【作者】 王宁；

【导师】 王清章；

【作者基本信息】 华中农业大学 ， 农产品加工与贮藏， 2007， 硕士

【摘要】 鲜肉的保鲜是我国肉类工业发展中急需解决的问题，同时也是制约我国冷却肉市场化的主要瓶颈。本文以冷却羊肉为试验材料，对导致其腐败的主要微生物进行了分离和初步鉴定，并对腐败菌的初始菌相构成及其在贮藏过程中的消长情况进行了分析，进而探讨了不同包装形式对菌相消长的影响，分析了5种天然保鲜剂的抑菌特性，并从中筛选出3种进行复合，通过旋转组合设计对复合保鲜液的配方进行优化，考察了其综合保鲜效果。本文不仅为冷却羊肉腐败菌相的研究提供了理论依据，而且所采用的复合保鲜液处理+气调包装+4℃冷藏的保鲜方法能将冷却羊肉的货价期延长至42d，具有非常重要的现实意义。1．按照Brown MH（1982）推荐的肉品微生物鉴定图谱，通过观察菌落特征和菌株的菌体形态、革兰氏染色情况，并结合生理生化特征，从冷却羊肉中分离和初步鉴定出乳酸菌21株（13株球菌，8株杆菌），热死环丝菌8株，假单胞菌属12株，肠杆菌科13株，未知菌4株。2．采用选择性培养基对冷却羊肉中主要腐败菌进行了选择培养，分析研究了腐败菌的初始菌相构成及其在真空贮藏过程中的消长规律。结果表明：假单胞菌属、乳酸菌、热死环丝菌和肠杆菌科4类菌占菌落总数的90.50％，其含量分别为29.25±3.07％、29.75±2.26％、27.50±3.13％和4.01±1.82％；真空条件下，乳酸菌的含量逐渐上升，并快速成为绝对优势菌群，热死环丝菌和假单胞菌属的含量逐渐下降，肠杆菌科的含量变化不大。3．采用托盘包装、真空包装、MAP₁（25％CO₂+75％N₂）、MAP₂（25％O₂+30％CO₂+45％N₂）和MAP₃（70％O₂+20％CO₂+10％N₂）5种形式对冷却羊肉进行包装，考察了不同气体条件对冷却羊肉菌相构成的影响。结果表明：高氧环境下（托盘包装和MAP₃），菌落总数和4种腐败菌尤其是假单胞菌属和肠杆菌科的数量明显高于低氧（MAP₂）和无氧包装（真空包装和MAP₁）。低氧和无氧环境由于低氧分压以及CO₂的抑菌作用，使假单胞菌属的生长受到很大程度地抑制，但乳酸菌仍能较快生长并迅速成为优势菌群，而肠杆菌科和热死环丝菌的比例变化不大。另外，假单胞菌属和肠杆菌科对CO₂很敏感，乳酸菌和热死环丝菌对CO₂相对不敏感。5种包装以MAP₂的综合抑菌效果最为理想。4．选取Nisin、溶菌酶、乳酸钠、茶多酚和壳聚糖5种保鲜剂对冷却羊肉进行处理后进行MAP₂（25％O₂+30％CO₂+45％N₂）包装，分析研究了不同保鲜剂的抑菌效果和对腐败菌菌相构成的影响。结果表明：5种保鲜剂的综合抑菌效果依次为Nisin＞溶菌酶＞乳酸钠＞壳聚糖＞茶多酚；Nisin和溶菌酶对革兰氏阳性的乳酸菌和热死环丝菌有很好的抑制作用，而对革兰氏阴性的假单胞菌属和肠杆菌科的抑制作用较差。乳酸钠对假单胞菌属有较强的抑制作用，对热死环丝菌和肠杆菌科也有一定的抑制作用，对乳酸菌的抑制作用较差。壳聚糖对假单胞菌属、热死环丝菌和肠杆菌科均有一定的抑制作用，对乳酸菌的抑制作用较差。茶多酚对假单胞菌属和肠杆菌科有一定的抑制作用，对乳酸菌和热死环丝菌的抑制作用较差。5．采用三因子二次正交旋转组合设计方案，对Nisin、溶菌酶和乳酸钠组成的复合保鲜剂的配方进行优化，并对其综合保鲜效果进行检验。结果表明：优化所得的复合保鲜剂为0.38％Nisin+0.27％溶菌酶+2.90％乳酸钠，通过与复合对照组、单因素组和空白组，在感官评价、pH值、TVB-N值和菌落总数方面的对比来看，复合保鲜剂的综合保鲜效果优于单一保鲜剂，更优于空白。其中以优化所得的复合保鲜剂的综合保鲜效果最为理想，故将复合保鲜剂的配方最终定为Nisin 0.38％、溶菌酶0.27％、乳酸钠2.90％。冷却羊肉经此保鲜液处理后进行气调包装（25％O₂+30％CO₂+45％N₂），在4±1℃下冷藏至42d时，各项评价指标均符合GB2708-1994。更多还原

【Abstract】 Meat preservation has long been one of the problems demanding urgent solution inmeat industry development, which is also a key bottleneck inhibitting the marketabilityof chilled meat. In this paper, chilled mutton was looked as experimental material andseveral steps were carried out to inhibit the reproduction of spoilage bacteria. First of all,main types of spoilage bacteria were separated and identified primarily, and then initialmicroflora and its change during the storage were analyzed. Secondly, how differentways of package affected microflora change was studied. Thirdly, five antimicrobialswere selected to inhibit the growth of the main types of spoilage bacteria. Finally, anoptimum compound antimicrobial was obtained by three factors quadratic rotating designto prolong the shelf-life of chilled mutton. This paper not only provided a theory basis forthe farther research on the spoilage bacteria in the chilled mutton, but also could prolongthe shelf-life of chilled mutton to 42 days by treated with the optimum compoundantimicrobial, packed in modified atmosphere and stored at 4℃.1. Main types of spoilage bacteria in chilled mutton was separated and purified.With meat microbial identification manual, 21 Lactobacillus, 8 B. thermosphacta, 12Pseudomonas and 13 Enterobacteriaceae were primarily identified according to the formof bacteria, the characteristic of microflora and biochemical experiments. But there arealso 4 bacteria couldn’t be identified with this method.2. Main types of spoilage bacteria in chilled mutton were incubated with selectiveagars to analyze initial microflora and its changes in vacuum condition. The resultshowed: Pseudomonas, Lactobacillus, B. thermosphacta and Enterobacteriaceae accountfor 90.50% of total bacteria counts, and their contents respectively were 29.25±3.07%,29.75±2.26%, 27.50±3.13% and 4.01±1.82%; Lactobacillus grew rapidly and fastbecame dominant microflora during the storage. However, Pseudomonas and B.thermosphacta decreased gradually. Enterobacteriaceae almost unchanged.3. Chilled mutton was packed with 5 types of atmospheres-air, 25%CO₂+75%N₂（MAP₁）, 25%O₂+30%CO₂+45%N₂ （MAP₂）, 70%O₂+20%CO₂+10%N₂ （MAP₃） andvacuum package. Main spoilage bacteria in chilled mutton were incubated with selectiveagars to analyze the effect of atmosphere on spoilage bacteria and the change of microflora during the storage. The result showed: in air package and MAP₃, because ofthe presence of oxygen, total bacteria count and all types of spoilage bacteria especiallyPseudomonas and Enterobacteriaceae were higher than other packages. Lowconcentration of oxygen or high concentration of CO₂ could inhibit the growth ofPseudomonas in vacuum package, MAP₁ and MAP₂. But Lactobacillus could grewrapidly and fast become dominant microflora. However, Enterobacteriaceae and B. ther-mosphacta were almost unchanged. In addition, Pseudomonas and Enterobacteriaceaewere more sensitive to CO₂ than Lactobacillus and B. thermosphacta. MAP₂ was the bestideal package to inhibit the growth of spoilage bacteria.4. Five nature antimicrobials-nisin, lysozyme, lactic acid sodium, tea polyphenol andchitosan-were selected to inhibit the growth of spoilage bacteria in chilled mutton. Maintypes of spoilage bacteria were incubated with selective agars to analyze the antisepticeffect of antimicrobials. The result showed: in the factor of antiseptic effect, nisin＞lysozyme＞lactic acid sodium＞chitosan＞tea polyphenol. Nisin and lysozyme couldinhibit the growth of gram-positive bacteria like Lactobacillus and B. thermosphacta.Lactic acid sodium could inhibit the growth of Pseudomonas well. In a certain extent, B.thermosphacta and Enterobacteriaceae could also be inhibited. Chitosan could inhibitthe growth of B. thermosphacta, Pseudomonas and Enterobacteriaceae. Tea polyphenolcould inhibit the growth of Pseudomonas.5. The concentration of the optimum compound antimicrobial constituted with nisin,lysozyme and lactic acid sodium were decided by three factors quadratic rotating design.Then its comprehensive preservation effect was inspected. The result showed: Nisin（0.38%）+lysozyme（0.27%）+lactic acid sodium（2.90%） could constitute the optimumcompound antimicrobials. By comparing in sensory evaluation, pH value, TVB-N valueand total bacteria counts, it was found that its comprehensive preservation effect wasbetter than others. So the formula of compound antimicrobial could be decided as Nisin（0.38%）, lysozyme （0.27%）, lactic acid sodium （2.90%）. Chilled mutton treated with thiscompound antimicrobial, packed in 25%O₂+30%CO₂+45%N₂, and then stored at 4±1℃.At the 42 days, its each evaluation fit GB2708-1994 completely.更多还原