Evaluation of the potential use of discard species for fish silage and assessment of its oils for human consumption

Waste or by-products contains a substantial amount of nutrients. Fish silage is an alternative way for assessment of fish discards and waste generated in the fish processing industries. The aim of the study was to evaluate the potential use of discard species (Equulites klunzingeri, marine fish and Carassius gibelio, freshwater fish) for fish silage and chemical quality of fish oil extracted from fish silages prepared with acid and fermented methods. Lipid quality of fish oils extracted from fish silages with LAB strains was evaluated in terms of thiobarbituric acid (TBA), peroxide value (PV), p-Anisidine (AV), totox values and fatty acid composition. The results showed that PV, TBA, AV and totox values of all extracted fish oils were within the acceptable limits for edible oils. Recovered fish oils from silage contained high level of polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), serving as a source of good quality fish oil for human consumption.     

Flavour studies with fish meals and with fish oil fractions in broiler diets

Fish meals extracted with ethanol, benzene and/or warm water or acidified water were included in diets for broilers at 20 % levels, while in some instances certain amines, phospholipids from the fish oil extracted from fish meal (here called “residual” fish oil) and triglycerides from such fish oil were added to broiler diets singly or in different combinations. The experimental diets were given to broilertype chickens from their fifth week until they were slaughtered when 81/2 weeks old. Carcasses from the different treatment groups were subjected to organoleptic evaluation and the fatty acid make-up of the fat in the carcasses and of the oils in the fish meals, determined by gas chromatography. Carcasses of chickens which received diets containing fish meal extracted with the fat solvents consistently had a chicken flavour. When the diets contained fish meal extracted with warm water or a warm, weak, acid solution the carcasses had a neutral flavour. Unextracted fish meal and the triglyceride fraction of fish oil (at a 2.0 % level) in the diet invariably produced carcasses with a “fishy” taint. The phospholipid fraction of “residual” fish oil had no effect on carcass flavour while additional amines (trimethylamine, ethanolamine and choline) in the diet in most instances aggravated the foreign taint. The high correlation between flavour score and the levels of certain highly unsaturated fatty acids in the chicken carcasses was confirmed.     

微波辅助萃取罗非鱼鱼油工艺优化及脂肪酸分析

罗非鱼经冻干粉碎后,采用微波辅助法萃取罗非鱼鱼油,通过单因素和正交实验确定其最佳工艺条件。使用气相色谱仪分析萃取的鱼油(整鱼、鱼头、鱼尾、鱼皮、鱼肉和内脏)脂肪酸组成。根据国家标准检测整鱼及各个部位油脂理化指标。结果表明:正己烷为最佳萃取溶剂,当料液比1:10 (g/mL),萃取时间10 min,微波功率100 W时,整鱼鱼油萃取率最高为29.17%±0.13%;整鱼及各个部位的鱼油脂肪酸主要由棕榈酸(20.98%~23.20%)、油酸(19.06%~25.96%)和亚油酸(10.38%~15.74%)组成;整鱼及各个部位中,鱼肉DHA+EPA的含量最高(3.29%±0.07%),鱼尾次之(3.10%±0.03%)。所得鱼油理化指标均符合国家标准。因此,经微波辅助法提取的鱼油品质较好。     

太湖白鱼中胶原蛋白的提取及其理化性质分析

从白鱼鱼鳍、鱼鳞、鱼皮、鱼肉、鱼骨、鱼鳔中提取胶原蛋白,研究不同p H条件下胶原蛋白溶解度的变化。分别运用高效液相色谱法、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、酶解肽图分析、差示量热扫描法分析白鱼各部位提取的胶原蛋白的组成、结构以及理化性质。结果表明,白鱼各部位的胶原蛋白在酸性（p H3⁴）条件下具有较好的溶解性,中碱性条件下溶解度骤降。在p H4条件下,鱼皮、鱼鳔中胶原蛋白的提取率高于其他部位,分别达到18.80%和15.95%。白鱼各部位胶原蛋白具有相似的氨基酸组成,蛋白分子中含有1/3左右的甘氨酸,脯氨酸和羟脯氨酸的含量在154.2¹99.0残基/1000个残基之间,亚基分子量相似,存在两条不同的α链（α1和α2）,主要为Ⅰ型胶原蛋白,变性温度在34.16³6.40℃之间。白鱼各部位提取的胶原蛋白在组成、结构和理化性质上具有良好的相似性。      

Location of lipid-soluble selenium in marine fish to the lipoproteins

It has been established that a lipid-soluble selenium compound is enriched in high molecular weight (m.w. ≥5000) extracts from fish. The selenium compound is also enriched in oil extracted from fish by a mixture of non-polar and polar organic solvents (hexane-isopropanol) as compared to the oil extracted with non-polar solvents (hexane) only. When raw fish material is stored it gradually deteriorates and the selenium content in oil produced by boiling of the raw fish material, increases with time. The results indicate that at least part of the lipid-soluble selenium is bound as a lipoprotein.     

Structural Characteristics of Extracted Collagen from Tilapia (Oreochromis mossambicus) Bone: Effects of Ethylenediaminetetraacetic Acid Solution and Hydrochloric Acid Treatment

Desalting is an important process of bone collagen extraction. In this present study, collagens were prepared from tilapia bone using acetic acid and pepsin. The extracted collagen was partially characterized. Prior to extraction, tilapia bone was desalted by soaking in ethylenediaminetetraacetic acid solution and hydrochloric acid. Thermo-gravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy were performed to analyze the structural characteristics. The extracted protein was classified as collagen by Fourier transform infrared spectroscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and circular dichroism. Results showed that desalination with HCl was fast, but collagen yield was low. No acid-soluble collagen and only 0.5% pepsin-soluble collagen were obtained from HCl-treated fish bone. By comparison, the yields of acid-soluble collagen and pepsin-soluble collagen from ethylenediaminetetraacetic acid-treated fish bone were 3.5 and 6.0%, respectively. These values were observed higher than those from HCl-treated fish bone. In HCl-treated fish bone, the properties of collagen, such as amino acid composition, denaturation temperature, and molecular weight distribution, were different from those of collagen in ethylenediaminetetraacetic acid-treated fish bone. Collagens extracted from ethylenediaminetetraacetic acid-treated fish bone showed more integrated secondary structure. Therefore, ethylenediaminetetraacetic acid can be used more effectively than HCl to extract collagen from tilapia bone.     

Comparison of antiatherogenic properties of lipids obtained from wild and cultured sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata)

The aggregatory properties of lipid fractions, obtained from wild and cultured specimens of sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) were studied. The total lipids were extracted and separated into polar and neutral lipids. The polar lipids and neutral lipids were further separated by thin layer chromatography and the fractions obtained were tested for their ability to aggregate platelets or inhibit the platelet-activating factor (PAF)-induced aggregation. The aggregatory properties of the lipid fractions were dependent on the fish species and whether the fish samples were wild or cultured. The lipid fractions extracted from wild gilthead sea bream showed strong aggregatory properties, while the lipid fractions extracted from farmed fish showed strong inhibitory activities. The aggregatory properties of total lipids were mainly attributed to polar lipids while the PAF antagonistic activity was attributed to neutral lipids. The biological activities of such fractions with respect to their aggregatory properties may explain, in part, the protective role of fish consumption against cardiovascular diseases.     

鲤鱼鱼鳞胶原蛋白性质的研究

采用两种不同的脱钙方法,经提取得到两种鲤鱼鱼鳞胶原蛋白,并对其吸水性、吸油性、乳化性等性质进行了研究。采用盐酸脱钙制得的鱼鳞胶原蛋白具有较好的吸水性、保水性和吸油性,用EDTA溶液脱钙制得的鱼鳞胶原蛋白具有较好的起泡性和凝胶性,以上性质均优于商品明胶。该研究为鱼鳞胶原蛋白的进一步利用提供了科学依据。     

Study on the properties of gelatins from skin of carp (Cyprinus carpio) caught in winter and summer season

The objective of this work was to compare the physiochemical (molecular weight distribution and amino acid composition) and rheological (viscosity property, gel strength and melting point) properties of gelatins from skins of carp caught in winter to those obtained for the summer equivalents. Gelatins from winter and summer fish skins were extracted at 60, 70 and 80 °C. SDS-PAGE patterns for gelatins extracted under the same conditions showed that the degradation of gelatins from winter fish skins were more severe than that of the summer ones. The imino acid contents of the winter and summer gelatins extracted at 60 °C were very similar, showing 190 and 188 residues/1000 residues, respectively. The gelatins from summer fish presented higher melting points and gel strengths, as well as better viscosity properties than the winter equivalents (P < 0.05). The differences in the rheological properties between winter and summer gelatins may be explained by different thermostability of interstitial collagen molecules (from which gelatins were derived) in the two seasons.     

Lipid Peroxidation and Phospholipid Hydrolysis in Fish Muscle Microsomes and Frozen Fish

The interaction between lipid peroxidation and phospholipase A₂ was investigated in fish muscle microsomes and frozen fish muscle. Lysophosphatidylcholine (LPC), a phospholipid hydrolysis product produced by the activity of phospholipase A₂, was detected in the lipids extracted from microsomes peroxidized by incubation with NADH and ADP-Fe³⁺. No detectable level of LPC was found in the microsomal lipids when NADH was withdrawn from the reaction mixture nor in the untreated microsomal lipids. LPC level in the lipids extracted from unheated microsomes was considerably higher than that from heat-treated microsomes when both were peroxidized by incubation with ascorbate and Fe³⁺. Phospholipase A₂ was activated by either NADH-dependent or ascorbate-induced lipid peroxidation in vitro. The levels of lipid peroxidation in fish muscle were higher when fish were stored at higher frozen storage temperatures and so were the levels of LPC.     

固相微萃取-气质联用法测定鲫鱼体中挥发性物质

采用固相微萃取法提取,进一步利用GC/MS法对挥发性物质进行了分离鉴定。研究结果表明,利用该方法鉴定出鲫鱼体中的挥发性物质共有23种,且不同鱼体部分其挥发性成分的种类与含量不同,其中鱼鳞、鱼皮、鱼鳃主要挥发性物质为3-甲基-1-丁醇、己醛、辛醇,而鱼肉内挥发性组分较多,1-辛烯-3醇为主要挥发性组分,其余为C4～C8的醇类,为开发新型鱼类脱腥加工技术奠定了基础。     

Sustainable use of marine resources – turning waste into food ingredients

Fish by‐products are considered low value and discarded. With proper handling and processing, fish by‐products may provide high nutritional value to consumers. This study aimed at establishing compositional differences in valuable compounds from fish by‐products of selected species, including Salmon, Flathead, Silver warehou and Barramundi. Simple extraction methods were employed, and obtained fractions were analysed for their chemical and physical properties. The chemical composition of four fish species differed significantly (P < 0.05) with the protein content ranging from 14.7 ± 0.09 to 16.8 ± 0.41%. Adjusting pH to 2.5 yielded two times more of extracted oil than at pH 4.5. Salmon and Barramundi oils contained high amounts of monounsaturated fatty acids (MUFAs) (39–50%), while Silver warehou and Flathead oils contained 46–49% of saturated fatty acids (SFAs). The particle size of the protein fractions was small, ranging from 126.9 to 489.5 nm. Molecular weight of extracted proteins was fish species dependant – Silver warehou and Barramundi samples contained proteins of 250, 120 and 100 kDa, while these bands were absent from Salmon and Flathead samples. The data obtained indicate that extracted fractions from fish by‐products likely have high nutritional value and could find a potential use in food formulations.     

鲢鱼内脏油提取方法的比较研究

为建立鲢鱼内脏油的最佳提取方法及工艺,充分利用鲢鱼资源,以鲢鱼内脏为原材料,分别采用淡碱水解法-钾法和酶解法进行鱼油提取,以鱼油提取率和理化性质进行比较研究。结果表明,钾法提取鲢鱼内脏油的最佳工艺条件为液固比1.5∶1（mL/g）、硝酸钾用量5%、温度70℃、pH7.5、水解时间40min和盐析时间15min,鱼油提取率为87.49%;酶解法提取的最佳工艺条件为pH7、温度50℃、酶解时间2.5h、酶添加量1.5%和液固比1.5∶1,鱼油提取率为90.33%。钾法与酶解法提取的鱼油理化指标分别为:酸值14.58、9.23mg KOH/g,过氧化值3.82、3.47mmol/kg,碘值123.93、127.48g I2/100g,水分及挥发物0.48%、0.32%,不溶性杂质0.13%、0.34%。除不溶性杂质外,其他指标酶解法均优于钾法。酶解法是鲢鱼内脏油提取的较好方法。      

Monitoring of bisphenol-A-diglycidyl-ether (BADGE) in canned fish in oil

A survey at the European level was initiated on the quantification of bisphenol-A-diglycidyl-ether (BADGE) in canned fish in oil in order to assess the exposure of BADGE. A total of 382 canned fish samples were collected from all 15 Member States and Switzerland and analysed for BADGE in fish. The fish was extracted first with hexane and reextracted with acetonitrile, followed by a membrane filtration and reverse phase HPLC analysis with fluorescence detection. The analysis of the fish showed that about 3% of the samples contained BADGE at a level above 1mg/kg. The samples exceeding the limit by a larger margin were mostly from anchovy cans and cans manufactured in 1991-1995.     

Effect of EDTA, HCl, and Citric Acid on Ca Salt Removal from Asian (Silver) Carp Scales Prior to Gelatin Extraction

ABSTRACT:  Pretreatments with different chemicals at different concentrations to remove Ca compounds were studied to determine their effects on gelatin extraction from silver carp ( Hypophthalmichthys molitrix ) scales. During Ca removal with HCl, citric acid, and EDTA, all 3 chemicals were able to decalcify (>90%) scales; however, protein losses with EDTA were lower than with HCl and citric acid ( P  < 0.05), and protein losses with citric acid were lower than with HCl ( P  < 0.05). Ca removal with HCl yielded a solution where 4% to 5% of the protein was Hyp, with estimated gelatin losses from 0.9% to 2.5%. After 0.20 mol/L HCl was used for Ca removal, the extracted gelatin solution was 15.4% of the initial scales weight and gave a gel strength of 128 g. After using 1.2 g/L citric acid for Ca removal, the extracted gelatin solution was only 9% of the scales and the gel strength was 97 g. Using 0.20 mol/L EDTA for Ca removal gave a yield of 22% and a gel strength of 152 g. These data suggest that EDTA at 0.20 mol/L provides the best Ca removal with minimal collagen/gelatin removal (estimated gelatin loss was less than 0.013%) during the Ca removal step, and subsequently gave a high gelatin yield and gel strength. Fish gelatin has generally been extracted from fish skins and occasionally fish bones. This article focuses on removing the Ca compounds in fish scales and then producing fish gelatin with a good gel strength and yield. With further studies, this study may help the fish industry to have a new source of fish gelatin for food and pharmaceutical applications.     

水酶法提取斑点叉尾鮰内脏油的工艺研究

为提高鱼类加工废弃物的综合利用率,以斑点叉尾鮰内脏为原料,采用水酶法制备鱼油。结果表明：水酶法提取鱼油的最佳工艺条件为初始pH7.5、料液比1:1、加酶量3500U/g、酶解温度55℃、酶解时间0.5h,该条件下鱼油的提取率达到80.94%;提取到的鱼油(即粗鱼油)外观呈黄褐色,具有鱼腥味和轻微的酸败味,其过氧化值较低,而酸值相对较高;粗鱼油中的饱和脂肪酸相对含量为19.42%,单不饱和脂肪酸和多不饱和脂肪酸分别为61.76% 和16.83%,Σn-3/Σn-6 的脂肪酸比值达到3.63。表明斑点叉尾鮰内脏是生产鱼油的良好来源。     

Properties of Gelatin Film from Horse Mackerel (Trachurus japonicus) Scale

Optimal conditions for extracting gelatin and preparing gelatin film from horse mackerel scale, such as extraction temperature and time, as well as the protein concentration of film‐forming solutions were investigated. Yields of extracted gelatin at 70 °C, 80 °C, and 90 °C for 15 min to 3 h were 1.08% to 3.45%, depending on the extraction conditions. Among the various extraction times and temperatures, the film from gelatin extracted at 70 °C for 1 h showed the highest tensile strength and elongation at break. Horse mackerel scale gelatin film showed the greatly low water vapor permeability (WVP) compared with mammalian or fish gelatin films, maybe due to its containing a slightly higher level of hydrophobic amino acids (total 653 residues per 1000 residues) than that of mammalian, cold‐water fish and warm‐water fish gelatins. Gelatin films from different preparation conditions showed excellent UV barrier properties at wavelength of 200 nm, although the films were transparent at visible wavelength. As a consequence, it can be suggested that gelatin film from horse mackerel scale extracted at 70 °C for 1 h can be applied to food packaging material due to its lowest WVP value and excellent UV barrier properties.     

几种香辛料对鱼油抗氧化及消臭作用

用乙醇、石油醚分别从辣椒、生姜和香菜中提取抗氧化物质,比较了不同溶剂的提取率和不同提取物对鱼油的抗氧化效果。结果表明,乙醇对三者均有较高的提取率,抗氧化作用以辣椒的乙醇提取物为最强。此外,还初步研究了上述几种香辛料提取物对鱼油的消臭效果。     

ISOLATION OF INTACT TYPE V COLLAGEN FROM FISH INTRAMUSCULAR CONNECTIVE TISSUE

A purification method for intact type V collagen from fish intramuscular connective tissue was developed. Collagens were extracted with 0.5 M acetic acid from fish intramuscular connective tissue. Intact type V collagen could not be isolated by conventional salt fractionation which has been used for isolation of pepsinized collagens. Isolation was achieved by ion-exchange chromatography in the presence of 5 M urea. This is the first report on isolation of intact type V collagen from muscle tissue.     

基于不同提取方法的鮰鱼皮胶原蛋白理化性质的比较研究

本实验以鮰鱼皮为原料,将碱法、盐法、热水法、酸法与酶法提取的胶原蛋白进行理化性质的比较,通过对不同胶原蛋白的氨基酸组成、紫外光谱、傅里叶红外光谱、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodiumdodecyl sulfate-polyacrylamide gelelectrophoresis,SDS-PAGE）、热变性温度、扫描电子显微镜图像以及流变学特性的研究,从分子结构到微观结构对胶原蛋白进行全面解析和比较。结果表明：5 种方法提取的胶原蛋白的紫外光谱与红外光谱都较为相似,为典型的胶原蛋白;碱法、热水法、盐法、酸法和酶法提取的胶原蛋白热变性温度分别为63.21、71.70、49.49、29.8、22 ℃;SDS-PAGE结果显示酸法、酶法、热水法提取的胶原蛋白均属于Ⅰ型胶原蛋白,且较好地保留了蛋白的结构;高效液相色谱显示碱法与盐法提取的胶原蛋白为多肽的形式;通过流变学特性研究发现,热水法提取的胶原蛋白凝胶稳定性最高。由此可见,不同的提取方法对胶原蛋白的氨基酸组成、流变性质、热变性温度以及微观结构均有不同的影响。