鱼肉山药饼的生产技术

我国淡水鱼资源非常丰富,但由于淡水鱼本身的骨刺细小不易去除且带有土腥味,加工难度要大于海产鱼,其加工比例目前仅6%左右,大量的淡水鱼以鲜货销售为主,严重制约了淡水渔业的发展。淡水鱼加工产品以冷冻产品、     

怎样去除淡水鱼的土腥味

养殖的淡水鱼类之所以价格不高,除了肉质较松及鱼刺多外,主要是容易含有土腥味。经研究发现,土腥味是水中的藻类及微生物所引起的,鱼腥藻、放线菌属等含有的土腥素是淡水鱼带有土腥味的罪魁祸首,特别是水温高、有机质高的水体越易产生。那么怎样去除呢？解决的方法有以下几种:一是清除塘底过多淤泥;二是经常换水;三是减少饵料残留;四是用化学药剂控制池中藻类;五是将上市鱼在干净水中蓄养几天。如根据规定,出口活鳗停饵时间不得低于４８小时,在清水中蓄养须在１２小时以上,以消除异味,提高品质怎样去除淡水鱼的土腥味     

用添加剂去除鱼的土腥昧

北京市农业局水产技术推广站研究成功去除养殖淡水鱼土腥味的技术。通常养殖的淡水鱼有土腥味等异味，食用口感差，养殖效益低，还存在食物中毒隐患。该站研究人员研究确定，有4种藻类是引起鱼肉带土腥味的物质，其中蕾纤维藻能引起土腥味在国内外尚属首次报道。他们同时还研究出有效去除土腥味的多种方法，其中在养殖池中施用生物制剂和在饲料中添加L-肉毒碱两种方法为国内外首创。该成果能使人们吃上不但安全而且优质的水产品。     

鱼的土腥味从哪儿来?

<正>同样是鱼,为啥有的土腥味那么重,是不是加了药?很多人有这样的疑问。鱼的土腥味到底是从哪里来?又该怎么去除呢?上海海洋大学食品学院水产品加工及贮藏工程系主任、教授陈舜胜告诉记者,淡水鱼如鲤鱼、草鱼、鲢鱼等一般都有土腥味,这与其生长环境有密切关系。含有土腥味的细菌附着在硅藻、蓝藻等浮游生物以及一些水草上,淡水鱼通过食物链会摄入这些物质,随之进入肌肉、血液和组织细胞。大江、大河、水库等大水面的水体     

不同清水暂养和排酸时间对银鲑肉质的影响

为解决封闭式循环水养殖银鲑(Oncorhynchus kisutch)的土腥味及不同的存储排酸时间对肉质的影响，将体质量2.50 kg的银鲑充气暂养在容水400 L的体积500 L的帆布桶中，采用盐度30海水和淡水，计算暂养过程中银鲑体质量的损耗率和屠宰率，通过感观评价和检测二甲基异茨醇(2-methylisoborneol, MIB)的含量，确定最佳暂养用水；同时，暂养后的鱼肉置于保鲜盒中，0℃冰箱存储0 h、24 h、48 h、72 h，通过感官评价确定最佳排酸时间。结果表明：两种清水暂养均有利于土腥味的消除，但海水暂养效果明显好于淡水，海水暂养的第7 d，感官评分为(9.49±0.11)，无土腥味，MIB含量为(0.22±0.038)μg/kg，明显低于0.7μg/kg，且银鲑屠宰率为(89.60±0.01)%，符合养殖要求，因此，最佳暂养条件为：海水，7 d。暂养鱼肉在0℃存储24 h后，感官评分达到最大值(14.90±0.12)，因此最佳排酸时间为24 h。本结果可为银鲑最佳暂养用水的选择和销售前期鱼肉品质的保障提供技术参考。     

去除鱼类土腥味养殖系统的构建技术研究

以团头鲂、鲫鱼为试验对象,构建了一种基于人工生态系统的循环水养殖系统。通过底层陶粒吸附细菌、流水养鱼加快鱼类的代谢、湿地去除氨氮提高鱼的活性、生化箱培养硝化菌和反硝化菌来调控水质并起到控制水流速度的作用等技术手段来去除鱼类土腥味,同时研究不同盐度对其调控效果的影响。结果表明:本养殖系统对水体中的藻类和放线菌以及鱼体中的放线菌有明显的抑制作用。把(土池)池塘内养殖的鱼放入系统中暂养,一个月后土腥味显著降低,3个月后土腥味几乎消失;且随着水体盐度的升高,效果越加明显。     

低值淡水鱼加工利用研究进展

世界水产养殖总产量中淡水鱼占 42 % ,产值占 34%。目前 ,发达国家的水产品加工率在 80 %以上 ,而我国的水产品加工率不足 30 % ,其中淡水鱼加工率不到 1 0 % ,部分原因是淡水鱼固有的土腥味给加工带来了难度。由于淡水鱼产品上市期比较集中 ,肉质细嫩 ,营养丰富 ,水分含量高 ,鱼体内组织酶活跃 ,易腐败。受贮藏加工条件的限制而造成的淡水鱼类腐败率在 30 %以上 ,我国淡水鱼加工技术的落后已经严重制约了淡水渔业的发展。本文就低值淡水鱼的加工现状进行了研究分析 ,提出了可能采用的途径 ,旨在为我国从事淡水鱼加工生产及综合利用研究方面…     

淡水鱼肉粒的加工研制技术（下）

(3)脱腥技术的探讨在淡水鱼中有一种特殊的土腥味,这种土腥味随着鱼品鲜度的下降或加工成制品后存放时间延长更为浓重,淡水鱼的土腥味大多存在于鱼体表粘液中,当粘液和空气接触后会产生一种令人不愉快的特殊味道。据研究,其腥味的主体成份是呱啶类衍生物、戊酸等物质。在本研究     

淡水鱼美味巧处理

淡水鱼味道鲜美且营养丰富,但烹调出来常常会有很重的土腥味,口感不如海水鱼.笔者从有关水产专家处了解到,淡水鱼的生长环境往往是腐殖质较多的池塘、河川、湖泊,其中繁殖有较多的放线菌,它们会通过鱼鳃浸入鱼体血液,分泌一种具有恶臭(即土腥味)的褐色物质,从而导致淡水鱼腥味重.     

淡水鱼冬季暂养效益高

由于淡水养殖是春放冬捕,往往导致冬季淡水鱼市场饱和,而春夏季淡水鱼上市较少,造成市场供应淡旺不均。实践证明,进行淡水鱼暂养,既可调节市场,又能提高经济效益,一举多得。淡水鱼暂养技术如下: 1、暂养鱼选择:暂养鱼最好是冬季滞销,春夏季畅销、且耐低温贮养的品种,如银鲫、鲢、鳙、鳊鱼是比较合适的品种,这些鱼不仅耐低温贮养,而且在暂养期间还能增重。暂养鱼的规格最好是接近上市的规格,一般为:银鲫每尾100-150克,鲢、鳙鱼每尾400克左右,鳊鱼每尾150-250克;经过暂养增重,这些鱼都能达到市场畅销的规格。 2、暂养鱼下池:可利用冬闲鱼种池作暂养池。暂养池清整后,施一定量的基肥,一般每667平方米     

Physiology Approaches to the Management of Off-Flavors in Farm-Raised Channel Catfish,Ictalurus punctatus

To obtain optimal yields of channel catfish, Ictalurus punctatus, large quantities of feed are added to ponds. Nutrients released from feed support dense algal and bacterial populations. Although some microbes produce oxygen and remove wastes, certain taxa produce the muddy/earthy off-flavor metabolites, 2-methylisoborneol (1-R-exo-1, 2, 7, 7-tetramethyl-bicyclo-[2, 2, 1]-heptan-2-ol) (MIB) and geosmin (1α, 10β-dimethyl-9α-decalol). Currently, off-flavors are one of the biggest problems affecting the channel catfish industry. Fish exposed to water containing either geosmin or MIB rapidly concentrations of these compounds in their tissues. Conversely, fish placed in water free of off-flavor metabolites exhibited markedly reduced concentrations of MIB after 8 hours and continued to improve in flavor quality throughout 24 hours, indicating a progressive purging or clearing of off-flavor compounds from their tissues. Relatively lean (< 2.5% fat) fish lost MIB more rapidly than fish with greater fat contents (> 2.5% fat). This paper proposes that aquaculture production systems should be managed for maximum production efficiency and yields, and that fish containing off-flavors then could be purged in special facilities. Purging systems that rely on a constant flow require large amounts of water and may not be widely practical. Systems that recirculate water may be more feasible. However, biological filters and other components of recirculating systems may become sources of off-flavors. The early detection of off-flavor-producing taxa and the competitive exclusion of problematic populations may be useful in preventing off-flavor production in recirculating purging systems.     

Culture environment and the odorous volatile compounds present in pond-raised channel catfish (<Emphasis Type="Italic">Ictalurus punctatus</Emphasis>)

A headspace solid-phase micro-extraction (SPME) coupled with GS-MS method was used to measure volatile compounds in fillets from musty off-flavor, muddy off-flavor, and on-flavor channel catfish (Ictalurus punctatus), along with water and soil samples from the farm ponds in which the fish had been raised. Two ponds of each type of flavor were selected, and five fish, water, and soil samples were collected from each pond. Linear and multiple linear regression analyses were carried out between/among off-flavor strength and volatile compound contents to investigate their possible correlations. The combination of two strong off-flavor compounds, 2-methylisoborneol (MIB) and geosmin (GSM), was probably mainly responsible for the musty off-flavor in the catfish fillets, and an odorous alcohol, 1-hexanol, was correlated with muddy off-flavor (p =?0.015). There was a strong correlation between beta-cyclocitral and MIB in a pond that gave musty off-flavor catfish contents (p =?0.006), suggesting that these compounds might be generated by similar cyanobacteria. The contents of GSM, MIB, and beta-cyclocitral were high in the water of ponds that yielded off-flavor fish, indicating that catfish might acquire these compounds from pond water.     

Variation in Channel Catfish Ictalurus punctatus Flavor Quality and its Quality Control Implications

Abstract Producers may capture two to three channel catfish Ictalurus punctatus L. for flavor analysis from ponds scheduled for harvest. If off-flavors are not present in several consecutive fish samples, the population may be considered acceptable for harvest. However, instrumental analysis of the muddy/earthy off-flavor metabolites 2-methylisoborneol (1-R-exo-1,2,7,7-tetramethyl-bicyclo-[2,2,1]-heptan-2-ol) (MIB) and geosmin (lα, 10β-dimethyl-9α-decalol) concentrations in approximately 80 catfish from each of three commercial ponds found both acceptable (on-flavor) and unacceptable (off-flavor) individuals within a single pond (i.e., mixed-flavor populations). Ascertaining the frequency of mixed-flavor populations by instrumentally determining the off-flavor metabolite concentration in muscle tissues from a large number of fish sampled from many ponds at several locations over time is not currently feasible. However, analysis of 12,725 commercial processor flavor assessments collected in 1994 and 1995 indicated 120 instances of individual ponds yielding off-flavor fish followed by on-flavor fish in one day or less. Reports indicate that fish require approximately four days to depurate off-flavors fully, suggesting that a proportion of these rapidly changing flavor assessments may reflect the stochastic selection of fish from mixed-flavor populations rather than a complete and rapid conversion of the flavor quality of entire populations. Factors that contribute to the occurrence of mixed-flavor-populations have not been identified fully. However, increased proportion of fat in catfish fillet tissues has been reported to be correlated with a greater retention of MIB by fish. In this investigation, fish fat contents ranged from 4.45% to 30.45%, and were positively correlated (P < 0.0001) with MIB concentrations. Additionally, the spatial distributions of algal populations within certain commercial catfish ponds were not uniform, and the sensory analysis of the flavor intensity of MIB and geosmin in catfish was more variable than the assessment of the intensity of chickeny and nutty flavors. Probability analysis indicated that in certain mixed-flavor populations there was a 10 to 25% probability of a shipment of fish being rejected due to the random collection of only on-flavor fish prior to harvest followed by the post harvest capture of at least one off-flavor fish. In addition, a chance of no off-flavor fish being sampled from a population containing a proportion of unacceptable fish was indicated. At current sample sizes, replacing sensory analysis with instrumental analysis would not completely avoid problems associated with sampling mixed-flavor-populations. Until effective means to reduce/avoid off-flavor metabolite accumulations in fish are widely available, careful attention to proper sensory evaluation protocols, an enhanced attention to pond conditions that affect flavor quality, the production of leaner more uniform populations of fish, and optimizations of sampling strategies offer the most practical near-term augmentations of current practice.     

Effects of Temperature on the Uptake and Depuration of 2-Methylisoborneol (MIB) in Channel Catfish Ictalurus punctatus

The microbial metabolite 2-methylisoborneol (MIB) imparts a muddy off-flavor to channel catfish Ictalurus punctatus . Uptake and depuration of MIB from fish are important considerations in the design and implementation of systems to remove off-flavors from fish prior to processing. The kinetics of MIB uptake by channel catfish were determined by placing fish in 6.5, 14.0, 25.0, and 34.0 C water containing approximately 1.0 μg/L chemically-synthesized MIB. Fish were sacrificed following 0, 2, 4, 8, and 24 h exposure to MIB. Fillet tissue samples were subjected to gas chromatographic and fat content analysis. The model for MIB uptake was:
MIB in fillet tissue (μg/kg) =−0.61 ± 4.2 [log( h ± 1)] ± 0.0076( T ) ( h ) ± 0.089( T ),
where h is the duration of exposure to MIB in hours and T is the water temperature in degrees C. The model accounted for 74% of the total variation observed in the tissue MIB concentrations and indicated that the fillet fat content was not strongly correlated with MIB uptake. To investigate the depuration of off-flavors, exposure to MIB was halted. Tissue samples were obtained 4, 8, 24, 48, and 72 h from fish held at 6.5, 14.0, 25.0, and 34.0 C. These data yielded the model:
MIB in fillet tissue (μg/kg) = 3.6 ± 0.176( T ) – 2.06 [log( h ± 1)] – 0.00296( T ) ( h ) ± 0.197 (% fat),
where h is the duration of exposure to MIB in hours, T is the water temperature in degrees C, and % fat is the % fat in the fillet tissue. The model accounted for 67% of the total observed variation in tissue MIB concentrations. Reducing the fat content of fish and optimizing water temperatures may augment MIB removal from fish tissues prior to processing.     

脱二氧化碳装置对循环水养殖系统pH的影响

为了调节循环水系统中养殖水体的pH,根据气体交换原理,设计一种脱二氧化碳(CO_2)装置。采用该装置去除养殖水体中的CO_2,并对由于CO_2含量累积造成的pH下降进行调节,使养殖鱼类处在一个适宜的pH环境中。试验时水温控制在(25±0.5)℃,每1 h取水样测1次pH,每4 h测1次碱度。水样取自养鱼桶内的水,检测前先对水样用40μm孔径针头过滤器进行过滤处理,实验周期24 h。结果显示,循环水系统加装脱二氧化碳装置能有效去除CO_2,使水体稳定在一个适宜的pH范围(7.39~7.42);CO_2质量浓度呈降低趋势,24 h后由开始的13.16 mg/L降低到7~8 mg/L,降低近50%,而不加装脱二氧化碳装置的循环水系统CO_2质量浓度持续上升,24 h后增加到37 mg/L左右,pH持续降低,最终降低到6.72~6.81。研究表明,脱二氧化碳装置能够有效去除水体中的CO_2,使水体pH维持在一个适宜鱼类生长的范围。     

海蜇人工育苗关键技术

在200m^3水体培育出海蜇16触手螅状体600万个，关键技术在于育苗用水严格砂滤防止藻类和固着纤毛虫进入；育苗池中防止裸露的钢筋铁管严禁重金属离子污染；亲蜇成熟度好；采苗器严格消毒；4触手期保证适口饵料供应；防止高温季节螅状体与饵料一起死亡。另外，根据上年的经验，今年春这些螅状体要想生产出更多的幼蜇需掌握以下关键技术：培养大规格的螅状体；控光控温诱导横裂生殖集中释放碟状体；光线控制在500—1000lx；保持水质新鲜。     

Off-flavors in pond-grown ictalurid catfish: Causes and management options

Ictalurid catfish grown in ponds often acquire undesirable off-flavors prior to harvest. Off-flavors develop when odorous, lipophilic substances in food or water are absorbed across gut or gill epithelium and concentrated in edible tissues. The most common causes of catfish off-flavors are two nontoxic secondary metabolites of planktonic cyanobacteria: geosmin (causing an earthy off-flavor) and 2-methylisoborneol (causing a musty off-flavor). Off-flavored fish are unacceptable for processing, and harvest must be postponed until the source of the odorous compound disappears and the compound purges from edible fish tissue. Harvest delays caused by episodes of off-flavor increase production time, interrupt cash flow, and increase the risk of fish loss. Catfish farmers consider off-flavor to be one of their most important production-related problems. This paper reviews the causes of off-flavor in catfish, pharmacokinetics of uptake and loss of odorous compounds in catfish, seasonality and prevalence of off-flavors, farm- and industry-level impacts, the ecology of cyanobacteria in catfish ponds, and various strategies for preventing or treating cyanobacterial (and other) off-flavors. A decision-making system based on knowledge gained from research is presented as a guide to effective use of the limited tools available to manage off-flavors.     

Factors influencing the efficacy of MS-222 to striped mullet (Mugil cephalus)

Some responses of juvenile striped mullet (Mugil cephalus) to the anesthetic MS-222 were investigated. Induction times to total loss of equilibrium decreased with increasing anesthetic concentration over the range of 40–120 ppm. Temperature, pH, and oxygen concentrations all significantly affected induction times to total loss of equilibrium in freshwater-adapted fish at a concentration of 80 ppm MS-222. Anesthetic toxicity was less for saltwater-acclimated fish than for freshwater-acclimated fish. The 24-h 50% mortality (LC₅₀) in fresh water was 33.1 ppm; in salt water it was 39.8 ppm. The results suggest that anesthetic action may be intensified in fish acclimated to conditions other than those near their physiological optima.     

漠斑牙鲆仔鱼、稚鱼和幼鱼对低盐度的耐受力和淡水驯化技术的研究

研究了漠斑牙鲆仔鱼、稚鱼和幼鱼对低盐度的耐受力和漠斑牙鲆的淡水驯化技术。初孵仔鱼在盐度为5的水中最多存活5d,5d以后全部死亡。30日龄稚鱼在4h10min淡水组全部死亡,对淡水的耐受力较低,而盐度为5～25的各组72h的存活率都在95.00%以上。90日龄幼鱼经缓慢淡水驯化9d后存活率可达98%以上,对漠斑牙鲆幼鱼进行淡水驯化的最佳年龄为90日龄。淡水驯化影响幼鱼初期的摄食,以后则逐渐趋于正常;急性淡水驯化对幼鱼的伤害比缓慢淡水驯化大;漠斑牙鲆对低盐的耐受力随生长和发育逐渐增加,年龄是影响幼鱼对低盐度耐受力的主要因素。     

Controlling of geosmin and 2‐methylisoborneol induced off‐flavours in recirculating aquaculture system farmed fish—A review

Recirculating aquaculture system (RAS) is an increasingly popular alternative to open aquaculture production systems. However, off‐flavours and odours can accumulate in the fish flesh from the circulating water and decrease the fish meat quality. Off‐flavours are typically caused by geosmin (GSM) and 2‐methylisoborneol (MIB) that are lipophilic compounds formed as secondary by‐products of bacterial metabolism. Even though GSM and MIB are not toxic, they often are disliked by consumers, and both have very low human sensory detection limits. Multiple methods have been suggested to remove or decrease GSM and MIB in fish, including ozonation, advanced oxidation processes (AOP)s and adsorption removal from water using activated carbon and/or zeolites. So far, purging with fresh water is the only efficient method available to remove the off‐flavours. There are multiple analytical methods available for the extraction and separation of GSM and MIB from fish flesh and water. This review discusses the current knowledge of GSM and MIB formation, the challenges faced by RAS farms due to these compounds and process solutions available for their removal.