即食小龙虾保鲜剂的复配及其抑菌机理的初步研究

发布时间：2018-03-27 22:25

本文选题：小龙虾　切入点：优势腐败菌　出处：《合肥工业大学》2017年硕士论文

【摘要】：小龙虾营养价值丰富且味道鲜美,目前是我国市场上最畅销的淡水虾之一。但因其大多采用鲜活销售的方式,受地域和季节的影响较大,且小龙虾水分、蛋白质含量高,极易感染微生物而腐烂变质,难以保藏。本文以鲜活小龙虾为材料,通过油炸、蒸煮、杀菌、包装制成即食小龙虾产品,结合加工工艺和优势腐败菌的特性进行防腐保鲜实验,来解决小龙虾容易腐败、货架期短的问题,这对即食小龙虾的防腐保鲜有着重要的现实意义。研究内容包括以下几个方面:(1)通过传统平板分离纯化方法,从腐败终点的即食小龙虾中分离出全部腐败菌,通过形态观察、染色和镜检对其进行分类,再通过测定各种菌的菌落增长数和挥发性盐基氮(TVB-N)的值,并以产量因子Y(TVB-N/CFU)判定致腐能力,确定优势腐败菌,最后对优势腐败菌进行形态学鉴定、生理生化实验和16S rRNA分子生物学鉴定。研究表明:从小龙虾中共分离得到186株菌落,归为4类,得出3号菌的腐败能力最强,且占菌落总数的86.02%,比重最大,确定为优势腐败菌,鉴定结果为柠檬酸杆菌Y3(Citrobacter murliniae Y3)。(2)在最小抑菌浓度(MIC)和单因素实验的基础上,通过响应面实验设计,以菌落总数为评价指标,得出复合保鲜剂的最佳配比。结果表明:山梨酸钾、脱氢乙酸钠、ε-聚赖氨酸和壳聚糖对即食小龙虾的保鲜效果较好,且最佳使用浓度分别为0.50 g/L、0.31 g/L、0.21 g/L和2.84 g/L,用该复合保鲜剂处理即食小龙虾,能够有效减缓小龙虾感官品质的下降,显著降低微生物的数量、延缓pH值、TVB-N含量、TBA值和K值的增长,使其货架期由6 d延长至30 d。(3)以分离得到的柠檬酸杆菌Y3为研究对象,利用酶标板法确定复合保鲜剂的MIC,通过细菌生长曲线、细胞壁通透性、细胞膜通透性和扫描电镜观察细菌微观形态来确定复合保鲜剂的抑菌机理。研究表明:复合保鲜剂对柠檬酸杆菌Y3的MIC为0.483 g/L,菌液经MIC浓度的保鲜剂处理后,细菌的生长曲线发生较大的变化,细菌生长受到严重抑制;菌液中的AKP酶含量增加,细胞壁的通透性增加;细胞膜的通透性也变大,菌液的电导率、紫外吸收值、可溶性糖和蛋白均明显上升;扫描电镜下观察到菌体微观形态受到严重破坏,边缘模糊不清,菌体内部严重破损和断裂,细胞壁溶解,细胞质从菌体细胞体内大量渗出。通过机理实验可以初步得出,其抑菌机理可能是复合保鲜剂通过破坏细胞结构的完整性,使菌体细胞壁和细胞膜受到损伤,从而抑制细菌生长和杀死细菌。
[Abstract]:Crayfish is one of the best-selling freshwater shrimps in our country because of its rich nutritive value and delicious taste. However, it is influenced greatly by region and season, and its water content and protein content are high. It is easy to infect microbes and decay and deterioration, which is difficult to preserve. In this paper, fresh crayfish is used as material, which is made into ready-to-eat crayfish products by frying, cooking, sterilizing and packaging. The experiments of anticorrosion and preservation are carried out by combining the processing technology and the characteristics of dominant spoilage bacteria. To solve the problem of easy spoilage and short shelf life of crayfish, this is of great practical significance to the preservation and preservation of instant crayfish. All spoilage bacteria were isolated from instant crayfish with spoilage endpoints. They were classified by morphological observation, staining and microscopic examination, and the number of colony growth and the value of TVB-N of volatile base nitrogen were determined. The yield factor YTVB-N / CFU was used to determine the ability to cause rot, to determine the dominant spoilage bacteria, to identify the dominant spoilage bacteria by morphology, physiological and biochemical experiments, and to identify the molecular biology of 16s rRNA. The results showed that a total of 186 colonies were isolated from crayfish. Classified into 4 categories, the result showed that the spoilage ability of No. 3 bacteria was the strongest, and it accounted for 86.02% of the total number of bacteria, and its proportion was the largest, and it was determined as the dominant spoilage bacterium. The result of identification was Y3(Citrobacter murliniae Y3CU) on the basis of minimal inhibitory concentration (MIC) and single factor experiment. The optimum ratio of compound preservative was obtained by using the total number of bacteria as the evaluation index. The results showed that potassium sorbate, sodium dehydroacetate, 蔚 -poly (lysine) and chitosan had better fresh-keeping effect on instant crayfish. The optimum use concentration was 0.50 g / L 0.31 g / L 0.21 g / L and 2.84 g / L respectively. The treatment of instant crayfish with this compound preservative could effectively slow down the decline of sensory quality of crayfish, significantly reduce the number of microorganism, and delay the increase of TBA and K value of TVB-N content in pH value. The shelf life was extended from 6 days to 30 d.) the isolated strain of Bacillus citrate Y3 was used as the research object. The microbes of compound preservative were determined by the method of enzyme label plate. The cell wall permeability was obtained by the growth curve of bacteria. Cell membrane permeability and microscopic morphology of bacteria were observed to determine the bacteriostatic mechanism of the compound preservative. The results showed that the MIC of the compound preservative to Y3 was 0.483 g / L, and the bacteria solution was treated with the preservative of MIC concentration. The growth curve of bacteria changed greatly, the growth of bacteria was seriously inhibited, the content of AKP enzyme in bacterial solution increased, the permeability of cell wall increased, the permeability of cell membrane also became larger, the conductivity of bacterial solution and ultraviolet absorption value increased. Under scanning electron microscope, the micromorphology of the bacteria was seriously destroyed, the edges were blurred, the interior of the bacteria was seriously damaged and broken, and the cell wall was dissolved. Through the mechanism experiment, it can be preliminarily concluded that the bacteriostatic mechanism may be that the compound preservative may damage the cell wall and cell membrane by destroying the integrity of the cell structure. Thus inhibiting bacteria growth and killing bacteria.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TS254.4

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