A Survey Of The Microbial Community From Litopenaeus Vannamei And The Study Of Bacteriostatic Effect Of O-CMCS And Nisin

Litopenaeus vannamei, because of its thin shell body fat, tender meat, tastes well and moderate price, etc is popular among consumers. However, as a kind of perishable food, Litopenaeus vannamei is easily corrupted and spoiled by bacteria invasion in the process of fishing, transportation, processing and storage. Especially after its death, anaerobic degradation under the action of enzymes, as the decrease of the glycogen and ATP, the shrimp body began to harden, and quickly into stiff period. when ATP is decomposed totally, the composition of shrimp meat is further deg radated, until the deterioration. Shrimp, moreover, the presence of large amounts of polyphenol oxidase in the body, can make the shrimp body surface producing double phenolic substances, and then into non-ferrous quinones substances with high activity, combined with amino acids or proteins into melanin easily, leading to darkness of shrimp. So, how to fresh Litopenaeus vannamei, to extend the storage time, meet the needs of people for its high freshness and safety become problem to be solved.0℃and4℃storage characteristics of Litopenaeus vannamei in this article are studied. Litopenaeus vannamei is soaked coating preser vation with1%,2%of carboxymethyl chitosan (O-carboxymethyl chito san, O-CMCS) and0.1%,015%of Nisin, verify its application in prawn preservation.The main research content and result are as follows:1. Bacteria V3area PCR amplification and DGGE integration of map of head, muscles, intestines, stomach, abdomen line of Litopenaeus vannam ei are used to view the prawn bacteria community structure.Results show that the bacterial flora distribution in has certain similarities and differences in each part of Litopenaeus vannamei, such as Staphylococcus, including Staphylococcus epidermidis and Staphylococcus warneri,mainly in the head, body and abdomen line; Pseudomonas strains are abundant in five parts of Litopenaeus vannamei; Psychrobacter resides mainly in the head, body and stomach; Enterococcus faecalis mainly in head, abdomen line and intestinal tract; Shewanella mainly in the head and abdomen line, et al.2. Samples:(1) stored in the refrigerator after1month of prawn;(2) just catched fresh prawns (treated with grading, cleaning and so on, but not into the cold storage);(3) just catched fresh prawns (fresh prawns, handl ed without grading, cleaning, etc). The distribution characteristics of microorganisms in the process of4℃is studied.Results showed that the three kinds of the samples have some bacteria in common:Vibrio, Aeromonas, Enterococcus faecalis, Shewanella and Lactococcus garvieae.The peculiar bacteria of I: Clostridium, Proteus vulgaris. The peculiar bacteria of II:Carnobacterium viridians. The peculiar bacteria of III:Streptococcus parauberis, Bacillus, Staphylococcus.3. With concentration of1%and2%of chitosan preservation solution and concentration of0.15%and0.1%of Nisin preservation solution, respect ively, handling prawns, observating Sensory changes of Litopenaeus vann amei and the pH, the total number of bacteria were determined in the pro cess of0℃storage. Sensory evaluation, pH and the total number of bacteria determination results show that the experimental group has an obvious advantage in the process of preservation of Litopenaeus vannamei than the control group. DGGE results show that some strains are more sensitive for preservation processing, such as Vibrio cholera RD1, PYD, S44are most susceptible; Vibrio fluvialis MBTD CMFRI_Vf05are more sensitive to chitosan than to Nisin. Vibrio vulnificus L32is sensitive to both of two preservation products. Pseudomonas sp. AU is relatively sensitive. Two kinds of high concentration of fresh-keeping agents have more effective inhibition to Shewanella JS-7、AK55、MOLA59, appears in the middle and later periods of the storage.Maybe, the fresh-keeping agent of higher concentration has stronger inhibition within a certain scope of concentration of fresh-keeping agent. In addition, preservation processing has a weak effect or almost unaffected on some other strains.