【作者】 曹荣；

【导师】 薛长湖；

【作者基本信息】 中国海洋大学 ， 水产品加工及贮藏工程， 2009， 博士

【摘要】 为解决对虾容易黑变和腐败变质,货架期短的问题,本文以海捕鹰爪虾和养殖南美白对虾为研究对象,对其营养成分和贮藏特性进行了对比分析,研制了一种不含亚硫酸盐的复合型防黑变生物保鲜剂,并验证了其在对虾保鲜及防黑变中的作用。为丰富我国虾类深加工产品的种类,促进即食水产品的发展,本文在虾仁熟制加工工艺,煮制加工过程中残留微生物的种类鉴定及性质分析,栅栏因子的设置以及贮藏过程中产品的稳定性等方面进行了系统研究,为即食虾仁产品的生产和保鲜提供了一定的理论依据和技术支持。主要研究内容和结论分述如下:1.对海捕鹰爪虾和养殖南美白对虾肌肉中的主要营养成分及氨基酸组成进行了对比分析,并对两种原料在4±1°C贮藏过程中感官品质,pH、挥发性盐基氮(TVB-N)、K值、生物胺等生化指标,以及细菌总数、细菌菌相的变化进行了研究。结果表明,与养殖南美白对虾相比,海捕鹰爪虾肌肉中的蛋白质含量较高,水分含量较低,两种原料的氨基酸组成也有所差异。两种对虾在贮藏过程中,pH、TVB-N、K值和生物胺的变化趋势基本一致。与南美白对虾相比,鹰爪虾的初始细菌总数较低,在贮藏过程中细菌总数和细菌菌相的变化情况也有所不同。南美白对虾优势腐败菌为Pseudomonas(假单胞菌)和Aeromonas(气单胞菌),而鹰爪虾的优势腐败菌为Pseudomonas和Shewanella(希瓦氏菌)。两种原料在贮藏过程中感官品质都呈下降的趋势,但造成感官品质下降的原因有所不同,南美白对虾主要是由于细菌繁殖产生的不良气味和外观劣化造成感官上不被接受,而鹰爪虾主要是由于黑变,造成感官品质的急速下降。2.以从对虾腐败样品中分离到的11株细菌(7株革兰氏阴性菌,4株革兰氏阳性菌)为试验菌,通过滤纸片法,验证了壳聚糖、溶菌酶和Nisin等生物材料的抑菌效果。选用PA、EDTA和FH,采用三因素、三水平L9(34),进行正交试验,并进行方差分析,根据分析结果得到防黑变组分的最佳配比,并与抑菌物质复配,得到一种复合型防黑变保鲜剂。结果表明,该复合保鲜剂的最佳配比为:CH 0.5 g/L、PA 0.5 g/L、EDTA 0.5 g/L、FH 0.01g/L。海捕虾经复合保鲜剂处理后,在贮藏过程中细菌总数和TVB-N增加缓慢,黑变被有效抑制,货架期延长约1倍。通过核算,处理1Kg虾的成本仅为0.22元。3.研究了不同的熟制加工方式对虾仁质构的影响,并对传统煮制加工的工艺参数对虾仁失重率、色泽、质构和感官评价的影响进行了系统分析。结果表明,南美白对虾和鹰爪虾虾仁的最佳煮制工艺为:NaCl添加量2% (w/v),煮制时间分别为3-5 min和5-7 min,加工过程中应根据虾仁的大小规格对煮制时间进行适当调整,小规格的虾仁对应的煮制时间可适当减少。4.对虾仁煮制过程中微生物残留情况及生长特性进行了研究。从10批虾仁中分离到5株具有典型菌落形态的菌株,经传统的生理生化试验和16SrDNA方法鉴定,5株细菌均属于芽孢杆菌属。5株菌在低温条件下生长受到抑制,NaCl浓度在6%以上时可在一定程度上抑制其生长,中性及偏碱条件下生长良好,酸性条件下生长受到抑制。验证了不同的生物材料对5株芽孢杆菌的抑菌效果,最终确定Nisin作为即食虾仁产品的防腐保鲜剂,适宜浓度为0.5-1.0 g/L。5.采用间接测定法,即通过比色法测定芽孢内的特异性物质2,6-吡啶二羧酸(DPA),对芽孢进行检测。建立了吸光度对DPA浓度的线性回归方程:y=0.0027x+0.0052。该方程极显著(P < 0.01),校正决定系数R2Adj=0.9988,DPA在10-200μg/mL的范围内与吸光度呈良好的线性关系。5株芽孢杆菌芽孢的DPA泄漏率随加热温度的提高和加热时间的延长呈增加的趋势。在虾仁煮制加工的工艺条件下(100°C,5 min),5株芽孢杆菌的DPA泄漏率在21%-54%之间。60°C,20 min的预处理可以显著提高芽孢DPA的泄漏率,5株芽孢杆菌芽孢DPA泄漏率提高了18%-30%。6.对即食虾仁产品的生产工艺进行了进一步优化,针对微生物特性设置栅栏因子,并以水分含量、质构、色差、细菌总数、感官评定等指标在贮藏过程中的变化情况为依据,对产品的贮藏稳定性进行了研究。结果表明,通过设置栅栏因子,优化生产工艺,即食虾仁产品在4°C条件下保质期达到30天以上。贮藏过程中,产品的水分含量略有增加,硬度和弹性等质构指标及L值和C值等色差指标没有明显变化,细菌总数增长缓慢,感官评价良好。更多还原

【Abstract】 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.更多还原