Nutrient Compositions and Properties of Antarctic Krill (Euphausia superba) Muscle and Processing By-Products

ABSTRACT

This study investigated the morphometrics, proximate chemical compositions, pH, total amino acid (TAA), fatty acid profile, and minerals of the processing by-products of Antarctic krill (Euphausia superba). The nutrient compositions and properties of the by-products were revealed by being compared to those of Antarctic krill muscle and the economically important species of freshwater prawns (Macrobrachium nipponense) and penaeid shrimps (Metapenaeus ensis). The by-products are worthy of utilization because of the high ratio to the total weight (65.7%). The crude protein contents in the muscle and by-products of krill are 17.4 and 11.7%, respectively. The krill proteins have higher contents of essential amino acids (EAAs). The EAAs constitute 42 and 37% of the TAAs in muscle and by-products, respectively. The krill processing by-products contain high levels of total lipid (3.3%), and polyunsaturated fatty acids constitute 34% of fatty acids with high levels of eicosapentaenoic acid (EPA; 19.08%) and docosahexaenoic acid (DHA; 10.02%). Krill meat provides considerable iron, zinc, calcium, selenium, and copper. It is imperative to lower the fluoride level (70.1 mg/kg, wet basis) in krill muscle. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) reveals that myosin heavy chain (MHC) and actin are the major proteins in muscle, and their contents vary between species.     

不同饲料对哲罗鲑生长性能和营养成分的影响

在人工养殖条件下,分别投喂野生鲫鱼和人工饲料对哲罗鲑生长性能和营养成分进行比较。每组养殖实验鱼50尾,每个实验组设3个重复,试验水温10.8～16.5℃,pH值7.2～7.5,溶氧〉6.0mg/L,试验共进行56d。试验结果：野生鲫组增重率、特定生长率、肥满度、水分均显著高于人工饲料组（P〈0.05）。野生鲫组粗脂肪显著低于配合饲料组（P〈0.05）。两试验组鱼体粗蛋白、粗灰分、肌肉氨基酸含量及组成差异均不显著（P〉0.05）。野生鲫组与人工饲料组相比,野生鲫组哲罗鲑生长性能较好,鱼体成分发生改变,而肌肉氨基酸营养价值未发生变化。     

Limnology of Macrobrachium amazonicum grow‐out ponds subject to high inflow of nutrient‐rich water and different stocking and harvest management

We evaluated the water characteristics and particle sedimentation in Macrobrachium amazonicum (Heller 1862) grow‐out ponds supplied with a high inflow of nutrient‐rich water. Prawns were subject to different stocking and harvesting strategies: upper‐graded juveniles, lower‐graded juveniles, non‐graded juveniles+selective harvesting and traditional farming (non‐grading juveniles and total harvest only). Dissolved oxygen, afternoon N‐ammonia and N‐nitrate and soluble orthophosphate were lower in the ponds in comparison with inflow water through the rearing cycle. Ponds stocked with the upper population fraction of graded prawns showed higher turbidity, total suspended solids and total Kjeldahl nitrogen than the remaining treatments. An increase in the chemical oxygen demand:biochemical oxygen demand ratio from inlet (4.9) to pond (7.1–8.0) waters indicated a non‐readily biodegradable fraction enhancement in ponds. The sedimentation mean rate ranged from 0.08 to 0.16 mm day^?1 and sediment contained >80% of organic matter. The major factors affecting pond ecosystem dynamic were the organic load (due to primary production and feed addition) and bioturbation caused by stocking larger animals. Data suggest that M. amazonicum grow‐out in ponds subjected to a high inflow of nutrient‐rich water produce changes in the water properties, huge accumulation of organic sediment at the pond bottom and non‐readily biodegradable material in the water column. However, the water quality remains suitable for aquaculture purposes. Therefore, nutrient‐rich waters, when available, may represent a source of unpaid nutrients, which may be incorporated into economically valued biomass if managed properly.     

Effects of marine fish farming on nutrient composition and plankton communities in the Eastern Aegean Sea (Turkey)

The hypothesis that the presence of fish farming zones affects the water quality and plankton communities was investigated in an Aegean Sea fish farm during February, June, September and January 2000–2001. In the spatial coverage, a total of 12 stations were sampled; three of them were reference stations. A variance analysis was applied to the measurements made at the stations near the fish farms and at the control stations. While no significant differences in concentrations of nutrients, chlorophyll a, particulate organic carbon and particulate organic nitrogen were detected between the stations and the control sites within one season, significant differences were detected between the parameter values measured except for total dissolved phosphorus and dissolved organic phosphorus at different seasons. The seasonal differences were also significant with regard to the biodiversity. Together with these temporal differences in general, there was a higher diversity of species at the control site as compared with the other stations in September, which was the key season to detection of significant changes. The most important consideration is that it is not sufficient to take the instantaneous values for the physico‐chemical variables; rather, it is necessary to monitor the biological parameters in order to define the differences in the ecosystem.     

青蟹的营养需求研究及其配合饲料研制

青蟹属（Scylla）有锯缘青蟹（Scylla serrata），拟穴青蟹（S．paramamosain），紫螯青蟹（S．tranquebarica）和榄绿青蟹（S．olivacea）等4个种。我国以拟穴青蟹占绝对优势，它有个体大、生长快、适应性强、肉味鲜美、营养丰富等特点，已成为具有重要经济价值的海水养殖蟹类之一。     

竹叶抗氧化物浸泡-乳清分离蛋白涂膜对冷藏富硒虹鳟蛋白质理化性质的影响

为从蛋白质水平解释竹叶抗氧化物浸泡-乳清分离蛋白涂膜对富硒虹鳟的保鲜机理,实验将鲜活富硒虹鳟去除头、内脏和表皮,切块后浸泡在1.0%的竹叶抗氧化物（AOB）溶液中（去离子水作为对照）,再进行乳清分离蛋白（WPI）溶液涂膜,25℃下鼓风吹干表面水分后置于4℃冰箱中贮藏1、4、7、10和13 d。测定鱼肉中肌原纤维蛋白和TCA-可溶性肽的含量、蛋白质的分子内价键,以及肌原纤维蛋白的总巯基含量、表面疏水性和二级结构,分析涂膜对冷藏富硒虹鳟蛋白质理化性质的影响。结果显示,冷藏期间,WPI组的肌原纤维蛋白含量和二级结构中β-折叠的含量显著高于对照组。冷藏1～7 d,WPI组的TCA-可溶性肽和二硫键含量以及表面疏水性指数（H₀）显著低于对照组,总巯基含量呈相反趋势,但随着冷藏时间的延长这些差异逐渐减弱。冷藏13 d时,WPI组与对照组无显著差异。3个实验组中,1.0%AOB+WPI组的肌原纤维蛋白、总巯基、氢键、二级结构中α-螺旋和β-折叠的含量在冷藏期间最高,H₀、TCA-可溶性肽、二硫键和二级结构中β-转角含量最低。WPI在鱼块表面形成一层薄膜,可...     

Investigations on the digestibility and metabolizability of the major nutrients and energy of maize leaves and barnyard grass in grass carp (Ctenopharyngodon idella)

In the uplands of northern Vietnam, culture of grass carp contributes significantly to income and household food security of Black Thai farmers. Maize is one of the most important upland crops and barnyard grass is the most important weed in the paddy rice fields. Thus, these are frequently used by small‐scale fish farmers as fish feed. An 8‐week feeding trial was conducted simultaneously in a recirculation and in a respirometric system to determine the digestibility and metabolizability of the nutrients of maize leaves and barnyard grass, to assess their crude protein, lipid and energy conversion and to estimate the energy allocation in grass carp. The following diets were used: diet ‘A’ (reference diet) containing 39% crude protein with 19.8 MJ kg^?1 gross energy; diets ‘B’, ‘C’ and ‘D’, which contained the same amount of the reference diet as the control diet, supplemented with a known amount of dried barnyard grass, dried maize leaves or fresh maize leaves, respectively. Five fish were assigned to each treatment in each experimental unit. Reference and test diets were fed to fish and faecal samples were collected and the oxygen consumption was measured in order to set up an energy budget of the fish over the whole experimental period. The weekly development of the body weight was recorded. The body weight gain of the fish fed diet D was significantly higher than that of the group fed diet A, which also in turn was significantly higher than that of fish fed diet B or C. The apparent digestibility coefficients (ADC) of nutrients and gross energy for the different experimental diets in fish kept in the aquaria were, for diets A, B, C and D respectively, 94.1%, 60.9%, 70.5% and 84.7% for protein, 91.3%, 60.7%, 76.8% and 71.8% for lipid; 95.9%, 44.5%, 60.6% and 69.1% for gross energy. The partial ADC of plant leaf ingredients were determined and barnyard grass and dried maize leaves were found to be not only poorly digestible but having negative impact on the digestibility of the reference diet, while fresh maize leaves were well digested. The results of the present study indicated that fresh maize leaves have a good potential to be used as supplement in diets for grass carp.     

赤[鱼工]肌肉的营养成分及鱼松保健食品的试制

对赤鱼工肌肉营养成分进行了分析 ,其粗蛋白含量为 2 0 6 % (干基为 6 4 7% ) ;氨基酸分析结果表明 ,第一限制氨基酸为色氨酸 ,氨基酸评分为 92分 ,蛋白质营养价 ;无机质含量丰富 ,微量元素Se含量为 0 91mg/kg (干基 4 2 3mg/kg) ,Cu为 1 38mg/kg (干基为 6 4 2mg/kg) ,是含Se、Cu很高的水产品。赤鱼工肌肉经加工处理 ,可制得味美可口且食用方便的赤鱼工肉松     

蓄水前后三峡水库营养盐收支计算

根据近10年来长江三峡库区江段氮、磷营养盐的历史数据,以及三峡库区支流、大气降水、地表径流、淹没土壤释放、工农业排放等主要形式的氮、磷营养盐负荷数据,并结合现场调杏的结果,采用箱式模型对蓄水(135～139m)前后三峡水库营养盐进行收支计算,以期为三峡成库后三峡江段生源要素生物地球化学过程以及长江营养盐输送过程提供研究基础.结果表明:上游输入的总氮、总磷是三峡水库氮、磷营养盐的主要来源,占入库负荷的80%～90%;蓄水后入库营养盐负荷种类增加,主要是淹没土壤的释放作用.蓄水前总氮、总磷入库负荷与出库负荷相等,蓄水后入库营养盐有约18%的总氮和15%的总磷滞留于水库中,而溶解无机氮、溶解无机磷受蓄水因素影响较小.颗粒氮磷营养盐的沉降、生物吸收以及残体的沉降作用是导致出库营养盐减少的主要原因,其过程有待进一步深入研究.     

鲇形目亲鱼和仔稚鱼营养需求特点研究进展

正鲇形目鱼包含35个科。其中斑点叉尾(Ietalurus punetaus)、黄颡鱼(Pelteobagrus fulvidraco)、长吻(Leiocassis longirostris)、斑鳠(Mystus guttatus)、胡子鲇(Clarias fuscus)等品种肉质鲜美、营养丰富,是我国重要的淡水经济鱼类,深受广大消费者的青睐。鲇形目鱼类的市场需求持续增加,养殖规模也不断扩大。有关鲇形目鱼幼鱼、成鱼等营养饲料方面的研究报道较多,但其亲鱼和仔稚鱼营养素需求及配合饲料研究相对滞后。