冷链与断链流通对冰藏大黄鱼品质与微生物多样性的影响

Effects of Cold Chain and Broken-off Cold Chain on the Quality and Microbial Diversity of Large Yellow Croaker(Pseudosciaena crocea) Stored in Ice

研究了冷链和断链流通对冰藏大黄鱼品质及微生物多样性的影响。模拟了冰藏大黄鱼冷链与断链两种流通方式,采用多点温度采集仪实时监测不同流通过程中的温度变化,以感官评定、总挥发性盐基氮(TVB-N)、菌落总数(TVC)与嗜冷菌数(PBC)等指标来评价两种流通方式对大黄鱼品质及微生物数量变化的影响,并应用聚合酶链式反应(PCR)-变性梯度凝胶电泳(DGGE)指纹技术对冰藏大黄鱼冷链与断链流通中的微生物种群多样性进行研究。结果表明,温度波动加速大黄鱼的品质劣变,流通时间与其感官分值、TVB-N值、微生物数正相关,冷链组与断链组样品分别在347h与275h时超出货架期终点,货架期分别为275~347h与203~275h。样品经PCR-DGGE割胶回收测序,腐生葡萄球菌、假交替单胞菌和副溶血性弧菌在大黄鱼流通后期逐渐减少,假单胞菌与嗜冷杆菌开始出现并逐渐增多,同时还有不动杆菌与希瓦氏菌。经综合评价,假单胞菌与嗜冷杆菌为大黄鱼冷链与断链流通过程中贮藏末期的主要优势菌。

Effects of different circulation methods (cold chain and broken-off cold chain) on the quality and microbial diversity of large yellow croaker(Pseudosciaena crocea) with ice were researched in this paper.Low temperature preservation is one of the most widely used methods and cold chain logistics is a system engineering,which based on freezing technology and artificial refrigeration technology so as to guarantee the freshness of aquatic products in the periods of production,storage,transportation,sale and consumption in the prescriptive low temperature environment (0-4 ℃) all the time.But it is difficult to maintain the specified temperature in storage and transportation process for the limited conditions and high cost,so the samples were easy to be exposed at room temperature,which was represented by broken-off cold chain.Cold chain and broken-off cold chain of large yellow croaker with ice were simulated in the period of logistic process: samples in cold chain group (T1) were stored at 4 ℃ all the time,while samples in broken-off cold chain group(T2) were simulated the actual logistics process,stored at 20 ℃ when moving,transportation,distribution and sale for 2 h,24 h,8 h and 1 h respectively,then stored at 4 ℃ until the end of storage.The real-time temperature of samples in cold chain group and broken-off cold chain group were monitored respectively by multi-point temperature acquisition instrument.Sensory,physicochemical and microorganism indicators as Total Volatile Base Nitrogen(TVB-N),Total Viable Counts (TVC) and Psychrophilic Bacteria Counts (PBC) were evaluated for the quality changes of large yellow croaker with ice during logistics process.The number and species changes of microorganism in samples of two different circulations were analyzed by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis(PCR-DGGE) fingerprint technology.It was found that the fluctuation of temperature between outer space and inside of box in T1 has little difference,and temperature in the center of fish body has no obvious change.However,there were great changes in temperature between outer space and inside of box in T2,when moving,transportation,distribution and sale were under the condition of 20 ℃,and the temperature of fish body in center has apparent fluctuation during the logistics process.The results showed that the deterioration of samples could be accelerated for temperature fluctuation.Circulation time was positively correlated with sensory score,microbial number and TVB-N value.Samples in cold chain and broken-off cold chain exceeded the end of shelf-life at 347 h and 275 h,TVC were (6.93±0.03)lg(CFU/g) and (6.50±0.07)lg(CFU/g),PBC were (7.50±0.05)lg(CFU/g) and (6.82±0.04)lgCFU/g,TVB-N value were (33.47±1.12)mgN/100g and (31.04±0.06)mgN/100g respectively.The results of PCR-DGGE demonstrated that the number of Staphylococcus saprophyticus,Pseudoalteromonas sp.,Vibrio Parahemolyticus decreased,but the number of Pseudomonas sp.and Psychrobacter sp.increased gradually in later circulation,Acinetobacter sp.and Shewanella sp.were also occupied a certain proportion.In conclusion,the shelf-life of large yellow croaker in cold chain and broken-off cold chain were 275-347 h and 203-275 h respectively.Pseudomonas sp.and Psychrobacter sp.were the special spoilage organism of large yellow croaker in the later of cold-chain and broken-off cold chain process.