即食半干虾仁加工技术研究

以凡纳滨对虾（Litopenaeus vannamei）为试验原料,探索半干即食虾仁的加工技术。对蒸煮时间及顺序、调味配方、干制方式及杀菌条件等制作工艺关键步骤进行了研究,制作出风味浓郁、口感良好的半干即食虾仁。最佳的工艺条件为先蒸煮后调味,蒸煮时间为5min,通过正交试验筛选调味配方为1L水需加盐50．0g、糖50．0g、柠檬酸2．0g、味精5．0g,二段干燥,先后于50℃和60cC各烘干1h,80～85℃杀菌处理30rain,此条件下可以较好地保持产品的品质和风味。该研究为对虾的开发利用及提高产品附加值提供了新途径。     

即食型麻辣鮰鱼条加工工艺研究

以鲜活斑点叉尾鮰为主要原料,以成品感官品质为指标,通过单因素及正交试验的方法对即食型麻辣鮰鱼条的加工工艺进行研究。结果表明:该产品最佳腌料配方为:食盐1.5%、白酒0.8%、白胡椒0.3%、生姜0.5%;最佳调味料配方为味精0.2%、I+G 0.01%、菜籽油5.5%、食盐0.8%、白砂糖3.0%、花椒粉2.0%、辣椒粉3.0%。通过两次烘烤,分别为60℃条件下烘制2h和160℃条件下烘烤10min。按此工艺生产的即食型麻辣鮰鱼条具有独特的风味与口感。     

鲟鱼皮软包装冷冻调理食品加工工艺

试验以鲟鱼皮为原料,通过试验确定了鲟鱼皮软包装冷冻调理食品的脱腥工艺、调料配方、灭菌条件,以及适于工业化生产的配方与工艺条件。筛选得出最佳脱腥工艺条件:碳酸氢钠1%,氯化钠1.8%,乙醇5%;最佳调味料配方:食盐2.5%,味精1.5%,白砂糖2.0%,黄酒2.5%,芝麻油3.0%;最佳灭菌条件:温度100℃,时间15 m in。     

茄汁罗非鱼软包装罐头加工技术研究

主要探讨茄汁罗非鱼软包装罐头的加工技术,着重就茄汁罗非鱼腌制、油炸条件、调味配方的筛选和杀菌条件进行研究。试验结果表明：茄汁罗非鱼的最佳腌制方法为干法腌制,盐用量为5．5%,腌渍时间为5～6 h；最适油炸条件为180～200℃时,油炸3～5 min。通过多因素实验筛选确定调味茄汁的最佳配方[每100 mL水中添加量(g)计]为：蕃茄汁85．0、白糖9．0、白醋1．0、胡椒粉0．4、味精0．4、黄酒8．0、香料水8．0 g,杀菌公式为10 min-30 min-15 min/118℃。     

即食菲律宾蛤仔休闲食品加工工艺研究

为研究即食菲律宾蛤仔休闲食品加工工艺,本文探讨了不同脱腥、腌渍、护色及干燥工艺对蛤制品口感风味、水分含量及产品质构特性的影响,采用单因素和正交优化组合试验确定了菲律宾蛤仔休闲食品的最佳工艺条件。其中,脱腥工艺参数:2.0%茉莉花+2.0%姜汁,时间80 min;腌渍工艺参数:食盐5%、味精2.0%、白砂糖8%,时间4 h;护色工艺参数:D-异抗坏血酸钠0.10%,时间1 h;干燥工艺参数:温度75℃,时间3 h。在该工艺条件下生产的即食菲律宾蛤仔制品,风味独特,口感极佳。     

巴氏杀菌和超高压杀菌对即食小龙虾货架期的影响

为开发基于小龙虾(学名克氏原螯虾,Procambarus clarkii)的深加工产品,以质构、菌落总数、挥发性盐基氮(TVB-N)、pH、色差为评价指标,探讨两种不同杀菌方式(巴氏杀菌80℃/15 min;超高压杀菌300 MPa/15 min)对4℃贮藏温度下真空包装即食小龙虾品质的影响。研究显示:巴氏杀菌组的菌落总数和TVB-N分别在第13天(5.5 log(CFU/g))和第14天(20.94 mg/100 g)超过国家水产限量标准(分别为5.0 log(CFU/g)和20 mg/100 g),而超高压杀菌组,分别在第15天(5.15 log(CFU/g))和第16天(21.26 mg/100 g)超过国家水产限量标准;且超高压杀菌组即食小龙虾硬度(1 358.33 g)、粘着性(987.66)、咀嚼性(840.84)均显著(P0.05)高于巴氏杀菌组(分别为1 188.42 g、769.00和551.07);两组即食小龙虾pH均呈先下降后上升趋势,且无显著性差异(P0.05);此外,经超高压杀菌处理的即食小龙虾色泽也略优于巴氏杀菌组,但无显著性差异(P0.05)。结果表明:在4℃的贮藏条件下,超高压杀菌处理的即食小龙虾货架期为14 d,相比80℃巴氏杀菌处理组,延长了约2 d的货架期,但两种杀菌方式处理的即食小龙虾产品的理化性质和菌落总数差距不大。     

两种杀菌方式对即食小龙虾理化性质及挥发性风味物质的影响

为了开发基于小龙虾的深加工产品,本试验以即食小龙虾为对象,研究两种杀菌方式对小龙虾氨基酸营养品质、质构特性、感官评价等理化性质的影响,并对其挥发性风味物质进行顶空固相微萃取气相色谱质谱(HS-SPME-GC-MS)联用分析。结果显示:巴氏杀菌处理的即食小龙虾氨基酸营养品质、质构特性及感官质量均优于高温高压杀菌组,更能迎合消费者的口味;巴氏杀菌和高温高压杀菌的即食小龙虾分别检测出41和44种挥发性风味物质;巴氏杀菌处理的即食小龙虾的醇类、醚类和酯类物质显著高于(P0.05)高温高压杀菌组,这可能是两者风味差异的主要原因。总之,采用巴氏杀菌处理的即食小龙虾品质更好,营养丰富,肉质鲜嫩,香味浓郁。     

调味河鲀休闲制品工艺研究

以河豚鱼肉为原料,开发即食调味河豚鱼片。采用色泽、口感、气味和组织形态的感官评分作为评价指标,在糖用量、盐用量、酱油用量3个单因素试验的基础上,采用响应面法优化调味制备工艺;在最佳工艺制备条件下,以感官分值和质构特性为评价指标确定满足商业无菌要求的最佳杀菌时间。结果显示:在糖用量6.7%、盐用量4.0%、酱油用量4.2%、用水煮香料液补至100%的条件下,预测感官分值高达8.15,感官评分结果为8.40,与预测值接近;确定最佳杀菌时间是15 min。研究表明:即食调味河豚鱼片的制备工艺可行,并可为其他水产制品的深加工提供参考。     

接种发酵糟鱼的杀菌工艺

为了探究接种发酵糟鱼的杀菌工艺,实验以草鱼作为原料,分析了干燥程度、杀菌条件等关键工艺参数对接种发酵糟鱼理化特性、感官特性等品质的影响,以及保藏期间产品食用安全品质的变化。结果显示,当糟制前鱼块干燥至水分含量分别为63.48%、55.37%和47.76%时,糟制后鱼块的水分活度值(Aw)分别为0.86、0.82和0.78。在杀菌强度F=5 min时,90和95℃杀菌处理后,产品出现胀袋现象;当F≥6.5 min时,产品均达到商业无菌状态,并且产品的a*值随杀菌温度升高而显著增大,L*值、b*值和剪切力变化不显著,杀菌温度为95℃时具有最高的感官评分84.9。在120 d贮藏期内,4和25℃贮藏的产品均未检出肠杆菌,且pH值和Aw值变化不大,其中4℃下贮藏的即食糟鱼具有更佳的感官品质。因此,接种糟鱼的最佳杀菌工艺为安全杀菌强度F=6.5 min、温度95℃、杀菌时间17.4 min,产品贮藏期可达120 d。研究表明,合理的干燥程度、杀菌条件以及保藏温度等关键工艺能够有效提高糟鱼的保藏品质。本研究对于促进草鱼的加工利用,提高杀菌即食水产品的品质具有重要的实践意义。     

真空微波膨化即食海带脆片工艺研究

为了研究新型即食海带脆片产品的加工工艺,采用盐渍海带为原料,对真空预干燥的海带进行微波膨化加工工艺优化。结果表明:海带规格(长×宽)为2.0 cm×0.4 cm,经3%柠檬酸溶液浸泡脱腥处理,调味液浸泡30 min后沥干,60℃下真空干燥至海带原料水分质量分数为20%,微波膨化功率为320 W,微波工作/间歇时间为10 s/10 s,按照这样的加工工艺可制得营养即食海带脆片产品。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.