Microbiological Changes of Fresh Fish during/after Storage under Modified Atmospheres

在CO_2和/或N_2环境下对鲜鱼进行了改性气调贮藏的实际应用研究。然而，其中大多数主要是用感官检查、化学分析和细菌总数作为评价储存鱼的保质期的指标。人们认为有必要在MA储存期间/之后进行微生物学研究，以评估MA储存鱼类的防腐潜力和可能的微生物健康危害。本研究的主要目的是了解MA储存对沙丁鱼鱼片微生物发育的影响，以及MA对分离微生物和指示/致病菌的影响。结果表明：(1)在CO_2: N_2= 20:80、50:50和70:30的MA条件下，沙丁鱼片的保质期几乎是空气条件下的3倍。随CO_2浓度的增加，好氧和厌氧细菌的生长均受到抑制。当MA储存的样品暴露在空气中时，细菌数量开始增加。(2) MA保存14 d后，鱼片的初始菌群由弧菌、假单胞菌、莫拉菌等组成，转变为气单胞菌（70-95%），而假单胞菌和弧菌（20%）在对照样品中占主导地位。在MA中保存4天后转移到空气中的样品以假单胞菌（85%）和气单胞菌（10%）为主。(3)对照样品中假单胞菌、弧菌、莫拉菌和不动杆菌的生长在含CO_2的MA环境中受到抑制，而空气单胞菌和乳酸菌在MA环境中保存14 d未受到显著影响。(4)在含CO_2的MA环境下，沙丁鱼肉末上接种的指示菌和致病菌如副溶血性弧菌、金黄色葡萄球菌、鼠伤寒沙门菌和大肠杆菌数量迅速减少。

Several studies have been carried out on the practical application of modified atmosphere (MA) storage of fresh fish in CO_2 and/or N_2. Most of them, however, dealt mainly with the organoleptic inspection, chemical analyses and total bacterial counts as an index to evaluate the shelflife of the stored fish. Microbiological studies during/after MA storage have been thought necessary to evaluate both the preservative potential and the possible microbiological health hazard of MA storage of fish. The main objective of the present study was to obtain the informations about the effects of MA storage on the microbial development of sardine fillet, and the effects of MA on the isolated microorganisms and indicator/pathogenic bacteria. The results were as follows :(1) Sardine fillets packed under MA (CO_2 : N_2=20 : 80, 50 : 50 or 70 : 30) showed nearly thrice the shelflife of the control samples with air. Both aerobic and anaerobic bacterial growth were retarded depending on the enriched CO_2 concentration. When MA stored samples were exposed to air, the bacterial counts started to increase. (2) Initial microflora of fillets consisting of Vibrio, Pseudomonas, Moraxella etc. changed to Aeromonas (70-95%) after MA storage for 14 days, while Pseudomonas and Vibrio (20%) became dominant in the control samples. Samples stored in MA for 4 days and then transferred to air were dominated by Psedomonas (85%) and Aeromonas (10%). (3) The growth of the isolates (Pseudomonas, Vibrio, Moraxella, and Acinetobacter) from the control samples before/during MA storage were inhibited under the MA containing CO_2, while the isolates (Aeromonas and Lactobacillus) from the samples under MA for 14 days were not significantly affected. (4) The number of indicator and pathogenic bacteria such as Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella typhimurium and Esherichia coli which were inoculated on the minced sardine meat rapidly decreased under MA containing CO_2.