真空包装淡腌青鱼品质和细菌类型及数量

在零售市场和生产企业抽取4批真空包装淡腌青鱼,对其感官、化学和细菌学品质特性进行分析,并对细菌类型和数量进行研究。结果显示,产品栅栏因子及强度存在差异,盐分含量6.68%~12.06%,平均值(9.36±2.2)%;水分活度值0.75~0.91,平均值0.82±0.07;pH值6.00~6.30,平均值6.20±0.13。栅栏因子种类和强度的不同决定产品品质的差异,感官评价均可接受,过氧化值均值为19.65±8.75 meq/kg,挥发性盐基氮均值为24.50±15.30 mg/100 g,菌落总数均值为4.45±1.15 cfu/g,大肠菌群均低于30 MPN/100 g。从4批淡腌青鱼样品分离到234株细菌,73.9%是革兰氏阳性细菌,其中36.3%是葡萄球菌,31.6%是链球菌,并出现少量微球菌和棒状杆菌;由需氧革兰氏阴性杆菌不动杆菌、摩氏杆菌和鞘氨醇单胞菌组成较小的细菌菌群约占总细菌群落的18.4%,显示水分活度、盐分含量和pH值等栅栏因子与产品细菌类型和数量呈一定相关性。     

青鱼背肉、腹肉和尾肉不同风味成分的比较

淡水鱼类不同部位肉的化学组成有较大差异,为了更深入地探究青鱼背肉、腹肉和尾肉风味差异,研究了青鱼(Mylopharyngodon piceu)不同部位(背肉、腹肉、尾肉)之间风味成分的异同,比较了青鱼3种部位肉水溶性滋味物质及挥发性成分的差异,为青鱼的水产加工工艺方法及加工装备研制等提供参考。使用高效液相技术和氨基酸分析仪研究了青鱼不同部位肉水溶性滋味物质,并采用电子舌技术对青鱼不同部位肉进行区别分析,使用顶空固相微萃取-气相色谱-质谱联用技术(HS-SPME-GC-MS)研究比较了青鱼不同部位肉的挥发性成分。结果显示:电子舌分析可以有效区分青鱼背肉、腹肉与尾肉之间的差别。青鱼3个部位肉滋味成分差异显著,青鱼腹肉总游离氨基酸含量显著高于背肉,而尾肉含量最低。K值一般用来评价水产品的新鲜度,定义为HxR(次黄嘌呤核苷)和Hx(次黄嘌呤)占ATP(三磷酸腺苷)所有关联化合物总量的百分含量,背肉的K值为5.01%,显著低于腹肉(10.04%)和尾肉(12.87%),说明利用K值比较鱼肉鲜度应注明取样部位。鱼肉EUC值结果表明腹肉呈味优于背肉,背肉优于尾肉。对青鱼肉气味贡献较大的物质有己醛、1-辛烯-3-醇、壬醛、正己醇、庚醛、(E)-2-辛烯醛、戊醛等。青鱼3个部位肉水溶性滋味成分差异显著,挥发性成分也有些许差异。青鱼腹肉与背肉风味优于尾肉,在研究青鱼风味与新鲜度时应注意区分青鱼背肉、腹肉与尾肉。     

不同贮藏条件对白市驿板鸭中亚硝酸盐含量的影响

[目的]研究不同贮藏条件对白市驿板鸭中亚硝酸盐含量的影响。[方法]比较了白市驿板鸭在自然通风、自然密封、冰箱直接放置和冰箱密封放置4种不同条件下贮藏时,其亚硝酸盐的含量随着贮藏时间的变化趋势。[结果]试验得出,在不同的贮藏条件下,白市驿板鸭中亚硝酸盐的含量随着贮藏时间的延长都呈下降的趋势;相同包装条件下,室温贮藏的板鸭中亚硝酸盐含量要比冰箱贮藏的低;相同温度下,密封贮藏的板鸭中亚硝酸盐含量比不密封的低。[结论]研究可为白市驿板鸭的科学制作和食用提供一定的理论依据。     

金属离子对蛋清蛋白质结构的影响研究

本文旨在探讨各种金属离子对腌制鸭蛋蛋清蛋白质结构的影响。研究发现:金属离子腌蛋后增加了蛋清蛋白质的β-折叠,分子展开而促进交联。但长时间金属离子的处理可导致蛋白质分子通过疏水作用部分簇集,使其表面疏水性下降。蛋清蛋白加热后α-螺旋减少、β-折叠比例增加,同时增加蛋白质表面疏水性,金属离子通过影响蛋清蛋白结构,促进蛋白质在加热过程中随机聚集,形成凝胶网络交联度降低,结构粗糙、空洞多、网络不均匀,从而影响蛋清凝胶结构特性。二价金属离子对蛋清蛋白质构象和蛋清凝胶微观结构的影响较一价离子更强,亦基本符合霍夫曼斯特离子序。     

腌制剂对脉动压腌制咸鸡蛋的影响

为丰富咸蛋品种,改善咸蛋风味,提高咸蛋的腌制速率,应用脉动压技术,以鸡蛋为原料,选取白酒、香辛料、柠檬酸为影响因素,通过单因素及正交试验,考察咸蛋腌制中蛋质量增加率、蛋清含盐率和蛋黄含盐率的变化,对腌制禽蛋工艺进行优化。结果表明：白酒和柠檬酸对盐分渗入有促进作用,而香辛料则阻碍了盐分的渗入,影响咸蛋综合评分的因素从高到低依次为香辛料、白酒、柠檬酸,且香辛料对咸蛋综合评分的影响显著,柠檬酸对蛋清含盐率的影响显著。在高压幅值140 kPa、脉动比2.5 min/5min饱和食盐溶液中腌制96 h,风味咸蛋腌制     

Prevalence and Characterization of Coagulase Positive Staphylococci Isolated from Salted Anchovy

A total of 100 salted anchovy samples were used to investigate the prevalence of S. aureus and other coagulase positive Staphylococci (CPS) as well as to determine the methicillin (MR) and antibiotic resistance (AR) profile, the presence of Panton-Valentine leukocidine (PVL) toxin gene (lukS/F-PV), slime factor properties (SFP), and the genotypic relatedness of the isolates. Agar disc diffusion assay (ADDA) and microdilution broth susceptibility test (MDBST) were applied to compare the specificity and sensitivity of the MR detection methods. A total of 41 CPS isolates were detected at the 10² and 10³ CFU/g levels in contrast to S. aureus. The 16S rRNA (genus specific) was detected in all the isolates in contrast to nuc (species-specific) and lukS/F-PV genes. A total of 16/41 isolates were found to be MR by using the three methods. Polymerase chain reaction (PCR) assay was a more sensitive and reliable method for the detection of MR isolates. The antibiotic resistance rates were 75.60, 73.17, 51.21, 31.70, 12.19, and 4.87% to penicillin, ampicillin, tetracycline, erythromycin, ciprofloxacin, and clindamycin, respectively. All the isolates were sensitive to gentamicin and vancomycin. The SFP were determined in all the isolates by using Congo Red agar, and 20 different genotypes were determined by using randomly amplified polymorphic DNA (RAPD)-PCR assay.     

Prevalence and Serotype Distribution of Listeria monocytogenes in Salted Anchovy,Raw Anchovy,and Raw Mussel Using IMS-Based Cultivation Technique and PCR

In the present study, a total of 150 samples including 50 salted anchovy, 50 raw anchovy, and 50 raw mussel samples collected from the retailers and small-scale producers in Samsun province from the Black Sea region of Turkey were analyzed; and 12% (6/50), 2% (1/50), and 2% (1/50) of the samples, respectively, were found to be contaminated with L. monocytogenes. According to the serotype distribution, six salted anchovy and one of the raw fish samples were contaminated with L. monocytogenes 1/2b (or 3b). In one raw mussel, both L. monocytogenes 1/2b (or 3b) and 4b (or 4d or 4e) serotypes were detected.     

Bacterial Contribution to Salted Anchovy (Engraulis anchoita Hubbs & Marinni, 1935) Ripening Process

The bacterial populations of the salted anchovy ripening process and its potential role on the development of the typical sensory characteristics of this product were studied. Salted anchovy samples were taken during the ripening process and submitted to microbiological analyses in order to monitor the evolution of bacterial groups. According to the results obtained, the ripening process was dominated by moderate halophilic bacteria. Moreover, many of the isolated strains showed proteolytic, lipolytic, and trimethylamine oxide (TMAO) reductase activities. These activities contribute to the development of the typical flavor of this product and to the increase of total volatile bases observed during ripening.     

Responses to fishmeal and soybean meal‐based diets by three kinds of larval carps of different food habits

A 60‐day trial was conducted in a recirculation system to determine the responses of herbivorous grass carp (Ctenopharyngodon idellus) (0.43 g), omnivorous gibel carp (Carassius auratus gibelio CAS III) (0.46 g) and carnivorous black carp (Mylopharyngodon piceus) (0.46 g) when fed with fishmeal (FM)‐ or soybean meal (SBM)‐based diets. Two isonitrogenous (380 g kg^?1 DM), isolipid (80 g kg^?1 DM), isocaloric (17.75 kJ g^?1) diets were formulated using FM and SBM as main protein sources. The results showed that weight gain (WG), feed efficiency (FE) and protein retention efficiency (PRE) in FM group were significantly higher than those in SBM group. Grass carp showed better utilization on SBM than other two species and presented higher WG, FE and PRE. When fed with SBM diet, intestinal chymotrypsin (CHY), lipase and trypsin (TRY) activities of gibel carp and black carp decreased while higher α‐amylase (α‐AMY) activity of grass carp increased. An enteritis‐like effect was observed in black carp and grass carp fed SBM diet. Intestine bacteria mainly belonged to Firmicutes in gibel carp and Proteobacteria in black carp. The dominant genera identified in three species were Cellulomonas, belonging to Actinobacteria. In conclusion, SBM decreased the growth of three carps. Grass carp was more adapted to plant protein.     

Effect of soybean meal replacement by cottonseed meal on growth,feed utilization and some blood physiological/biochemical indices of juvenile black carp,Mylopharyngodon piceus

A feeding trial was conducted to evaluate the effect of replacing soybean meal (SBM) with cottonseed meal (CSM) for juvenile black carp. The inclusion levels of CSM were 0 (control), 96.6, 193.3, 289.8 and 386.5 g kg^?1, in which 0, 25, 50, 75 and 100% of protein from SBM were replaced with that from CSM respectively. The results showed that up to 75% of SBM could be replaced by CSM without significant reduction in growth. The apparent digestibility coefficients of dry matter and protein, red blood cell and white blood cell count were significantly decreased with the increase in dietary CSM levels (P < 0.05). The activities of serum catalase (CAT), lysozyme (LSZ) and complement C3 were significantly lower than that of control group when dietary CSM level were increased to 386.5 g kg^?1, 96.6 g kg^?1 and 289.8 g kg^?1 or higher respectively. The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum were significantly higher than that of control group when dietary CSM levels were increased to 289.8 g kg^?1 or higher (P < 0.05). These results suggested that growth of black carp was not affected when CSM levels up to 289.8 g kg^?1; however, negative influence on immune and liver function was found when CSM levels up to 96.6 g kg^?1 and 289.8 g kg^?1 respectively.