發(fā)布時間：2018-03-27 22:25

  本文選題：小龍蝦　切入點：優(yōu)勢腐敗菌　出處：《合肥工業(yè)大學》2017年碩士論文

【摘要】：小龍蝦營養(yǎng)價值豐富且味道鮮美,目前是我國市場上最暢銷的淡水蝦之一。但因其大多采用鮮活銷售的方式,受地域和季節(jié)的影響較大,且小龍蝦水分、蛋白質含量高,極易感染微生物而腐爛變質,難以保藏。本文以鮮活小龍蝦為材料,通過油炸、蒸煮、殺菌、包裝制成即食小龍蝦產品,結合加工工藝和優(yōu)勢腐敗菌的特性進行防腐保鮮實驗,來解決小龍蝦容易腐敗、貨架期短的問題,這對即食小龍蝦的防腐保鮮有著重要的現(xiàn)實意義。研究內容包括以下幾個方面:(1)通過傳統(tǒng)平板分離純化方法,從腐敗終點的即食小龍蝦中分離出全部腐敗菌,通過形態(tài)觀察、染色和鏡檢對其進行分類,再通過測定各種菌的菌落增長數和揮發(fā)性鹽基氮(TVB-N)的值,并以產量因子Y(TVB-N/CFU)判定致腐能力,確定優(yōu)勢腐敗菌,最后對優(yōu)勢腐敗菌進行形態(tài)學鑒定、生理生化實驗和16S rRNA分子生物學鑒定。研究表明:從小龍蝦中共分離得到186株菌落,歸為4類,得出3號菌的腐敗能力最強,且占菌落總數的86.02%,比重最大,確定為優(yōu)勢腐敗菌,鑒定結果為檸檬酸桿菌Y3(Citrobacter murliniae Y3)。(2)在最小抑菌濃度(MIC)和單因素實驗的基礎上,通過響應面實驗設計,以菌落總數為評價指標,得出復合保鮮劑的最佳配比。結果表明:山梨酸鉀、脫氫乙酸鈉、ε-聚賴氨酸和殼聚糖對即食小龍蝦的保鮮效果較好,且最佳使用濃度分別為0.50 g/L、0.31 g/L、0.21 g/L和2.84 g/L,用該復合保鮮劑處理即食小龍蝦,能夠有效減緩小龍蝦感官品質的下降,顯著降低微生物的數量、延緩pH值、TVB-N含量、TBA值和K值的增長,使其貨架期由6 d延長至30 d。(3)以分離得到的檸檬酸桿菌Y3為研究對象,利用酶標板法確定復合保鮮劑的MIC,通過細菌生長曲線、細胞壁通透性、細胞膜通透性和掃描電鏡觀察細菌微觀形態(tài)來確定復合保鮮劑的抑菌機理。研究表明:復合保鮮劑對檸檬酸桿菌Y3的MIC為0.483 g/L,菌液經MIC濃度的保鮮劑處理后,細菌的生長曲線發(fā)生較大的變化,細菌生長受到嚴重抑制;菌液中的AKP酶含量增加,細胞壁的通透性增加;細胞膜的通透性也變大,菌液的電導率、紫外吸收值、可溶性糖和蛋白均明顯上升;掃描電鏡下觀察到菌體微觀形態(tài)受到嚴重破壞,邊緣模糊不清,菌體內部嚴重破損和斷裂,細胞壁溶解,細胞質從菌體細胞體內大量滲出。通過機理實驗可以初步得出,其抑菌機理可能是復合保鮮劑通過破壞細胞結構的完整性,使菌體細胞壁和細胞膜受到損傷,從而抑制細菌生長和殺死細菌。
[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.
【學位授予單位】：合肥工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TS254.4

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本文編號：1673537