Trace metal content in nine species of fish from the Black and Aegean Seas,Turkey

Trace metal content of nine fish species harvested from the Black and Aegean Seas were determined by microwave digestion and atomic absorption spectroscopy (MD–AAS). Verification of the MD–AAS method was demonstrated by analysis of standard reference material (NRCC-DORM-2 dogfish muscle). Trace metal content in fish samples were 0.73–1.83 μg/g for copper, 0.45–0.90 μg/g for cadmium, 0.33–0.93 μg/g for lead, 35.4–106 μg/g for zinc, 1.28–7.40 μg/g for manganese, 68.6–163 μg/g for iron, 0.95–1.98 μg/g for chromium, and 1.92–5.68 μg/g for nickel. The levels of lead and cadmium in fish samples were higher than the recommended legal limits for human consumption.     

Emulsifying properties of proteins extracted from Australian canola meal

Canola protein albumin fraction, globulin fraction, and canola protein isolate (CPI) were compared to commercial soy protein isolate (SPI) in terms of their emulsifying properties at various pH values. The globulin fraction had higher emulsifying capacity (EC), higher emulsifying activity index (EAI), and the droplet size of emulsions it stabilized was consistently smaller irrespective of pH compared to albumin fraction or CPI. In comparison to SPI, globulin fractions also had higher EC at all pH values tested, higher EAI at acidic pH, and smaller or comparable average emulsion droplet size at both pH 4 and 7. The stability of canola protein based emulsions were comparable to those of SPI based emulsions at most pH values (except the emulsion stabilized by the CPI at pH 4), with no significant (p > 0.05) changes in droplet size during storage for up to 7 days at room temperature. These emulsions, however, experienced separation into the emulsion and serum phases after 24 h storage at room temperature with the exception of CPI- and SPI-stabilized emulsions at pH 9. This study demonstrates the comparable emulsifying properties (forming or stabilizing) of some canola proteins to commercially available SPI, suggesting the potential use of canola proteins in food applications.     

菜籽预榨-浸出粕中植酸的提取

为实现菜籽粕的综合开发利用,研究了一种从菜籽预榨-浸出粕中两步提取植酸的工艺.考察了酸洗pH、酸洗时间、碱提pH和碱提乙二胺四乙酸二钠(EDTA)浓度等对植酸提取的影响.将经过复合纤维素酶水解的菜籽粕在pH 5.0和50℃下酸洗3h获得酸洗液,然后用EDTA浓度0.1mol/L的碱性溶液在pH 12.0和50℃下碱提酸沉获得乳清液,经以上两步可将菜籽粕中的植酸基本提取完全.将提取液中的粗植酸经氢氧化钙沉淀并酸化,再经离子交换可获得纯度为69.96％、提取率为58.0％的植酸产品.     

Physicochemical characterisation of raw fish and stickwater from fish meal production

Chemical and microbiological properties of raw fish (RF) and chemical properties of stickwater (SW) samples were studied as a function of the staleness level of the fish. As time elapsed from fish capture increased, the microbial count in RF, volatile nitrogen content in RF and SW, and dissolved solids and dissolved protein in SW, increased. The apparent viscosity of SW increased as the temperature decreased and as the dry solids or suspended matter content increased. The size distribution of suspended particles in SW depended on the sample preparation technique, method used to measure particle size and whether the size distribution was expressed in terms of the weight or population of fractions. The average size (by weight) of suspended solids in SW was 2.5 μm as estimated by electronic counting. The solubility of protein in SW decreased when acid or alkali were added or thermal treatment (1 h at 90°C) applied. A minimal solubility point occurred near pH 5. The molecular weight of most dissolved proteins in SF was 3 kD. SF also contained a small proportion of 67 kD proteins. The significance of this basic characterisation study for the selection of improved processes for stickwater recovery is discussed.     

库拉索芦荟皮中果胶提取工艺的优化研究

以库拉索芦荟(Aloe barbadensis Mill)为原料,采用酸水解乙醇沉淀的方法提取皮和肉中的果胶。主要从提取温度、提取时间、提取液pH以及料液比等因素进行考察,分别对芦荟皮和芦荟肉进行果胶提取实验,比较库拉索芦荟皮和芦荟肉中果胶含量,利用单因素实验和L9(34)正交实验优化芦荟果胶提取的工艺参数。最终本实验确定芦荟皮中果胶的最佳提取工艺条件为:提取温度80℃,提取时间100min,提取液pH2.5,料液比1:15,果胶产量为0.84g/20g,即得率为4.2%,而芦荟果肉中不含有果胶。      

真空提取核桃粕多酚的抗氧化活性研究

目的 探究真空提取的核桃粕(walnut meal)多酚的抗氧化活性。方法 以非真空条件下提取的多酚为对照,采用超声波辅助真空法提取核桃粕多酚,用HPD-100型大孔树脂对多酚进行纯化,福林酚(Folin-Ciocalte)法测定多酚含量,通过试剂盒检测多酚对1,1-二苯基-2-苦基肼自由基(1,1-diphenyl-2-picrylhydrazyl,DPPH)、超氧阴离子自由基的清除率及Fe³⁺还原能力(ferric reducing antioxidant power,FRAP)来评价其体外抗氧化活性,用cck8(cell countingkit-8)法测定不同浓度的核桃粕多酚对HepG2细胞的毒性作用,确定3个无毒性作用浓度,以770μmol/L的H₂O₂诱导HepG2细胞建立氧化应激损伤模型,通过测定HepG2细胞中丙二醛(malonicdialdehyde, MDA)含量、超氧化物歧化酶(superoxide dismutase, SOD)活力、谷胱甘肽(glutathione, GSH)含量探究12.5、25...     

Gelling properties of protein fractions and protein isolate extracted from Australian canola meal

Gelling properties of canola albumin and globulin fractions, and canola protein isolate (CPI) were examined in this study. The effects of pH and salt concentration on canola protein gelling properties were studied primarily by means of dynamic oscillatory rheology and gel texture analysis. The findings were supported by confocal laser scanning microscopy (CLSM) images of the gels, isoelectric point, and solubility measurement data. All canola proteins showed typical heat-set gel protein profiles. Gels formed at higher pH had better gelling properties including higher overall resistance to deformation (G*), higher gel elasticity (low tan δ ), higher fracture stress and firmness, and denser gel microstructure. Isoelectric points of canola proteins used in this study were in the range of pH 3.0–4.7 where low protein solubility was observed. The albumin fraction was able to form a very weak gel at pH 4, whereas the globulin fraction and CPI precipitated due to loss of protein surface charge. The effects of NaCl on gelling were protein sample dependent. The presence of NaCl negatively affected gelling properties of albumin and globulin fractions, with decreases in overall resistance to deformation (G*), and fracture stress and firmness, but positively affected CPI gels in the same aspects. The elasticity (tan δ) of all canola protein gels remained constant in the presence of NaCl. Frequency sweep analysis revealed that the albumin fraction and CPI formed weak gels, whereas the globulin fraction formed a strong gel. Strain sweep analysis further confirmed that the globulin fraction formed a stronger gel with a critical strain of at least 10%. This study demonstrates the high potential of canola proteins, particularly the globulin fraction, as a prospective gelling agent.     

Toxicity of water extracted rapeseed meal in the rat

The toxic effect of different concentrations of “detoxified” rapeseed meal (DRSM) obtained by 2 h lixiviation was studied. This preparation contained 0.02 % oxazolidinethiones (VTO) and no detectable isothiocyanates (ITC). It was fed for 4 weeks to weanling rats in amounts that provided from 0 to 100% of total dietary protein. The control diet provided 20% protein from casein. Another control group was fed crude rapeseed meal (RSM) to the same protein level. Growth rates and protein efficiency ratio (PER) were similar in rats fed DRSM and casein diets. The substitution of casein by increasing levels of DRSM did not modify PER. The weight of the liver, thyroid, heart, spleen, adrenals and kidneys was normal. In animals fed DRSM no histological changes were detected in the liver. The thyroid exhibited changes similar to, but of lesser severity than in animals fed crude RSM. It is suggested that other toxic compound(s) may be present in rapeseed meal that are not extractable by lixiviation. The need of further investigations of the effect of this “detoxified” product including functional studies before its extensive inclusion in animal or human diets is emphasised.     

Studies on fish protein concentrate and fish meal from river Nile bolti fish (Tilapia nilotica)

Fish protein concentrate (FPC) from river Nile bolti fish (Tilapia nilotica) was prepared and compared with commercial FPC and fresh bolti fish flesh. Fish meal (FM) from bolti fish offals was prepared and compared with commercial FM and also fresh bolti fish flesh. FPC from bolti fish showed a higher crude protein content but less fat, ash, calcium and sand than the commercial sample, while FM from bolti fish showed a higher content of ash and phosphorus than commercial FM but was nearly similar in crude protein, fat, calcium and sodium chloride. FPC from bolti fish had a higher content of lysine, arginine, aspartic acid, glycine and glutamic acid and a lower content of the other free amino acids. The bolti fish FM had a lower content of total amino acids and the contents of the free amino acids cysteine, glycine, aspartic acid, serine, alanine, valine, and methionine increased slightly. The yield was 12% for FPC and 19.5% for FM. Coliform bacteria were not present in both FPC and FM from bolti fish. Low moisture contents of FPC and FM were essential for preventing microbiol growth and to attain a good keeping quality. The FPC and FM from bolti fish reached moisture equilibrium and stopped increasing in weight within 144 to 192 h.     

Physicochemical and emulsifying properties of protein extracted from soybean meal assisted by steam flash-explosion

The conventional alkaline aqueous extraction is not effective in promoting maximum protein yield from soybean meal (SBM). In this study, the steam flash-explosion (SFE) treatment was firstly employed to significantly improve the protein yield, while the protein content of soy protein isolate (SPI) decreased, concomitant with increase in carbon content of SPI. The SFE treatment led to the dissociation of insoluble protein aggregates in SBM, with subsequent increase of soluble protein aggregates formed via on-disulfide covalent bonds. The covalent coupling of the carbohydrate to the protein during SFE treatment can contribute to the dissolubility of protein and the formation of protein aggregates. After SFE treatment, surface hydrophobicity of SPI was decreased, however the emulsifying properties were improved. The emulsifying activity index and emulsifying stability index were improved to 41.94 m²/g and 35.27 min under 1.3 MPa, 180 s treatment condition. It indicated that compared to surface hydrophobicity, changes of other aspects of protein structure including the covalent coupling of carbohydrate to protein were the predominant factors that ruled the emulsifying property of protein.Industrial relevanceThe steam flash-explosion treatment (SFE) is an eco-friendly, low-energy and non-traditional technology, which could be performed on a large scale for the industry. The SFE treatment can effectively change the physicochemical properties of protein resulting in significant increase of protein yield and improvement in emulsifying properties of protein. After SFE treatment, the protein from heat-denatured soybean meal can be refunctionalized for application in food industry.     

Detoxification and nutritional evaluation of solvent extracted Egyptian cottonseed meal

Attempts for degossypolization of the solvent extracted Egyptian cottonseed meal (CSM) and evaluation of its nutritional value as a possible protein supplement for human feeding were undertaken. Three methods were applied for degossypolization: Steaming, addition of iron(II)-sulphate dihydrate, and steaming after addition of iron(II)-sulphate dihydrate. Steaming was done for varying periods of time. Nutritional evaluation was undertaken by chemical analysis and by feeding experiments. Chemically, the third method for degossypolization was the most effective. Feed efficiency and protein efficiency for diets containing 15 and 10% levels of CSM protein indicated that all treatments used for detoxification caused a decrease in diet and protein quality. Diets containing iron-supplemented CSM at the same level were the best of all. Mixing CSM with casein to form a diet containing 10% protein increases the protein quality of both casein and CSM.     

Biogenic amine contents in fish and fish preserves

A method developed on the basis of highly efficient liquid chromatography of dansyl derivatives was used to study the content of biogenic amines (tyramine, histamine, cadaverine, putrescine, spermine and spermidine) in fish and canned fish. It was found that only 7 out of 149 samples contained histamine levels exceeding maximum permissible concentration (salted herring, smoked sardines, and salted Siberian salmon). No correlation was recorded between the increase of spermine content and spermidine.     

Blood amino acids and milk composition from cows fed soybean meal, fish meal, or both

Twelve multiparous Holstein cows at 48 +/- 8 d in milk were used in a 4 x 4 Latin square with 21-d periods to determine the effect on feed intake, milk yield, milk composition, and blood amino acids when soybean meal was replaced with fish meal. Fish meal substituted for soybean meal on an isonitrogenous basis at 0, 25, 50, and 100% of supplemental protein. Total mixed diets were (dry matter basis) 25% corn silage, 25% alfalfa hay, and 50% concentrate mix. Intake of dry matter (27.9, 27.8, 26.1, and 25.8 kg/d for diets 1 to 4, respectively) was similar for all diets. Milk yield (37.5, 37.8, 37.2, and 37.7 kg/d) was not affected by diets. Milk protein percentages (3.23, 3.24, 3.31, and 3.35) increased with 100% fish meal supplementation and tended to be higher, with 50% fish meal supplementation compared with 100% soybean meal diet. Milk fat percentages (3.18, 2.99, 3.04, and 2.87) and yields were lower with the 100% fish meal than with the 100% soybean meal diet. Molar proportions of ruminal volatile fatty acids and ammonia were not greatly affected by diet. Fish meal supplementation slightly improved Met status, as shown when blood amino acid data were evaluated. Both extraction efficiency and transfer efficiency of amino acids from the blood by the mammary gland indicated that Met, Lys, and Phe were the most limiting amino acids in all diets. Replacing as much as 50 or 100% of dietary soybean meal with fish meal may improve the amino acid balance and increase the protein content in milk; however, feeding 100% fish meal will likely decrease milk fat percentages.     

Determination of protein in fish meal

A comparison of the Kjeldahl and Lowry methods for the determination of protein in fish meal has been made. The values obtained with the rapid colorimetric Lowry method, using extracts of total fish meal proteins, were lower than those obtained by the Kjeldahl method. For fish meal from different species the general factor 1.19±0.03 (confidence limit for P<0.01) may be used to convert protein values obtained by the Lowry method into protein values obtained by the Kjeldahl method.     

Reduction of lipids in fish meal prepared from fish waste by a yeast Yarrowia lipolytica

The high lipid content in fish waste is one of the reasons why fish meal made from fish waste is commercially rated as low grade meal. Microorganisms which have the ability to reduce crude lipids from samples of minced fish in solid-state fermentation were screened and a strain of Yarrowia lipolytica showed the highest efficiency for reducing the lipids by 29%. The lipid reduction by this strain was especially affected by the ratio of surface area to the weight in the fermented mince samples and by the water content, suggesting the importance of the oxygen supply. In the fermentation with intermittent mixing during 96 h incubation, reduction efficiency for crude lipids came to 46% but that for protein was less than 1%. With the fermentation, 41.5 g of crude lipids in 1 kg of the minces were estimated to be reduced to 22.4 g, indicating increase of protein content in the final product. Furthermore, the carbonyl value which is an indicator of lipid oxidation was relatively suppressed by the fermentation. These results suggest that the fermentation can improve the quality of fish meal from fish waste which is rich of lipids.     

Trace metals in muscle tissue of fish taken from the southern Baltic

The determination of Fe, Mn, Ni, Pb, Cu, Co, Zn and Cd was investigated on 123 samples of muscle tissue of cod, herring, sprat and some other species of fish caught in 1981 in the southern Baltic Sea. The ranges and mean levels of metals recorded in this paper are compared with values reported previously by other authors for cod, herring and sprat from different regions of the Baltic Sea. The correlation coefficients between the metal concentrations in cod and herring muscles were calculated. The species-dependent changes of some metals in species analysed were observed.     

Enrichment of γ-linolenic acid in the lipid extracted from Mucor zychae MTCC 5420

The aim of this work was to study the enrichment of the Gamma linolenic acid (GLA) content of lipid extracted from Mucor zychae by employing a low-temperature urea crystallization process. GLA, a polyunsaturated fatty acid has been reported to have many health benefits and has potential implications in food and pharmaceutical industry. Lipids extracted from the mycelia of fermented broth were transesterfied and analysed by gas chromatography. Results showed that the fungal oil contained (%) myristic acid (1.2), palmitic acid (35.3), palmitoleic acid (3.7), stearic acid (2.7), oleic acid (39.2), linoleic acid (6.4) and gamma linolenic acid (8.7). After the first step of crystallization, the percentage of GLA enriched in the total lipid was increased to 63.5. The concentration of GLA further increased when the enriched lipid sample was subjected to urea crystallization for the second time. GLA percentage increased from 63.5 to 92.7, and recovery of GLA was 63%. By altering the ratio of fatty acid ethyl ester:urea, the concentration characteristics and the recovery of GLA also varied; highest recovery of GLA (69%) was obtained when, the above ratio was 1:3. Furthermore, GLA recovery was in considerable amounts at 0 °C crystallization.     

两种溶剂萃取棉籽油和棉籽粕的质量比较

利用正己烷和异丙醇作溶剂,分别萃取棉籽仁得到棉籽油和棉籽粕.对棉籽油的理化指标进行测定,结果表明两种不同溶剂萃取得到的棉籽油在理化指标上存在一定的差异.分析所得棉籽粕的蛋白含量和功能特性,结果表明正己烷萃取的棉籽粕中粗蛋白含量和水溶性蛋白含量均低于异丙醇萃取的棉籽粕;正己烷萃取的棉籽粕吸油性、泡沫稳定性小于异丙醇萃取的棉籽粕,但是吸水性、乳化性、乳化稳定性和起泡性却高于异丙醇萃取的棉籽粕.分析游离棉酚含量时,发现异丙醇萃取的棉籽油中游离棉酚(FGP)含量高于正己烷萃取的棉籽油.用异丙醇萃取的棉籽粕中FGP含量在国家标准规定的安全使用限量范围内,用作饲料时不需再增加脱毒工艺.