Assessment of Some Heavy Metals in Fresh Fish (Oreochromis aureus): Case of Toho Lake in South Eastern Benin, West Africa

The protection of aquatic ecosystems is of great importance to maintain the biological balance necessary to secure healthy foods therein imbedded. Toho Lake, located to the south east of Benin, is threatened by pollution emanating from anthropogenic activities with the use of chemical fertilizers, effluent of domestic waste, particularly human and animal excrement with neighbourhood effluents. This study aimed at assessing some heavy metals in fresh fish (Oreochromis aureus) of Toho Lake in order to secure healthy food for the population and protect the ecosystem. Samples of water and fishes were collected and analyzed by HACH DR 3900 after treatment. Results revealed a mean oxygenation of water (4.95 mgo2/l), Biochemical Oxygen Demand (21.5 mgo2/l), Chemical oxygen Demand (149, 39 mg/l) with the nitrogen in Nitrate (NO3: 0.18 mg/l), ammonium nitrate (N-N: 0.47 mg/l), and phosphorous (2.06 mg/l) to be very high. The highest contents of heavy metals obtained in the fresh fish were cadmium (32.25 mg/kg), copper (115 mg/kg), lead (8.25 mg/kg), and zinc (90.75 mg/kg) and revealed that the fishes of Toho lake were polluted. The finding allowed us to conclude that the pollution of the lake and the fish carnage are due to anthropogenic pollution through chemicals spilling. Some protection methods of the lake and ecosystem are proposed in order to keep the fish safe and protect the well-being of the population.

Comparative Analysis of Disparity in Demand for Fresh Fish between Rural and Urban Households in Cameroon

The past decades have exhibited changes in the consumption of fresh fish. In developing countries, factors affecting fish consumption are different between urban and rural households. This study comparatively analyses the disparity in demand for fresh fish between rural and urban households in Cameroon. Using random sampling, data on the weekly consumption of fresh fish were collected between April and May 2015;30 households lived in rural localities while 30 lived in urban areas of Buea Municipality. Consumer’s income, the price of fresh fish, family size, gender and age of consumers represented parameters of interest. These were analyzed using the independent sample t-test. Results revealed that the availability, the income level and price affected fish consumption of rural dwellers while price, taste, income and affordability determined the consumption patterns of urban dwellers. The study equally revealed that the higher the price of fresh fish, the higher the demand for its closed substitutes and the higher the size of the household, the higher the quantity demanded. Gender, education and marital status did not affect the quantity demanded;family size and age negatively influenced consumers’ decision to buy while consumers’ income and price of fresh fish positively influenced consumers’ weekly and monthly expenditure on fresh fish. The study proposes that more information be provided to consumers regarding the numerous nutritional benefits of fresh fish for both rural and urban dwellers. Also, policy makers and marketers need to improve the availability of fresh fish in rural and semi-urban settings.

Biogenic amines in fresh fish and fishery products and emerging control

Occurrence of biogenic amines in fresh fish and fishery products constitute a significant safety concern.Ingestion of histamine is identified as the causative agent of several food poisoning incidences on an annual basis.In addition,cadaverine,putrescine and tyramine have been recognized as potentiators of histamine poisoning.Accumulation of biogenic amines in fresh fish and fishery products has been mainly attributed to growth of bacteria possessing amino acid decarboxylase activity,which is facilitated by lack of hygienic conditions and strict temperature control during their storage.To this end,the effectiveness of traditional and modern approaches to control biogenic amine accumulation has been in the epicenter of intensive study.The aim of the present review article is to update and integrate current knowledge regarding the biogenic amine content of fresh fish and fishery products as well as the capacity of traditional and emerging control strategies.

Development,Characterization and Application of a Three-Layer Intelligent pH-Sensing Indicator Based on Bromocresol Green(BCG)for Monitoring Fish Freshness

As a novel food quality monitoring technology,intelligent freshness indicator has received wide attention in recent years.However,its poor safety and stability are the main problems hindering its practical application.Hence a new pH-sensing indicator based on bromocresol green(BCG)was developed in this study for nondestructive and real-time monitoring the freshness of marine fishes.The indicator was designed with a three-layer structure,using the polytetrafluoroethylene(PTFE)membrane with high hydrophobicity and air permeability as the inner layer to isolate the moisture in the package,BCG-coated filter paper as the colorchanging layer to indicate the freshness of fish,and a transparent unidirectional permeable(TUP)membrane with moisture resistance as the out layer to isolate the moisture in the environment.This contributed to weaken the influence of humidity and prevent dye migration,so as to improve the accuracy and safety of the indicator.Therefore,a highly sensitive and distinguished color variation response to trimethylamine(TMA)standard solution with different concentrations was observed on the indicator.Additionally,the indicator showed a high color stability at different storage temperatures up to 14 days with total color differences(ΔE)less than 5.0.The indicator presented visible color variations from yellow to green then eventually to blue when applied to monitor the freshness of sea bass and salmon stored at 4℃,implying that fish was spoiled.Meanwhile,indicatorsΔE value was significantly positively correlated with total volatile basic nitrogen(TVB-N)and total viable count(TVC)in sea bass and salmon samples.Thus,the pH-sensing indicator can be applied as a cost-effective and promising intelligent indicator for monitoring fish freshness.

Developing a Machine Vision System Equipped with UV Light to Predict Fish Freshness Based on Fish-Surface Color

This study assessed the feasibility of developing a machine vision system equipped with ultraviolet (UV) light, using changes in fish-surface color to predict aerobic plate count (APC, a standard freshness indicator) during storage. The APC values were tested and images of the fish surface were taken when fish were stored at room temperature. Then, images’ color-space conversion among RGB, HSV, and L*a*b* color spaces was carried out and analyzed. The results revealed that a* and b* values from the UV-light image decreased linearly during storage. A further regression analysis of these two parameters with APC value demonstrated a good exponential relationship between the a* value and the APC value (R2 = 0.97), followed by the b* (R2 = 0.85). Therefore, our results suggest that the change in color of the fish surface under UV light can be used to assess fish freshness during storage.

Determination of the Contents of EPA and DHA and Lipid Constituents in Main Fresh Water Fishes in China

In this study the molecular formula and structure of lipid constituents of silver carp and bighead carp in middle reaches of Yangtze River were determined by gas chromatography-mass spectrometry. The position of double bounds was identified by the method of double bounds chemical localization. These carps are proved to contain eicosapantaenoic acid (EPA) and decosahexenoic acid (DHA). The contents of EPA and DHA, which were determined by gas chromatography, in silver carp and bighead carp were approximately the same as in tuna and salmon. The contents of EPA and DHA in 100 g wet sample were 0. 187 g, 0. 229 g and 0. 246 g, 0. 325 g respectively, but the cholesterol contents in silver carp and bighead carp were much lower than in tuna and salmon.

Analyses of Genetic Diversities in Chinese Fresh-water Fishes

A wealth of literature has been published in the studies of Chinese fresh-water fish chromosomes within recent years.In this paper,we review the inter-and intraspecific genetic diversities found in Chinese fresh-water fishes,and explore the characteristics and mechanisms that underline these diversities and variations. We also propose the hypothesis how the genetic diversities had evolved in the fresh-water fishes.

Are Midwestern fish retailers willing to pay more for regionally grown fresh-on-ice fish?

The fish and seafood market in the Midwestern region of the United States is currently dominated by frozen products. Fish producers in the region may be able to market their products as fresh, regionally grown and farmed fish. Fish producers may be able to supply fresh fish products that have not been previously frozen but preserved fresh with ice. The study examined retailers’ willingness to pay more for Midwestern fresh fish adopting the literature on consumers’ willingness to pay for market services or products, assuming that retailers understand their customers, and that they are able to add any premiums paid for to their retail prices. The overall probability of retailers paying more for regionally grown fresh-on-ice fish is low though consistency in supply and sourcing out of state positively affected the probability to pay more. In spite of these positive factors on willingness to pay more for Midwestern fresh-on-ice fish, Midwestern fish producers would probably remain non-competitive in the fresh-on-ice fish market in the short and medium term, and should continue to focus on the live market.

Effect of Digested Sewage Sludge on the Ventilation and Coughing Rates of Two Fresh Water Fish

Addition of digested sewage sludge at concentrations of 2% and 10% (v/v) to the water increased coughing rate in big head and tilapia (P<0.05). Ventilation rate was significantly decreased (P<0.05) in big head and tilapia at sludge concentrations of 6% and 2% (v/v)respectively. Copper (Cu), cadmium (Cd) and zinc (Zn) are trace metals which are commonly found in sludge. Cu caused a significant increase (P<0.05) in coughing rate in both tilapia and big head at concentrations of 0.3 and 0.2 μg/ml respectively. Zn caused significant increase (P<0.05) in coughing rate only in big head at 2 μg/ml. Neither fish responded to Cd of up to 2μg/ml in the water. However, when the levels of these trace metals in the digested sludge were measured, they were below that which can cause significant changes in the respiratory movements. Therefore, the changes in ventilation and coughing rates after addition of sludge may be due to the presence of substances other than these metals. The results of this experiment provides a guideline to control the level of sludge that can be used in rearing these fresh water fish in ponds

DDT and Its Metabolites in Fresh Water Fish Samples

Twenty two fresh water fish samples namely Puntius sarana （Shawrputi）, Cyprinus carpio （Karp）, Oreochromis niloticos （Telapia）, Channa punctatus （Taki）, Wallogonia attu （Boal）, Eutropiichthys vacha （Bacha）, Macrognathus aculiatus （Baim）, Ailia coila （Kajoli）, Mystus cavasisus（Gulsa）, Ompok pabda （Pabdha）, Corica soborna （Kachki）, Mystus vittatus （Tengra）, Glossogobius giuris （Baila）, Macrobrachium malcolmsli （Chingri）, Amblypharyngodon microlepis （Mola）, Anabas testudineus （Koi）, Macrognathus aculiatus （Baim）, Channa striatus （Shole）, Heteropnueste fossilis （Shing）, Puntius sophore （Small Puti） and Pseudambassis ranga （Telapia） were collected from two rivers and one cultured fish pond. The samples were extracted by QuEChERS method, cleaned up with conc. H2SO4 treatment and cleaned extracts were analyzed by GC-ECD. Small size cultured rui fish sample which did show detectable amount of DDT and its metabohtes was used for the recovery experiments. Percent recovery was found to be in the range of 70%-113%. Amount of total DDTs were found to be 54.34, 48.81, 62.09, 54.72,78.81, 60.07, 47.0, 42.7, 26.31, 10.36, 25.32, 12.96, 20.10, 12.78, 17.65, and 4.71, 8.58, 11.3 and 19.01 ng/g in gulsa, pabhda, baila, bacha, baim, small purl, tengra, chanda, kachki, boal, taki, chingri, mola, shole, shing, koi, swarpurl, karp and telapia fish samples, respectively. However, the residual amounts of DDTs in all the fish samples were below maximum residue limit （MRL of DDTs in fish 5.0 mg/kg） according to Codex Alimentarius Commission. The ratios of 4,4＇-DDT/DDTs were in the range of 0.03-0.44 which indicated that exposure to DDT is not due to recent use.

Effect of Fertilizer Diammonium Phosphate on Liver,Kidney and Muscle 5-Nucleotidase Activity of Fresh Water Teleost Fish Clarias batrachus

The toxic effect of fertilizer Diammonium phosphate resulted in alterations of 5'-Nucleotidase activity of tissues liver, kidney and muscles offish C. batrachus at varying intervals and exposures. Alterations in 5'-Nuclcotidase activity of body organs gave an idea of the toxicity caused by the fertilizer. Thus the enzyme 5'-Nucleotidase can be used to monitor the pollution in aquatic ecosystem.

配合饲料和冰鲜鱼对大口黑鲈肌肉中氨基酸、脂肪酸的组成和含量以及血清生化指标的影响

为缓解因大量投喂冰鲜鱼造成的大口黑鲈养殖水体污染、病害频发和生产效益降低等问题,加快推进优质配合饲料的开发,开展投喂配合饲料和冰鲜鱼对大口黑鲈营养价值和健康状况影响的研究至关重要。为此,本研究将360尾大口黑鲈分为3个试验组,分别投喂配合饲料、冰鲜鱼和混合饲料(配合饲料和冰鲜鱼的质量各占饲料总质量的50%),在饲喂90 d后对3组大口黑鲈肌肉中矿物元素含量、氨基酸的组成和含量、脂肪酸的组成和含量以及血清生化指标进行分析。结果表明,配合饲料组大口黑鲈肌肉中的Na、Ca、Zn含量显著高于冰鲜鱼组(P<0.05)。与配合饲料组和混合饲料组相比,冰鲜鱼组大口黑鲈肌肉中必需氨基酸总量占氨基酸总量的百分比以及必需氨基酸总量占非必需氨基酸总量的百分比更高。冰鲜鱼组大口黑鲈肌肉中各必需氨基酸的氨基酸评分和化学评分以及必需氨基酸指数均高于配合饲料组。配合饲料组大口黑鲈肌肉中饱和脂肪酸总量显著高于混合饲料组和冰鲜鱼组(P<0.05),但冰鲜鱼组的多不饱和脂肪酸(PUFA)总量、二十碳五烯酸含量和二十二碳六烯酸含量显著高于配合饲料组(P<0.05);与配合饲料组相比,冰鲜鱼组的n-6 PUFA含量更低,n-3 PUFA含量更高(P<0.05),并且脂肪酸品质更优。冰鲜鱼组和混合饲料组血清总蛋白质含量和碱性磷酸酶活性显著高于配合饲料组(P<0.05)。此外,冰鲜鱼组大口黑鲈血清中葡萄糖含量和谷草转氨酶活性最低(P<0.05)。因此,在本研究条件下,配合饲料影响大口黑鲈肌肉的营养价值和肝脏健康,建议参考冰鲜鱼的营养组成,进一步优化配合饲料配方。

两种投喂模式对中华绒螯蟹生长性能及可食部位风味品质的影响

为研究不同投喂模式对中华绒螯蟹生长性能及可食部位风味品质的影响,设置全程投喂配合饲料(A)和前期投喂配合饲料+后期投喂冰鲜鱼(B)两种投喂模式开展养殖试验。每组设置3个重复,每个重复雄蟹和雌蟹各15只。养殖试验结束后测定生长性能,肌肉、肝胰腺和性腺相关品质指标以及肝胰腺和性腺的挥发性物质含量。结果表明:两种投喂模式对中华绒螯蟹肝胰腺指数、肥满度及附肢肌肉的硬度、内聚性、弹性、剪切力均无显著影响(P>0.05)。B组的雄蟹性腺指数以及雌蟹的增重率、特定生长率显著高于A组(P<0.05)。B组的雌蟹生长性能优于A组(P<0.05),同样地,B组雄蟹肝胰腺和性腺色泽、肌肉胶原蛋白含量也优于A组(P<0.05),且B组的中华绒螯蟹具有更好的风味(P<0.05)。综上所述,前期投喂配合饲料而后期投喂冰鲜鱼的饵料模式对中华绒螯蟹的育肥及风味品质具有更好的效果。因此,后续对于配合饲料的开发建议着重于呈味物质、促胶原蛋白生成和育肥功能饲料的开发方面。

不同饵料对子一代中华鲟产后亲鱼康复效果的影响

研究旨在通过投喂不同饵料对中华鲟(Acipenser sinensis Gary,1835)子一代产后亲鱼的生长性能、血清抗氧化能力、营养物质代谢、肝功能和免疫指标的影响,探究不同饵料对子一代中华鲟产后亲鱼的康复效果。挑选18尾参与2022年繁育的中华鲟子一代亲鱼[平均初始体重为(80.64±9.80)kg],随机分为3组,分别采用投喂配合饲料、冰鲜鱼及配合饲料和冰鲜鱼早晚轮流混合投喂的方式喂养12周。结果表明,配合饲料和冰鲜鱼混合投喂可显著提高子一代中华鲟产后亲鱼的增重率(WGR)、体长增长率(LGR)和胸围增长率(CGR)(P<0.05);在血清抗氧化能力方面,混合投喂组和冰鲜鱼组的子一代中华鲟产后亲鱼血清过氧化氢酶(CAT)、超氧化物歧化酶(SOD)活性显著高于投喂配合饲料组(P<0.05);在营养物质代谢方面,相比于投喂配合饲料,投喂冰鲜鱼组的子一代中华鲟产后亲鱼血清甘油三酯(TG)和总胆固醇(T-CHO)含量显著升高(P<0.05),配合饲料组子一代中华鲟产后亲鱼血清总蛋白(TP)含量显著低于混合投喂组和冰鲜鱼组(P<0.05);在血清肝功能和免疫指标方面,混合投喂组子一代中华鲟产后亲鱼血清丙氨酸氨基转移酶(ALT)和天冬氨酸氨基转移酶(AST)活性显著低于配合饲料组(P<0.05),而碱性磷酸酶(ALP)活性及血钙(Ca2+)和血磷(P3+)含量显著高于配合饲料组(P<0.05)。在试验结束后15个月追踪研究其性腺发育激素水平,配合饲料组子一代中华鲟产后亲鱼血清雌二醇(E2)含量显著低于其他组(P<0.05)。综上表明,在试验条件下,对子一代中华鲟产后亲鱼早上投喂配合饲料、傍晚投喂冰鲜鱼,两种饵料混合投喂能够加强对营养物质的吸收,提高其生长性能、繁殖性能,并有效增强血清抗氧化免疫酶活性,提高免疫力和机体健康水平,促进其快速产后恢复,为中华鲟保种保育工作打下基础,对中华鲟种质资源的保护具有重要意义。

基于互补仓的轴辐式网络下生鲜农产品配送研究

轴辐式网络因高灵活性和快速反应能力在现代快递行业中已被普遍使用,而其中各枢纽节点也是降低物流供应链环节相关成本的重心所在。当前生鲜农产品因易腐败性和新鲜度极度依赖冷链运输,每次配送不可避免地会造成部分商品损毁而无法销售食用。文中着重研究将轴辐式网络与生鲜农产品的配送相结合,并在中途节点间设立互补仓,利用鱼群算法确定各互补仓的最佳选址地点,从而尽可能降低货损率以及物流成本,以期为生鲜农产品的配送提供新的解决方案。

溶蚀型海洋防污涂料制备及其性能

目的合成具有溶蚀性能的丙烯酸基体树脂,用该树脂制备中期效短期效溶蚀型海洋防污涂料。方法自由基聚合法合成具有溶蚀性能的丙烯酸基体树脂,用该基体树脂配以市场价格较便宜性价比较高的有机类防污剂代森锌、吡啶硫酮锌、敌草隆等,颜填料,助剂等制备溶蚀型海洋防污涂料。通过实海挂板试验、耐淡水浸泡测试、涂层微观样貌对涂层进行表征。结果丙烯酸基体树脂聚合物的数均分子量控制在25000左右较为合适,即聚合反应温度控制在110℃,引发剂用量为4份时较为合适。羧酸单体的含量为25%~30%时,基体树脂具有较好的溶蚀性能。制备的溶蚀型防污涂料经24个月实海挂板试验验证,具有优异的防污期效,经过12个月淡水浸泡,涂层不起泡、不脱落。防污涂层表面微观样貌表征,基体树脂的溶蚀性能,防污剂溶出后,涂层表面粗糙度增大,表面留有孔洞。结论该溶蚀型防污涂料具有优异的防污性能,能够防止海洋附着生物对船底和其他海洋设施的污损,可适用于中小型渔船对短期效海洋污损防护需求。

1例华支睾吸虫病患者及当地淡水鱼华支睾吸虫感染情况调查

目的 了解一例华支睾吸虫病患者镜检特征和qPCR检测结果以及当地淡水鱼华支睾吸虫感染现况。方法 镜检和qPCR检测。结果 该病例的引流液样本经显微镜检出形似葵花籽样虫体,低倍镜下观察具备华支睾吸虫成虫的典型结构,引流液样本经qPCR检测,为华支睾吸虫阳性。检测淡水鱼样本共100条,28条华支睾吸虫阳性,感染率为28%。结论 锦州义县地区存在野生淡水鱼感染华支睾吸虫情况,应加强防治工作,预防华支睾吸虫病的流行。

花青素/大豆分离蛋白智能包装膜特性及鱼肉新鲜度监测

以大豆分离蛋白(soybean protein isolate,SPI)为基材,紫薯花青素为指示剂,采用流延法制备可监测鱼肉新鲜度的智能包装膜,比较分析不同添加量紫薯花青素对膜性能的影响。结果表明,添加花青素后,膜的机械性能、阻隔性能和热稳定性均有所提高,添加量10%时,综合性能最好。傅里叶红外光谱、X射线衍射光谱和扫描电镜结果表明,花青素与大豆分离蛋白有着良好的相容性,两者之间形成了较强的分子间作用力。此外,花青素的加入显著增强了膜的抗氧化能力(P<0.05),添加量15%时,DPPH自由基清除率达到最大值85.84%。将膜应用于鱼肉新鲜度的检测,发现随着储藏时间的延长,鱼肉腐败变质,膜的颜色随之改变,能灵敏地反映鱼肉新鲜度的变化。

电子商务网站展示信息对生鲜鱼产品价格的影响研究

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白鱼粉储存环境对其品质变化的影响

试验旨在研究白鱼粉储存过程中品质的变化规律。将白鱼粉分别储存在模拟低温冷库(温度12、10、8℃,相对湿度55%RH)环境和自然常规环境(温度18~27℃,相对湿度50%~70%RH),通过分析白鱼粉的水分、新鲜度(挥发性盐基氮、生物胺、酸价、丙二醛)和卫生指标(霉菌总数、沙门氏菌)研究白鱼粉品质的变化情况。结果表明,低温环境和自然环境储存的白鱼粉品质相当。在自然环境储存253 d,白鱼粉的水分含量和水分活度有所增加,但水分含量不高于10%,水分活度低于0.7;挥发性盐基氮(VBN)、酸价、丙二醛和生物胺变化较小,白鱼粉新鲜度未发生明显变化;霉菌总数符合《饲料卫生标准》(GB 13078-2017)的要求,未检出沙门氏菌。研究表明,白鱼粉储存时,可以通过控制环境温度(<27℃)、相对湿度(<70℃)、储存时间(<6个月)以及加强空气流通的方法确保白鱼粉的品质。