Characterization of Glycerophospholipid Molecular Species in Two Species of Arcidaes (Scapharca subcrenata and Scapharca broughtonii)

In this study, the molecular species of glycerophosphocholine (GPCho), glycerophosphoethanolamine (GPEtn), glycerophosphoserine (GPSer), glycerophosphatidylinositol (GPIns), lysoglycerophosphocholine (LGPCho), and lysoglycerophosphoethanolamine (LGPEtn) from arcidaes Scapharca subcrenata and Scapharca broughtonii were characterized using direct infusion-tandem mass (shotgun) method for the first time. At least 201 and 303 glycerophospholipid (GP) molecular species were characterized, respectively. Most of the predominant GP molecular species contained polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Meanwhile, the arcidae lipids contained a high proportion of polar lipids (81.57–86.72% of total lipids). Among PL, phosphatidylcholine (30.53–32.04 mol%) and phosphatidylethanolamine (21.48–26.71 mol%) were dominant.     

Recovery of Chitin from Antarctic Krill (Euphausia superba) Shell Waste by Microbial Deproteinization and Demineralization

A two-stage fermentation process of deproteinization and demineralization was used to purify chitin from Antarctic krill shell waste. Two bacterial cultures were isolated and tested for the degradation of krill shell waste. According to the morphological examination, physiological tests, and applied molecular techniques conducted, isolates were identified as Bacillus subtilis and Lactobacillus plantarum. At a temperature of 37°C, both strains were cultivated separately in flasks containing krill shell waste. At determined periods of time, deproteinization and demineralization of residuals were measured. For deproteinization tests, the liquid phase fermentation of krill shell waste showed protein removal of 88.9% after 60 h. For demineralization tests, the liquid phase fermentation of krill shell waste showed calcium carbonate removal of 84.6% after 72 h. Fourier transform infrared spectroscopy (FTIR) analysis of chitin prepared by the process was carried out and compared with spectra of samples treated by strong acids and bases.     

The Forms of Fluoride in Antarctic Krill (Euphausia superba) Oil Extracted with Hexane and its Removal with Different Absorbents

Krill oils (KOs) were prepared using different extraction methods (hexane and supercritical carbon dioxide), different materials (heat-dried krill powder, freeze-dried krill powder, and freeze-dried krill tail meat powder), and different standing times during hexane extraction. The fluoride concentrations in the KOs were positively correlated with the protein concentrations. Absorbents were employed to remove fluoride from KO. Activated clay achieved the highest fluoride removal rate (70.66%), followed by calcium oxide (14.49%), activated carbon (11.97%), calcium chloride (9.32%), activated alumina (0.94%), and chitosan (0.52%). Meanwhile, the protein removal rates of the above absorbents were positively correlated with the fluoride removal rates.     

Protein Hydrolysates and Ultrafiltration Fractions Obtained from Krill (Euphausia superba): Nutritional,Functional, Antioxidant,and ACE-Inhibitory Characterization

ABSTRACT

Krill (Euphausia superba) was hydrolyzed by proteolytic enzymes in order to produce multifunctional bioactive peptides, and their functional properties were evaluated. Krill protein hydrolysate (KPH) by pepsin with 4-h hydrolysis showed the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and angiotensin I converting enzyme (ACE) inhibitory activities. The solubility and foaming properties of KPH were higher than those of the unhydrolyzed krill protein at a wide range of pHs. KPH was further fractionated based on molecular weight. The 1- to 3-kDa peptide fraction exhibited the highest DPPH scavenging activity (IC₅₀ value of 0.5 mg/mL), oxygen radical absorbance capacity (497.39 ± 4.31 µM TE/mg fraction), 2,2-azino-bis(3-ethylbenzthiazoline)-6-sulfonic acid cation radical scavenging activity (48.41 ± 0.23 µM TE/mg fraction), and reducing power (110.40 ± 2.07 µM TE/mg fraction). However, the < 1-kDa peptide fraction exhibited a higher ACE inhibitory activity than that of other fractions. The 1- to 3- and < 1-kDa peptide fractions are rich in aromatic and hydrophobic amino acids, respectively.     

南极磷虾(Euphausia superba)脂肪与蛋白含量的季节变化

为了有效提取营养功效和附加值均更高的磷虾油,对南极磷虾(Euphausia superba)资源的综合开发利用提供参考,利用2013年7-8月和2013年12月-2014年5月在南乔治亚群岛和南设得兰群岛附近海域采集的南极磷虾样品,采用索氏抽提法,分别用无水乙醇、丙酮、石油醚、正己烷、乙酸乙酯、环己烷6种常见的有机溶剂作为提取试剂,对南极磷虾体内的脂肪进行提取,并确定最佳萃取溶剂.同时对南极磷虾脂肪、蛋白含量的季节变化及其与体长的关系进行了分析.结果显示,无水乙醇为南极磷虾脂肪提取的最佳溶剂.南乔治亚群岛海域7-8月南极磷虾脂肪含量和蛋白含量(干重)分别为(22.03±0.51)％和(64.52±0.16)％;其中,全长小于40 mm的磷虾个体,脂肪与蛋白含量均显著高于全长大于40 mm的个体(P＜0.05).从南极的初夏到秋末,南设得兰群岛海域的南极磷虾脂肪含量呈逐渐上升趋势,由12月的(19.83±0.04)％上升至翌年4月的最大值(30.584±0.02)％;5月则略有降低,为(28.66±0.03)％.与此相反,南极磷虾的蛋白含量则是12月最高、4月最低,分别为(66.75±0.14)％和(58.02±0.23)％;脂肪含量与蛋白含量呈显著负相关(P=0.005).研究结果对南极磷虾渔业及其生产安排具有直接的指导意义.     

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.     

南极磷虾(Euphausia superba)起捕后蛋白自溶进程及其影响因素

为了有效保持南极磷虾(Euphausia superba)原料品质,实现其高质化利用,本研究选取冷冻南极磷虾作为研究对象,在实验室条件下以非蛋白氮(NPN)含量、三氯乙酸(TCA)可溶性蛋白含量与氨基酸态氮含量为指标,证实了南极磷虾NPN含量的变化可以表征蛋白自溶进程,且可以实现海上处理样品、运至陆地实验室后进行分析的目的。在此基础上,选取完整的及挤压破损的新鲜南极磷虾作为研究对象,以0~8 h南极磷虾样品的NPN为指标,研究了南极磷虾起捕后蛋白自溶进程以及挤压破损对该过程的影响。结果显示,南极磷虾起捕死亡后的1 h内,NPN无显著变化(P>0.05),1 h后NPN迅速增加,挤压破损加速了南极磷虾的自溶进程,因此,目前的拖网作业方式有待改进。     

南极磷虾及其制品中总砷含量的分析方法研究

本研究比较了电感耦合等离子体质谱法(ICP-MS)、氢化物发生原子荧光光谱法(HG-AFS)以及银盐法测定南极磷虾(Euphausia superba)及其不同形式制品总砷含量的适用性,并采用确定的检测方法对南极磷虾冻虾、南极磷虾粉和市售不同品牌南极磷虾油中的总砷含量进行了系统测定。结果显示,采用ICP-MS法、HG-AFS法及银盐法检测南极磷虾及其制品中的总砷含量,3种方法的加标回收率分别达到100.26%~110.48%、82.68%~98.50%和89.64%~94.89%,RSD均小于5%。 3种国标方法对于南极磷虾及其相关制品的测定结果基本一致,但与银盐法相比,ICP-MS法、HG-AFS法操作复杂,仪器昂贵。因此,银盐法可作为快速测定南极磷虾及其制品中总砷含量的首选方法。采用银盐法测得南极磷虾冻虾、虾粉和虾油中总砷含量分别为0.44~0.45 mg/kg、1.04~1.91 mg/kg、0.52~5.50 mg/kg。加快建立南极磷虾及其制品中无机砷定量及砷形态分析技术对于科学认识南极磷虾砷的安全性至关重要。     

Preparation,Gel Electrophoresis Analysis,and Nutritional Evaluation of a Functional Krill Protein Concentrate with Low Fluoride Level from Antarctic krill (Euphausia superba)

A functional krill protein concentrate (FKPC) with low level of fluoride was prepared from frozen Antarctic krill (Euphausia superba) using isoelectric precipitation and phosphoric acid treatment. Variations in proteins and nutritional properties of the FKPC were analyzed. Gel electrophoresis analysis indicated that some variations in protein composition were introduced by autolysis and pH shift during the process of isoelectric precipitation and fluoride removal. The FKPC was composed of 81.01% ± 0.45% crude protein (dry basis) and 16.78% ± 0.26% total lipid (dry basis), exhibited excellent amino-acid composition in all the essential amino acids, exceeding the requirements of the FAO/WHO/UNU for food protein, and was rich in omega-3 polyunsaturated fatty acids, especially eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids present in phospholipids. The fluoride level of FKPC was 79.79 ± 2.10 μg/g (dry basis), which met the USFDA requirements. The surimi yield reached 43.74%, and the mean recovery rate of protein and fat was 52.68% and 41.44%, respectively. The nutritional value, safe level of fluoride, and high yield rate provide evidence that FKPC has a promising future in the food industry as a new aquatic protein and lipid resource.     

Determination of Fatty Acid Composition and Phospholipid Molecular Species of Large Yellow Croaker (Pseudosciaena crocea) Roe from China

The aim of this study is to investigate the composition of the fatty acids and phospholipids derived from large yellow croaker (Pseudosciaena crocea) roe. The composition of the total lipids and the molecular species of phospholipids were determined by gas chromatography–mass spectroscopy (GC–MS) and high performance liquid chromatography–evaporative light scattering detector (HPLC–ELSD), respectively. The results showed that large yellow croaker roe had high levels of the total lipid (19.6% ± 1.32%, w/w) and phospholipid (61.2% ± 1.22% of the total lipid). The phospholipid was rich in docosahexaenoic acid (31.0% ± 0.19% of the total phospholipids), and the major phospholipid molecular species was phosphatidylcholine (PC, 61.06% ± 0.02% of the total phospholipids, w/w). It was concluded that large yellow croaker roe is expected to be a good resource of phospholipids with a high content of PC.     

牙鲆不同组织抗菌肽的提取及部分性质检测

以新鲜的牙鲆为试验材料,用100%丙酮和90%甲醇配制的提取液,从牙鲆的鳃、皮肤、肝、肾组织中提取抗菌肽,并对牙鲆抗菌肽粗提物进行部分性质检测。抑菌试验证明,牙鲆各组织提取物对大肠杆菌、鳗弧菌有较强的抑制作用,并且不同组织的抑制作用有所差别,而对金黄色葡萄球菌的抑制效果不明显。提取物经过加热处理后,抑菌圈略有变小。相反,经过胰蛋白酶处理后,抑菌圈略有变大。牙鲆的多种组织中含有对细菌有抑制作用的抗菌肽。     

Variation in Chemical Composition of Oils from Nile Perch (Lates niloticus) Belly Flaps with Capture Site and Season

Fatty material from Nile perch belly flaps, a major processing by‐product, was assessed for variation in fat content, fatty acid composition, vitamin A content, and level of contaminants in relation to capture site and season. Nile perch from Lake Victoria had higher material yield and omega-3 fatty acids (FAs) but lower content of vitamin A than those from Lake Albert. Levels of omega-3 FAs (4.36–20.20%) and vitamin A (2.83–7.88 mg/100 g of oil) were generally high. Levels of lead and cadmium showed significant variation with site. Material weight and vitamin A contents were higher, whereas FAs were lower in fish captured during the dry season than those in the wet season.     

Extraction Optimization and Characterization of Gelatin from Half-Smooth Tongue Sole (Cynoglossus semilaevis Gunther) Skin

Half-smooth tongue sole is a popular warm-water fish, and its skin may be an available resource for gelatin extraction. Response surface method was used to optimize the extraction of gelatin from the fish skin. The most suitable conditions for maximum gelatin yield (24.2%) were pretreatment with 1.9 g/L NaOH, followed by hot water extraction at 63.54ºC for 4.81 h. The obtained gelatin had a high imino acid content (185 residues/1,000 residues), with a high content of crude protein and low levels of ash, fat, and moisture. The predominant sodium dodecyl sulfate–polyacrylamide gel electrophoresis bands revealed that the gelatin contained low-molecular-weight peptides, α-, β-, and γ chains. As compared with bovine gelatin, the fish skin gelatin solution had lower values of strength and clarity and higher levels of L* and viscosity. Additionally, Fourier-transform infrared spectra showed that gel from the gelatin had four amide bands (amide A, amide I, amide II, and amide III) similar to commercial gelatin. The results suggest that half-smooth tongue sole skin could be a promising source of gelatin in view of the comparability between its gelatin and commercial gelatin in physicochemical properties.     

Extraction and Physicochemical Characterization of Pepsin Soluble Collagens from Golden Pompano (Trachinotus blochii) Skin and Bone

Pepsin-soluble collagen (PSC) was extracted and purified from wasted skin and bone of the golden pompano by acetic acid-pepsin method. The result showed that the PSCs extraction yields of skin and bone were 21.81% and 1.25% (wet weight), 62.21% and 1.78% (on the basis of lyophilized dry weight), respectively. Golden pompano skin and bone PSCs contained the typical chain of α and β dimers, and they were preliminarily judged to belong to type I collagen. The skin PSC had similar amino acid composition to bone PSC, which is rich in glycine, alanine, proline, and hydroxyproline. After addressing the pepsin, three helical structure of PSCs were intact, and their natural structures largely remained. The denaturation temperatures of skin and bone PSCs were 37.04°C and 38.23°C, respectively. Solubility results showed that the skin and bone PSCs solubility was the largest at pH = 3. The solubility of skin and bone PSCs was stable at NaCl concentrations lower than 3%. In addition, two PSCs in acid and low salt conditions had good solubility. This study demonstrated that golden pompano skin and bone could be used as good materials to extract PSC, representing an economic benefit and added value.

Abbreviations: SDS-PAGE: Sodium dodecyl sulfate polyacrylamide gel electrophoresis; FTIR: Fourier transform infrared; DSC: Differential scanning calorimetry; XRD: X-ray diffraction     

Antioxidant and immune defences of rainbow trout (Oncorhynchus mykiss) offered plant oils differing in fatty acid profiles from early stages

The antioxidant defence and immune response of rainbow trout (Oncorhynchus mykiss) that had received plant oils, rich in either n‐3 polyunsaturated fatty acids (PUFA; linseed oil) or n‐6 PUFA (safflower oil) was evaluated upon antigen exposure. The fish employed in this study had been offered the diets for 18 months from the first feeding. Rainbow trout from each group were injected intraperitoneally with formalin‐killed bacteria (Aeromonas hydrophila) or were sham‐injected and observations were made 24 h later. Though the fish fed safflower oil seemed to be under relatively greater oxidative stress, the antioxidant defences (superoxide dismutase, catalase, glutathione peroxidase) were as effective as in those fed linseed oil. The humoral (alternate complement activity and lysozyme activity) and cellular (phagocytic activity and lymphocyte proliferation) immune responses were not significantly affected by the oil offered. With the exception of reactive oxygen production that was significantly greater in the linseed oil fed fish, both groups did not differ greatly in their immune responses after antigen exposure. Thus, fish fed safflower oil that was deficient in n‐3 PUFA was able to sustain most of the critical responses similar to those fed linseed oil suggesting that plant oils of both fatty acid categories were effective for this fresh water fish.     

Changing population structure of eels (Anguilla dieffenbachii and A. australis) from southern New Zealand

Abstract –  Commercial catches of longfin and shortfin eels ( Anguilla dieffenbachii and A. australis ) were sampled from southern New Zealand in the mid-1990s to determine the status of the eel population. We compared this with historical information on eel populations to highlight changes in the status, and then investigated the likely causes of these changes. A total of 20,722 longfins and 2366 shortfins were sampled from 216 landings. Longfins dominated catches comprising 53–100% (mean = 90%) of eel numbers. Shortfins were predominantly, but not exclusively, coastal in their distribution, whereas longfins were widely distributed through all reaches sampled. Mean size of shortfin was invariably larger than longfin and for both species generally increased with distance inland, particularly for longfin in the longest rivers. There was no clear geographical separation of longfin sexes although females were more common further inland in the longer rivers. Longfin sex ratio was about 4:1 (male:female), whereas in shortfin it was nearly 100% female. There have been marked changes in the status of the eel population in southern New Zealand over the last 60 years. We suggest that commercial fishing has resulted in a reduction in the size of both species, and for longfins a skewing of the sex ratio toward males – fishing may have favoured differentiation into males as well as the removal of the longer-lived longfin females. Skewed sex ratio and small size of longfins compared with those of shortfin suggest that this species has been more affected by fishing pressure than shortfins, possibly allowing shortfins to expand their range further inland.     

Replacement of fish oil with vegetable oil blends in feeds for greater amberjack (Seriola dumerili) juveniles: Effect on growth performance,feed efficiency,tissue fatty acid composition and flesh nutritional value

This study was undertaken to assess the effects of fish oil (FO) substitution by a mixture of alternative vegetable oils (VO) on Seriola dumerili culture performance. A 154‐day feeding experiment was conducted using juveniles (39.2 ± 1.6 g average weight). Three isolipidic and isoenergetic meal‐based diets were formulated varying their lipid component. The control diet contained 100% FO (FO100), whereas diets VO50 and VO100 included 1/2 of oil blend and all the oil from blend of palm oil (PO) and linseed oil (LO) as substitute for FO, respectively. Dietary regime did not significantly affect growth performance, biometric indices, feed efficiency, plasma chemistry and liver and muscle lipid contents. Nonetheless, dietary VO inclusion impacted on the fatty acid profile of target tissues, especially in the liver. Fatty acid profiles of the fillets reflected those of the dietary oils except that there was apparent selective utilization of palmitic acid (C16:0) and oleic acid (C18:1n‐9) and apparent selective retention of long‐chain polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA, C20:5n‐3) and docosahexaenoic acid (DHA, C22:6n‐3). The nutritional value and the potential ability to prevent the development of coronary heart diseases of the flesh lipid fraction decreased with gradual FO substitution.     

Simultaneous Extraction and Fractionation of Fish Oil from Tuna By-Product Using Supercritical Carbon Dioxide (SC-CO2)

ABSTRACT

Fish oil was extracted and simultaneously collected into six fractions based on molecular weight and the chain length of triglycerides in terms of fatty acid constituents without splitting of the triglycerides, using supercritical carbon dioxide (SC-CO₂) at optimized conditions of 40 MPa, 65°C, and a flow rate 3 mL min^?1. In each type of fractionation, the first fraction (F1) was rich in saturated fatty acids (SFA; 52.57 to 61.26%), followed by monounsaturated fatty acids (MUFA; 22.17 to 23.22%) and polyunsaturated fatty acids (PUFA; (0.54 to 20.37%); the sixth fraction (F6) was rich in PUFA (48.93%), followed by MUFA (33.59%) and SFA (13.61%). It was obvious that short-chain fatty acids were extracted at an earlier fraction; therefore, the latter fractions were dominant in long-chain fatty acids, especially MUFA and PUFA. Thus, omega-3 fish oil (last three fractions) was successfully separated to be used as a value-added health product.     

The Variations in Proximate Chemical Composition and Fatty Acid Profile in Different Parts of the Thornback Ray (Raja clavata) Caught from Black Sea,Turkey

Proximate chemical composition and fatty acid (FA) profile of different parts and sexes of ray (Raja clavata) were compared. The proximate values of liver samples significantly differed from other body parts (p < 0.05). Pectoral fin had the highest moisture, protein, and ash contents (78.6, 20.5, and 1.2%, respectively). The highest fat content (39.7%) was observed for liver samples. A significant variation was also observed between sexes in terms of proximate and FA values (p < 0.05). The levels of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) varied between 27.1–32.1, 14.9–19.0, and 34.3–39.5%, respectively, in total fatty acid methyl esters (FAME). The highest total PUFA and docosahexaenoic acid (DHA) values were observed in the edible portion of liver for both sexes due to high contents of fat, despite the low values of % total FAME in comparison with other body parts. Significant variations among FA levels were observed for different body parts (p < 0.05). The highest DHA and eicosapentaenoic acid (EPA) values were found in the edible portion of the liver and calculated as 6.8 and 2.3 g/100 g, respectively, indicating the importance of utilizing the liver of this species.