防止白鲢鱼糜蛋白质冷冻变性的研究

用正交试验Ｌ９（３＾３）法研究了白链鱼糜蛋白经漂洗后，添加食品磷酸盐和蔗糖作为抗冻剂对防止冷冻变性的影响。结果显示：漂洗液的盐分浓度越低，鱼糜中蔗糖含量越高，蛋白质冷冻变性程度越小。添加食品磷酸盐对漂洗和未漂洗鱼糜的影响有所不同。此外，在无抗冻剂条件下冷冻，漂洗鱼糜蛋白质的变性程度大于未漂洗鱼糜，而抗冻剂在提高漂洗鱼糜蛋白质抗冷冻变性的效果比未漂洗鱼糜要明显。     

Effect of pretreatments on chemical compositions of mince from Nile tilapia (Oreochromis niloticus) and fishy odor development in protein hydrolysate

Fish protein hydrolysates (FPH) have gained increasing attention as nutritious fish products. Lipid oxidation associated with fishy odor in FPH limits its utility. Thus, an appropriate pretreatment of fish mince prior to hydrolysis by lowering pro-oxidants and lipid substrates could tackle such a problem. Different pretreatments of Nile tilapia minces including (1) washing (W), (2) washing and membrane removal (W-MR), and (3) washing/membrane removal followed by acid or alkaline solubilization (W-MR-Ac or W-MR-Al) were conducted prior to hydrolysis. During the hydrolysis process, degree of hydrolysis (DH) and chemical changes were monitored. Color and sensory properties of milk fortified with hydrolysates prepared from mince without and with pretreatment were also determined. Among the pretreated mince samples, W-MR-Al contained the lowest remaining myoglobin and heme iron contents and also showed the lowest total lipid and phospholipid contents (P?<?0.05). When mince and W-MR-Al were hydrolyzed using Alcalase for up to 120?min, higher DH were found in W-MR-Al. Furthermore, lower peroxide values, thiobarbituric acid reactive substances, and non-heme iron contents of hydrolysates from W-MR-Al were also observed (P?<?0.05). When FPH powder from mince and W-MR-Al (0.3% to 0.5%) were fortified in milk, the former yielded a lower likeness score (P?<?0.05) at all levels used. The addition of the latter up to 0.5% had no effect on likeness of all attributes, compared with control (without FPH). An appropriate pretreatment of mince was a promising approach to lower fishy odor problem, caused by lipid oxidation in FPH.     

Assessing the Antioxidant Activity of the Ultrafiltration Fractions From Silver Carp Protein Hydrolysate by Different Antioxidant Methods

Silver carp protein hydrolysate (SH) was fractionated by 5- and 1-kDa cutoff ultrafiltration (UF) membrane, and three ultrafiltrates were obtained: SHI (>5 kDa), SHII (1–5 kDa), and SHIII (<1 kDa) which were screened for antioxidant activity by five in vitro assays. The SHIII showed higher 2, 2-azobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) values, inhibiting effects for liposome oxidation induced by Fe³⁺/V_C. The SHII showed higher ferric reducing power (FRAP) and inhibiting effects for liposome oxidation induced by 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). However, the SHI showed the highest 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging activity. Therefore, the antioxidant activity of silver carp protein hydrolysates was mainly associated with their molecular weight distribution, and the antioxidant assays used to test different samples gave comparable results.     

Effect of a Previous Washing Step with Tannic Acid on the Quality of Minced Horse Mackerel (Trachurus trachurus) During Frozen Storage

Fatty fish have been recognized as potential raw material for production of minced meat; however, they are prone to oxidation and further deterioration. In the present study, the effect of washing and antioxidant (tannic acid) treatment on the quality of minced meat of Trachurus trachurus (horse mackerel) during frozen storage was observed. Minced meat of Trachurus trachurus was divided into three lots (T0, T1, and T2). T1 was washed with cold water, T2 with cold water containing tannic acid (100 mg/kg), and T0 was not washed. All the lots were frozen at ?40°C and stored at ?20 ± 2°C for 125 days and were subjected to biochemical, microbiological, and sensory evaluation at regular intervals of 25 days. The antioxidant treatment with tannic acid at the dosage used was found effective in minimizing the rancidity problems of minced meat (T2), compared to T0 and T1. During the whole period of storage, samples from T2 showed good quality in terms of microbiological, biochemical, and sensory analysis compared to T1 and T0.     

Metabolism of fatty acids in fish: III. Combined effect of environmental temperature and diet on formation and deposition of fatty acids in the carp,Cyprinus carpio Linnaeus 1758

Formation and deposition of fatty acids in carp maintained on diets differing in total fat as well as linolenic acid content was investigated by following the incorporation of (1-¹⁴C)-acetate into liver total- and phospholipid fatty acids at two extreme temperatures (5° and 25°C). Excess dietary linolenic acid was deposited in triglycerides but not in phospholipids. The formation and level of phospholipid docosahexenoic acid was, however, dependent on the amount of linolenic acid in the diet. Despite the vast quantities of ingested linolenic acid, the carp on diets containing sufficient essential fatty acid maintained similar membrane fluidities as judged from the ratio of saturated to unsaturated fatty acids. Decrease of the environmental temperature brought about a reduction in the rate of formation of palmitic acid and an increase in the rate of formation of docosahexenoic acid in carp receiving sufficient essential fatty acid. Consequently, the level of palmitic acid decreased and that of docosahexenoic acid increased in the liver phospholipids in carp and a number of other fish species. Essential fatty acid deficient carp were unable to increase the rate of production of long chain polyunsaturated fatty acids upon exposure to cold. The results are discussed from the point of view of adaptation of membrane fluidity to the temperature by fish, and the importance of docosahexenoic acid in this process is emphasized.     

Antioxidant and ACE Inhibitory Activities of Kawakawa (Euthynnus affinis) Protein Hydrolysate Produced by Skipjack Tuna Pepsin

ABSTRACT

Pepsin enzyme from skipjack tuna was extracted for the production of kawakawa (Euthynnus affinis) fish protein hydrolysate. Using ultra-fractionation, Kawakawa protein hydrolysates were separated into four different fractions, including fractioned protein hydrolysate I (FPH I) (< 1 kDa), FPH-II (1–3 kDa), FPH-III (3–10 kDa), and FPH-IV (> 10 kDa). The antioxidant activity was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, inhibition of linoleic acid oxidation, reducing power tests, and chelating activity of metal ions. Results indicated that FPH II fraction peptides had higher antioxidant activity in comparison with the other fractions, followed by FPH I. Further, the fractions were evaluated for angiotensin converting enzyme (ACE) inhibition, and IC₅₀ value ranged from 0.45 to 1.86 mg/ml with higher activity in FPH I (IC₅₀ 0.45). Finally, the amino acid profile of different fractions was analyzed. The fractions exhibited significant amounts of hydrophobic amino acids, which could perform as hydrogen donors, frustrate the free radicals, and inhibit the ACE. The recovered pepsin from the viscera was used to produce hydrolysates with good biological activities. Peptides lower than 3 KDa had antioxidant activity as positive controls and significant ACE activity. These are very important findings that could be used to conduct further research in a preclinical study of these peptides.     

关于鱼糜在冷藏过程中蛋白质变性的研究——冷藏过程中Ca++-ATPase活性变化的探讨

本文就草鱼鱼糜在冷藏过程中肌原纤维蛋白Ca^ -ATPase活性的变化及几种因素对其活性的影响作了初步探讨。并与VBN值的变化作了比较。冷藏过程中，鱼糜的肌原纤维蛋白Ca^ -ATPase活性变化明显，而VBN值变化不大，因此可用肌原纤维蛋白Ca^ -ATPase活性的大小来鉴别冷藏前期鱼糜蛋白质的变性程度。几种因素对蛋白质变性具有不同程度的影响。对于已腐败的鱼糜，不宜用鱼糜肌原纤维蛋白Ca^ -ATPase活性来鉴定其品质的优劣。     

Antioxidative role of cerium against the toxicity of lead in the liver of silver crucian carp

The antioxidative role of cerium was investigated in the liver of silver crucian carp injected with lead. The fish were intraperitoneally injected with 10, 20, or 30 mg/kg wet weight PbCl₂. After a 14-day period of incubation, 35 animals were injected with a solution of 1.5 mg/kg wet weight CeCl₃. After 42 days, the wet weight and the liver weight of the fish were weighed, and the oxidative stress of the fish liver was estimated by assaying lipid peroxide, superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione, ascorbic acid, and reactive oxygen species (ROS). The results show that Ce³⁺ could decrease ROS accumulation, relieve the inhibition of the activities of the antioxidant enzyme and the reduction of antioxidants in fish liver caused by Pb²⁺, and decrease the enhancement of hepatosomatic index of fish under various Pb²⁺ dosages.     

Fatty acid composition of the ingested food only slightly affects physicochemical properties of liver total phospholipids and plasma membranes in cold-adapted freshwater fish

The fatty acid content, fatty acid molecular species composition, and fluidity of phospholipid vesicles and plasma membranes of livers of fish feeding on phytoplankton (silver carp, Hypophthalmichtys molitrix), zooplankton, (big head carp, Hypophtalmitrix nobilis), higher plants, (grass carp, Ctenopharyngodon idella), and omnivorous fish, (common carp, Cyprinus carpio), adapted to reduced temperatures, was determined. Levels of long chain polyunsaturated fatty acids (PUFAs) were highest in silver and big head carp and lowest in common carp. Differences in long chain PUFAs were poorly reflected in fluidity, determined either by fluorescence anizotropy of 1,6-diphenyl 1,3,5-hexatriene or rotational correlation time of 16-doxyl- stearic acid, of phospholipid vesicles. Phospholipid vesicles of C. caripo and C. idella proved to be slightly more rigid than of H. molitrix and H. nobilis below ca. 15 °C. These differences were not seen with isolated plasma membranes assessed with 1,6-diphenyl 1,3,5-hexatriene. Using electron spin resonance spectroscopy plasma membranes from H. molitrix proved to be more fluid than those from C. carpio below ca. 15 °C. Phosphatidylethanolamines were abundant in 1-monounsaturated, 2-polyunsaturated (18:1/22:6, 18:1/20:4) species with H. molitrix and H. nobilis more rich in these species than C. carpio and C. idella. It is suggested that differences in fluidities of phospholipid vesicles below 15 °C is due to differences in levels of the above molecular species. In native membranes these differences may be masked by proteins and other membrane components. It is also suggested that it is not the fatty acid composition of the ingested food but the specific response of the fish to temperature that is the most important factor controlling the physicochemical properties of membranes during thermal adaptation.     

Evaluation of the Antioxidant and Antimicrobial Activity of Protein Hydrolysates and Peptide Fractions Derived from Colossoma macropomum and Their Effect on Ground Beef Lipid Oxidation

The objective of this study was to obtain protein hydrolysate from the mechanically separated meat of blackfin pacu to evaluate the influence by ultrafiltration in the antioxidant and antimicrobial activities of the peptide fractions obtained and to apply in ground beef to evaluate the lipid stability. The enzymatic hydrolysis was performed using the enzyme Protamex (pH 7.0, 60°C) for 240 min. The protein hydrolysate was fractionated by ultrafiltration. Then, the antioxidant capacity of the protein hydrolysate and the peptide fractions were evaluated in vitro by the methods of 2,2’-azinobis (3-ethylbenzothiazoline sulfonic acid) radical capture, 2,2-diphenyl-1-picrylhydrazyl radical-scavenging assay, reducing power, and hydroxyl radical scavenging activity. The antimicrobial activity of the samples was evaluated by disc-diffusion against Staphylococcus aureus and Escherichia coli. After evaluation, the peptide fractions did not present higher bioactivities than that shown for the hydrolysate. The protein hydrolysate was applied to ground beef, where the substances reactive to thiobarbituric acid and color were evaluated during 7 days of storage at 4°C. Lipid oxidation was reduced up to 60.9% and there was no modification of the natural coloration. Thus, the protein hydrolysate can be used as an alternative source of antioxidant for the preservation of refrigerated meats.     

Purification and Antioxidant Property of Antioxidative Oligopeptide from Short-Necked Clam (Ruditapes philippinarum) Hydrolysate In Vitro

Short-necked clam (Ruditapes philippinarum) muscle was hydrolyzed with trypsin, and the antioxidant activities of isolated peptides were investigated. The hydrolysate was fractionated by chromatographic methods using Sephadex G-25 gel filtration and Hypersil BDS C18 reversed phase high performance liquid chromatography (RP-HPLC). The antioxidant activities of the hydrolysate were determined by measuring 1,1-diphenyl-2-picrylhydrazyl (DPPH), reducing power assay, and the protective effect against hydroxyl-radical-induced DNA damage. The amino acid sequence of the purified antioxidant oligopeptide was found to be Gly-Asp-Gln-Gln-Lys.     

鱼肉酶解物及壳聚糖对鲤鱼涂膜保鲜效果的研究

以感官评分、挥发性盐基氮、菌落总数、K值为指标,研究比较了鱼肉酶解物和壳聚糖为原料的涂膜液对鲤(Cyprinus carpio)(4℃)冷藏过程中品质变化的影响。结果显示:贮藏期间,对照组的感官评分显著低于各涂膜组(P<0.05)。贮藏前8 d,涂膜组能够显著抑制K值的升高(P<0.05)。鱼肉酶解物和壳聚糖涂膜组均能够显著抑制细菌的生长,而贮藏2～6 d内鱼肉酶解物涂膜鲤鱼的菌落总数显著低于壳聚糖涂膜组(P<0.05)。贮藏后期,鱼肉酶解物组能延缓TVB-N值的升高,壳聚糖涂膜组能够显著抑制TVB-N值的升高(P<0.05)。鱼肉酶解物可作为一种新的可食性涂膜材料,用于延长鲤鱼的贮藏期。     

The extracts of Angelica sinensis inhibit lipid oxidation in fish erythrocytes and improve growth,digestive, absorptive and antioxidant capacity in juvenile Jian carp (Cyprinus carpio var. Jian)

The study explored the effects of ethyl ether extract, ethyl acetate extract (EAE), acetone extract, ethanol extract and aqueous extract of Angelica sinensis (EAs) and ethoxyquin (EQ) on lipid oxidation in erythrocytes and growth, digestive, absorptive and antioxidant capacity in carp (Cyprinus carpio var. Jian). The results indicated that EAs and EQ respectively at the concentrations of 0.5 and 0.25 mg/ml suppressed lipid oxidation by decreasing the generation of ROS and restoring the activities of antioxidants in hydroxyl radical‐treated erythrocytes. Of all of the examined EAs, EAE showed the strongest protective effects against lipid oxidation in carp erythrocytes. The antioxidant effects of EQ at the concentration of 0.25 mg/ml were stronger than that of EAE at the concentration of 0.5 mg/ml in fish erythrocytes. The antioxidative activities of EAs in carp erythrocytes were positively correlated with their phenols content. Moreover, dietary EAE raised growth performance in fish. The appropriate concentration of EAE for the growth of fish was estimated to be 3.544 g/kg diet. Dietary EAE increased digestive and absorptive capacity in carp and improved antioxidant capacity in copper‐treated carp. So, EAE could be used as a potential natural antioxidant and inhibitor of copper stress in fish.     

Gelation Characteristics of Mince and Washed Mince From Small-Scale Mud Carp and Common Carp

Small-scale mud carp (SC, Cirrhina microlepis) and common carp (CC, Cyprinus carpio) are underutilized freshwater fish. The objective of this study was to elucidate the gel-forming ability of mince and washed mince from these species in relation to washing cycles and CaCl₂ addition. Protein loss of up to 67% was observed after three-washing cycles of both species, rendering relatively low yield. About 85–90% of total fat was removed from SC flesh after three-washing cycles, but only two-washing cycles were sufficient for fat removal in CC mince. Mince and washed mince of both species did not exhibit severe proteolysis with low autolytic activity at 65°C. SC exhibited superior gel-forming ability to CC. Two- and three-washing cycles in conjunction with a 40°C-preincubation resulted in the highest textural properties of SC and CC, respectively. CaCl₂ increased the breaking force of CC and SC mince gels up to 65 and 95% at 0.3 and 0.5% CaCl₂, respectively, as compared to without CaCl₂. However, it showed negative effects on surimi gels of both species. Both SC and CC are potential freshwater fish resources for mince and washed mince production with reasonable good gel-forming ability.     

Effect of size‐fractionated fish protein hydrolysate on growth and feed utilization of turbot (Scophthalmus maximus L.)

Four experimental diets were fed to turbot to examine the effect of fish hydrolysate and ultra‐filtered fish hydrolysate on growth performance, feed utilization and non‐specific immune response. Fish hydrolysate was produced by enzymatic treatment and size fractionated using ultra‐filtration (UF). The permeate (molecular weight <1000 Da) after UF and the non‐ultra‐filtered fish hydrolysate (NUF) were tested as feed ingredients. Diets UF1, UF2 contained 3.7%, 1.2% ultra‐filtered fish hydrolysate to replace fish meal protein respectively. The diets UF1, NUF were identical in composition except that the molecular weight of fish hydrolysate in the diet. Fish meal was used in the control diet. All diets were made equal in protein, lipid and energy. Each experimental diet was fed to juvenile turbot (27.87 ± 0.04 g) in triplicate for 8 weeks. Results of this study indicate that the best overall growth and feed utilization of turbot juveniles were obtained with a diet containing higher dose of the small molecular weight compounds in fish hydrolysate. Acid phosphatase, alkaline phosphatase, lysozyme and superoxide dismutase activity in serum were not affected by diet. Total antioxidant capacity was improved with increasing level of low molecule weight fish hydrolysate (UF1).     

Effects of different dietary selenium sources (sodium selenite,selenomethionine and nanoselenium) on growth performance,muscle composition,blood enzymes and antioxidant status of common carp (Cyprinus carpio)

This experiment was conducted to compare the effects of different sources of selenium (Se) on growth, muscle Se concentration, muscle proximate composition, blood enzymes and antioxidant status of common carp, Cyprinus carpio. Organic Se (selenomethionine, SeMet), inorganic Se (sodium selenite, Na₂SeO₃), or nanoselenium were each added to the basal diet at 0.7 mg Se kg^?1 diet. Four groups of fish with an average weight of 9.69 ± 0.12 g were fed one of the experimental diets for 8 weeks. Nano‐Se diet resulted in better growth performance (P < 0.05). Fish fed with Se‐supplemented diets showed a higher (P < 0.05) Se content in the muscle and liver tissues. Fish fed nano‐Se had the highest liver glutathione peroxidase, superoxide dismutase and catalase activities (P < 0.05). Liver malondialdehyde level was significantly (P < 0.05) lower in fish fed on SeMet and nano‐Se diets as compared to control. The carp fed on nano‐Se diet had the lowest values of aspartate transaminase and alanine transaminase. Lactate dehydrogenase activity was significantly lower in fish fed on SeMet and nano‐Se diets. This study shows that nano‐Se acts more efficiently on growth performance and antioxidant defence system of common carp than organic and inorganic sources of Se.     

鲢肌肉脂肪酸分离方法效果比较及组成特征分析

采用了三种不同方法,即超声波提取法、索氏提取法和氯仿-甲醇法,从鲢(Hypophthalmichys molitrix)肌肉中提取鱼油,继而进行酸性或碱性甲酯化,经气相色谱/质谱联用技术,对其脂肪酸组成特征进行了定性和定量分析。结果显示:鲢肌肉检测出25种脂肪酸,其中包括7种饱和脂肪酸,8种单不饱和脂肪酸和10种多不饱和脂肪酸。获得不饱和脂肪酸含量占总脂肪酸含量分别为41.39%、36.15%、33.55%,可见三种分离方法间存在明显分离效果差异。因此得出石油醚作溶剂的超声波萃取法是提取和分析鱼类脂肪酸较理想的方法。     

The effect of dietary folic acid on flesh quality and muscle antioxidant status referring to Nrf2 signalling pathway in young grass carp (Ctenopharyngodon idella)

To investigate the effect of dietary folic acid on fish flesh quality, muscle antioxidant status and the potential mechanism, young grass carp (Ctenopharyngodon idella) were fed diets containing 0.10–3.12 mg/kg diet of folic acid for 8 weeks. The results showed that optimum folic acid increased muscle contents of protein, lipid, pH, shear force, amino acids, unsaturated fatty acids, hydroxyproline and glutathione, whereas contents of moisture, cooking loss, lactate and saturated fatty acids and cathepsin L activity showed an opposite trend (p < .05). Moreover, optimum folic acid elevated antioxidant enzyme activities and mRNA levels, as well as NF‐E2‐related factor 2 and casein kinase 2 mRNA levels (p < .05). However, optimum folic acid decreased reactive oxygen species (ROS) content and Kelch‐like ECH‐associated protein 1a (Keap1a) and Keap1b mRNA levels (p < .05). Interestingly, excess folic acid induced negative effects on above‐mentioned parameters (p < .05). Summarily, this study indicated that optimum folic acid improved fish flesh quality and muscle antioxidant system associated with Nrf2‐Keap1 pathway. Based on muscle cathepsin L activity and ROS content, the folic acid requirements for young grass carp were 1.87 and 1.80 mg/kg diet, respectively, regarding to the flesh quality and antioxidant status.     

Evaluation of the Antioxidant Activity In Vitro and in Hippocampal HT-22 Cells System of Protein Hydrolysates of Common Carp (Cyprinus carpio) By-Product

Fish processing by-products may become more than 50% of the starting material. If mismanaged, these large quantities of discarded fish can create serious pollution problems and can also generate cost associated with their disposal. Enzymatic hydrolysis is one of the techniques that is currently being developed in order to recover and add value to these biomolecules. There is an increasing interest in natural antioxidants that are safer for consumers compared with synthetic antioxidants. In this study, common carp by-product was hydrolyzed using the enzymes Alcalase (A) and Protamex (P) to reach degrees of hydrolysis (DH) of 10 and 15%, respectively. Antioxidant capacity against peroxyl radicals (ACAP); 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging; and the measurement of intracellular reactive oxygen species (ROS) concentration after exposure to common carp protein hydrolysates were investigated. The results revealed that the hydrolysate A15 exhibited significantly (p < 0.05) higher antioxidant activity against the DPPH radical. A15 showed the highest in vitro antioxidant competence against peroxyl radicals, whereas P15 showed the lowest activity against peroxyl radicals (p < 0.05). Hydrolysates having the highest and the lowest in vitro antioxidant activity (A15 and P15, respectively) were selected for the determination of antioxidant activity in the HT-22 cells system. Measurement of intracellular ROS concentration revealed that P15 at the concentration of 1.25 mg/mL significantly (p < 0.05) reduced the intracellular ROS concentration. These results showed that common carp by-product protein hydrolysates are a source of antioxidant peptides with a high potential for food and pharmaceutical industries to develop new nutraceuticals and functional foods.     

In vitro and in vivo hepatoprotective and antioxidant effects of Astragalus polysaccharides against carbon tetrachloride-induced hepatocyte damage in common carp (Cyprinus carpio)

The present study is aiming at evaluating the hepatoprotective and antioxidant effects of Astragalus polysaccharide (APS) on the carbon tetrachloride (CCl₄)-induced hepatocyte and liver injury in common carp in vitro and in vivo. In vitro, APS (200, 400 and 800 μg/ml) was added to the carp primary hepatocytes before (pre-treatment), after (post-treatment) and both before and after (pre- and post-treatment) the incubation of the hepatocytes with CCl₄ at 8 mM in the culture medium. APS at concentrations of 200, 400 and 800 μg/ml significantly improved cell viability and inhibited the elevation of glutamate pyruvate transaminase (GPT), glutamate oxalate transaminase (GOT), lactate dehydrogenase (LDH) and malondialdehyde (MDA) and significantly increased the reduced level of superoxide dismutase (SOD). In vivo administration of APS at the doses of 1.5 and 3 g/kg in the diet for 60 days prior to CCl₄ intoxication significantly reduced the elevated activities of GPT, GOT and LDH and increased the reduced levels of total protein and albumin in the serum; meanwhile, the reduced levels of SOD, glutathione and total antioxidant capacity (T-AOC) were markedly increased and the MDA formation was significantly inhibited in liver tissue. Overall results proved the hepatoprotective action of APS, which is likely related to its antioxidant activity. The results support the use of APS as a hepatoprotective and antioxidant agent in fish.