| In order to improve the quality of prawns during storage, Litopenaeus vannamei and Trachypenaeus curvirostris were selected for storage characteristic analysis. Based on the results, effective bio-preservative was developed to inhibit melanosis and prolong the shelf life of prawns. In order to enrich deep-processed shrimp product and promote the development of ready-to-eat seafood, prawn cooking processing optimization, residue microbe identification and handle factor setting were studied. The main content and conclusion are as followed:1. The major nutrient and amino acid composition in the muscle of Litopenaeus vannamei and Trachypenaeus curvirostris were compared. Changes in sensory quality, pH, TVB-N, K-value, biogenic amines, APC and microflora during storage at 4±1°C were determined. Results showed that the protein content of Trachypenaeus curvirostris was higher than Litopenaeus vannamei, while moisture content was lower. Amino acid composition of the two materials were different. Changes in biochemical indices were similar during storage. However, the initial APC of Trachypenaeus curvirostris was lower. Changes in APC and microflora were different between the two materials. Pseudomonas and Aeromonas were the dominant bacteria for Litopenaeus vannamei, while for Trachypenaeus curvirostris, the dominant bacteria were Pseudomonas and Shewanella. Melanosis in Trachypenaeus curvirostris was more severe.2. 11 strains (7 Gram-negative bacteria, 4 Gram-positive bacteria) isolated from prawns were selected for antibacterial experiments using filter paper dispersion method. Chitosan was determined as the antibacterial component in the presupposed bio-preservative. Based on orthogonal experiment, PA 0.5 g/L, EDTA 0.5 g/L, FH 0.01 g/L and CH 0.5 g/L was determined as the antimelanosis bio-preservative. Shelf life of Trachypenaeus curvirostris doubled by the bio-preservative treatment, and melanosis was effectively inhibited. The cost for treating 1 Kg prawns was only 0.22 Yuan.3. The effects of different heating processing methods on texture of peeled prawns were studied. Based on weight loss, color, texture analysis and sensory evaluation, optimized process parameters were determined as follows: NaCl 2% (w/v), cooking time 3-5 min for Litopenaeus vannamei and 5-7 min for Trachypenaeus curvirostris. The cooking time should be adjusted according to the size of peeled prawns.4. 5 typical strains were isolated from cooked peeled prawns. Based on traditional biochemical methods and 16S rDNA method, the 5 strains were identified to belong to Bacillus spp. Low temperature, or low pH could inhibit the growth of the 5 Bacillus spp. Nisin could be used as the preservative in products due to its relatively high antibacterial activities against Bacillus. The proper concentration was 0.5-1.0 g/L.5. Linear regression equation of OD value to DPA concentration was set up: y=0.0027x+0.0052. This equation was significant (P < 0.01), R2Adj=0.9988. DPA at 10-200μg/mL has good linear relationship with OD value. The DPA leakage rate of 5 Bacillus spores showed an increasing trend with the heating temperature lifting or heating time extending. DPA leakage rate of the 5 Bacillus spore suspensions was 21%-54% at 100°C, 5 min. Pretreatment at 60°C, 20 min could increase the leakage rate about 18%-30%.6. The production process for ready-to-eat peeled prawns was further optimized by setting hurdle factors. Storage stability of the products was evaluated by moisture content, texture, color, APC and sensory determination. Results showed that shelf life of the products processed by the optimized technological conditions were more than 30 days, which was less than 12 days for control samples.
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