察因素,以年糕初始菌落总数和感官评分为评价指标,设计正交试验对年糕杀菌工艺进行优化,通过传统分离鉴定方法对年糕微生物菌群进行分析。结果表明:各因素对初始菌落总数的影响由大到小依次为水浴时间、水浴温度、酸洗时间和酸洗液体积分数;各因素对年糕感官评分的影响由大到小依次为酸洗液体积分数、水浴温度、酸洗时间和水浴时间;由方差分析可知,只有酸洗液体积分数对感官评分有极显著影响。综合各因素对初始菌落总数的影响,得出最优杀菌工艺为酸洗液体积分数2%、酸洗时间15 min、水浴温度95℃、水浴时间40 min。对年糕中微生物菌群分离鉴定可知,鲜样期年糕中细菌以芽孢杆菌属(Bacillus)、微球菌属(Micrococcus)、产酸克雷伯杆菌属(Klebsiella oxytoca)为主,杀菌后年糕中细菌以芽孢杆菌属为主,其他菌种已被杀死或浓度低于检出限,未被检测到;鲜样期年糕中真菌以青霉属(Penicillium)、曲霉属(Aspergillus)、篮状菌属(Talaromyces)为主,杀菌后年糕中真菌主要为青霉属及少量的篮状菌属。结果表明:酸洗结合水浴杀菌工艺可有效抑制年糕中微生物的生长繁殖,具有较好的抑菌杀菌效果,在常温下年糕货架期可以达到6个月且品质较好。

Study on sterilization process and its effect on microorganisms of rice cake

In order to prevent rice cake from mould and spoilage,while to greatly keep its flavor and quality,bactericidal effect of pickling combined with water-bath sterilization process was studied.The factors including pickling solution volume fraction,pickling time,water-bath temperature and water-bath time were investigated by mean of orthogonal design,with the total number of initial colonies and sensory evaluation as indicators.Traditional isolation and identification methods were applied to analyze the microbial flora of rice cake.Results showed that the influences of factors affecting the total number of initial colonies followed the order,from high to low,water-bath time,water-bath temperature,pickling time,pickling solution volume fraction;the influences of factors affecting sensory evaluation followed the order,from high to low pickling solution volume fraction,water-bath temperature,pickling time,water-bath time.Variance analysis results indicated that only pickling solution volume fraction affected the sensory evaluation significantly.The optimized sterilization conditions were pickling solution volume fraction of 2%,pickling time of15 min,water-bath temperature of 95℃and water-bath time of 40 min.By isolating and identifying microbial flora from rice cake sample,bacteria as Bacillus,Micrococcus,and Klebsiella oxytoca,and fungus as Penicillium,Aspergillus,and Talaromyces were mainly detected in the fresh-keeping rice cake.Meanwhile,the main bacteria and fungus existing in the sterillized rice cake were Bacillus,Penicillium and a small amount of Talaromyces,other bacteria were killed or had low concentration which was lower than the detection limit.The results indicated that sterilization process combining pickling with water-bath sterilization gave rice cake a significant antibacterial effect that could effectively prevent microorganism from growing and reproducting.The shelf life of rice cake could reach 6 months under room temperature.