水发海参真空冷冻干燥技术及冻干海参复水工艺的研究

为了提高冻干海参的品质,以水发海参为原料,研究了真空冷冻干燥过程中各技术要点对海参品质的影响及冻干海参复水工艺条件。结果表明:对于体长9~10cm,重35-40g的水发海参,-30t左右是比较理想的冻结温度。采用“程序降温”的冻干加热方式,能获得高品质的冻干海参制品。确定出冻干海参的高低温复水工艺,即先高温复水10分钟,再于4T纯净水中涨发120分钟,可以获得口感良好、个体饱满的复水海参。     

复合蛋白酶在即食海参加工中的应用

用复合蛋白酶处理盐渍海参,作为加工冻干即食海参的预处理样品,研究其酶处理最适工艺。试验结果表明,酶处理温度40℃,处理50 m in,水浸泡13 h,酶用量为肉重0.075%时,处理后的海参胶原蛋白溶解度(DD%)为(38.14±0.52)%,与水发海参接近[(39.34±0.47)%],口感达到最佳。从酶处理海参和盐渍海参的红外光谱分析可知,二者的营养成分无明显差异,达到生产冻干即食海参的要求。     

大黄鱼仔、稚、幼鱼发育阶段的脂肪酸组成及其变化

为了探讨真空冷冻干燥过程参数对冻干时间和能耗的影响，以墨西哥湾扇贝为研究对象，设计二次正交回归组合试验方案，采用SAS统计软件对试验数据进行回归分析，建立了真空冷冻干燥时间和能耗的二次多元回归模型，并对二次多元回归模型进行了F检验；利用降维法定性地分析了物料厚度、干燥室压强和加热板温度3个主要过程参数对真空冷冻干燥时间和能耗的影响。结果表明，物料厚度、干燥室压强和加热板温度对冻干时间和能耗影响显著，并呈二次函数规律变化，在本试验条件下影响的主次因素依次为：物料厚度、干燥室压强、加热板温度。对单位厚度冻干时间进行岭嵴分析，给出了在本试验因素取值范围内的冻干过程优化参数：物料厚度为9mm；干燥室压强为50Pa；加热板温度为39℃，优化的物料单位厚度冻干时间为0．41h。     

低场核磁共振技术在鱼用冻干疫苗保护剂筛选中的应用

为筛选适合鱼类冻干疫苗中使用的保护剂,采用低场核磁共振技术(LF-NMR)对冻干后不同保护剂中的水分分布和迁移规律进行了分析。根据水中氢质子的弛豫时间,可将保护剂中的残留水分为结合水、不易移动水和自由水3种形态。结果显示:冷冻干燥过程中二次干燥温度对甘露醇和蔗糖中残留水的分布有较大影响,随着温度从4℃升高到37℃,大部分自由水解吸而小部分转化为结合水。当冻干后的样品暴露在相对湿度43%和温度25℃的环境中时,大部分保护剂吸收水分,并将其固定为结合水,而甘露醇中的部分结合水则转变为自由水,并解吸到环境中。不同冻干保护剂中的水分分布和迁移并不相同,代表其具有不同的水分结合能力。该研究结果有助于鱼用冻干疫苗中保护剂的筛选和冻干工艺的优化,以便获得更加稳定的疫苗产品。     

海参微波冻干过程活性成分保存研究

针对海参传统干制技术周期长、复水困难、活性成分损失率大的问题,寻找一种合理的干制海参方法以有效保存海参中的活性成分,同时操作成本又较低.研究了不同干燥工艺对海参活性成分的影响规律,以及各种干燥方式的能耗和复水性,得出微波冷冻干燥可有效保存海参活性成分,其能耗较低,干燥周期较短.最后得出合理的微波冷冻干燥工艺参数:最佳物料表面温度上限设为60℃,最佳功率取2 W/g.能耗比常规冷冻干燥节约近50%.     

水产品真空冷冻干燥技术的研究现状与展望

随着生活水平的提高,人们对水产品品质提出了更高的要求,因此开发新的加工技术势在必行。冻干食品以其优良的营养品质,易流通、贮藏和方便食用,迎合了这一发展趋势。本文综述了水产品真空冷冻干燥过程中前处理工艺(切片处理、超声波处理、浸渍处理、涂膜处理等)、冻干工艺参数(预冻工艺参数、干燥条件等)、品质变化(感官、质构、营养、风味、滋味、复水性)和品质预测模型的研究现状,并重点探讨水产品真空冷冻干燥技术今后的研发趋势,为水产真空冷冻干燥制品的研究与应用提供参考。     

真空冷冻干燥金枪鱼的吸湿特性研究

采用两种冻结方法对金枪鱼进行真空冷冻干燥,绘制冻干曲线.并应用静态测试法,获得相应的等温吸湿线,从而对冻干金枪鱼吸附规律进行探讨.结果表明:在温度、相对湿度相同的条件下,快速冻结方法所得冻干制品的吸湿性较大.     

干海参加工过程中腌渍处理对品质的影响

腌渍是干海参加工过程中的重要环节,产品品质与腌渍方式密切相关。本实验以鲜活刺参(Apostichopus japonicus)为原料,按不同的腌渍工艺分别将其制成淡干、盐干和糖干海参,比较其在成品出成率、水发倍数、复水后干重率以及主要营养成分损失等方面的差异。结果表明,淡干、盐干和糖干海参的成品出成率分别为7.80%、9.43%和12.11%,盐渍和糖渍处理显著提高了干海参的成品出成率;3类干参的水发倍数分别为10.61、8.47和6.33,复水后干重率分别为70.39%、56.21%和35.88%,与淡干参相比,盐干和糖干海参的水发倍数和复水后干重率明显偏低(P0.01);淡干、盐干和糖干海参在整个加工过程中蛋白质损失率分别为11.35%、22.70%和31.03%,海参多糖损失率分别为12.66%、22.78%和31.64%,盐渍和糖渍处理造成蛋白质和海参多糖的大量损失,且糖渍比盐渍损失更大。本研究分析对比了不同类型干海参的质量差异,为海参加工工艺的选择和优化提供了参考。     

墨西哥湾扇贝的变压真空冷冻干燥的实验研究

文章是在前期实验研究基础上的后续。前期对墨西哥湾扇贝恒压法的冷冻干燥过程作了研究,得到优化的冻干参数。但对较复杂的冻干过程来说,用简单的固定板温和固定箱内压力所得到的参数,不可能对冻干的每一时刻都是最佳的。该文研究了由实验探索调压法对冻干时间的影响,以获得较优的冻干参数。结果表明,变压法的较优参数为高压60 Pa,低压10 Pa,调压时物料中心温度0℃。变压法与恒压法的优化实验相比,冻干时间可以缩短10%左右,优化后可以缩短约20%。     

无公害食品 水发水产品

1 范围 本标准规定了无公害食品水发水产品的要求、实验方法、检验规则、标志、包装、运输与贮存。本标准适用于干制品水发的水产品（包括水发海参、水发鱿鱼、水发墨鱼、水发干贝、水发鱼翅等），水浸泡销售的解冻水产品（解冻虾仁、解冻银鱼等），以及浸泡销售的鲜水产品（鲜墨鱼仔、鲜小鱿鱼等）；其他类似水产品可参照执行。     

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.     

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).     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven,Hemitripterus americanus

The sea raven, Hemitripterus americanus, is a sit-and-wait, low metabolic rate, marine teleost. The objective of this study was to determine i) whether cortisol implantation (50 mg. kg^-1) for 7 days altered hepatocyte metabolism, and hepatocyte responsiveness to epinephrine, glucagon and insulin, and ii) whether 8 weeks of food-deprivation modified the above response. Cortisol implantation significantly increased hepatocyte total glucose production and oxidation from alanine compared to the sham group. There was no cortisol effect on glycogen breakdown, suggesting that the activation of other pathways, including gluconeogenesis, are required to account for the increased glucose production. Epinephrine-mediated (10^-5M) glycogen breakdown and insulin-mediated (10^-8M) total glucose production were enhanced in hepatocytes of cortisol implanted sea ravens, but there were no change in any glucagon (10^-7M) effects. The enhanced glycogen breakdown in the absence of similar increases in total glucose production with epinephrine indicates mobilization of carbohydrate reserves for endogenous use by the liver. Food-deprivation for 8 weeks significantly decreased condition factor, plasma cortisol concentration and liver glycogen content in the sea raven, but had no effect on plasma glucose concentration. Hepatocyte total glucose production and flux rates from alanine increased significantly with food-deprivation. Moreover, food-deprivation increased responsiveness of total hepatocyte glucose production to the actions of glucagon and insulin, but not to epinephrine; none of these effects were modified by cortisol implantation. Our results indicate that cortisol in the sea raven exerts both a direct and an indirect or permissive effect on hepatocyte metabolism by modifying hepatocyte responsiveness to epinephrine and insulin stimulation. Cortisol implantation did not modify the effects of glucagon or food-deprivation in this species.     

Simulation and quantification of enrichment and retention processes in the southern Benguela upwelling ecosystem

Important environmental processes for the survival and recruitment of early life stages of pelagic fishes have been synthesized through Bakun's fundamental triad as enrichment, concentration and retention processes (A. Bakun, 1996, Patterns in the Ocean. Ocean Processes and Marine Population Dynamics. San Diego, CA, USA: University of California Sea Grant). This conceptual framework states that from favourable spawning habitats, eggs and larvae would be transported to and/or retained in places where food originating from enrichment areas would be concentrated. We propose a method for quantifying two of the triad processes, enrichment and retention, based on the Lagrangian tracking of particles transported within water velocity fields generated by a three‐dimensional hydrodynamic model. We apply this method to the southern Benguela upwelling ecosystem, constructing putative maps of enrichment and retention. We comment on these maps regarding main features of the circulation in the region, and investigate seasonal variability of the processes. We finally discuss the results in relation to available knowledge on the reproductive strategies of two pelagic clupeoid species abundant in the southern Benguela, anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Our approach is intended to be sufficiently generic so as to allow its application to other upwelling systems.     

Effects of capture,loading density and transport stress on the mortality,physiological responses,bacterial density and growth of rohu <Emphasis Type="Italic">Labeo</Emphasis><Emphasis Type="Italic"> rohita</Emphasis> fingerlings

This study evaluated the effects of three levels of loading density (200, 300 and 400 g L⁻¹) and four levels of duration (1, 3, 6 and 9 h) on the mortality, plasma cortisol and chloride levels and growth of rohu Labeo rohita fingerlings in a transport simulation. While total immediate mortality was low (4–12%), delayed mortality was high (27–49%). Initial capture and handling were found to constitute the most stressful phase as indicated by elevated plasma cortisol. The levels of cortisol continued to rise at 6 and 9 h after transport, with the highest level observed at 9 h after transport. The level of plasma chloride fell after transport across all density levels and treatment durations. Specific growth rate (SGR, %/day) and total bacterial density (cfu/g) were not different between and within treatments, and between treatments and the controls. This study demonstrates that transport has a profound effect on the stress responses of rohu fingerlings. Although the level of immediate mortality was low, the higher level of delayed mortality has serious implications in terms of production inefficiency for grow-out farmers.     

The effects of introduced tilapias on native biodiversity

• 1. The common name ‘tilapia’ refers to a group of tropical freshwater fish in the family Cichlidae (Oreochromis, Tilapia, and Sarotherodon spp.) that are indigenous to Africa and the southwestern Middle East. Since the 1930s, tilapias have been intentionally dispersed worldwide for the biological control of aquatic weeds and insects, as baitfish for certain capture fisheries, for aquaria, and as a food fish. They have most recently been promoted as an important source of protein that could provide food security for developing countries without the environmental problems associated with terrestrial agriculture. In addition, market demand for tilapia in developed countries such as the United States is growing rapidly.
• 2. Tilapias are well‐suited to aquaculture because they are highly prolific and tolerant to a range of environmental conditions. They have come to be known as the ‘aquatic chicken’ because of their potential as an affordable, high‐yield source of protein that can be easily raised in a range of environments — from subsistence or ‘backyard’ units to intensive fish hatcheries. In some countries, particularly in Asia, nearly all of the introduced tilapias produced are consumed domestically; tilapias have contributed to basic food security for such societies.
• 3. This review indicates that tilapia species are highly invasive and exist under feral conditions in every nation in which they have been cultured or introduced. Thus, the authors have concluded that, despite potential or observed benefits to human society, tilapia aquaculture and open‐water introductions cannot continue unchecked without further exacerbating damage to native fish species and biodiversity. Recommendations include restricting tilapia culture to carefully managed, contained ponds, although exclusion is preferred when it is feasible. Research into culture of indigenous species is also recommended.

Copyright © 2005 John Wiley & Sons, Ltd.