长江中游宜昌至嘉鱼江段鳊食性研究

研究鳊(Parabramispekinensis)的摄食特征,为长江中游鳊资源的保护提供基础数据支撑。2016年9月至2017年8月在长江中游宜昌、荆州和嘉鱼江段使用三层流刺网进行了季度采样,对鳊肠含物的种类组成及时空差异进行分析。共采集鳊样本213尾,体长14.5～38.0 cm、体重67.0～978.1 g,其中肠道有食物的样本182尾。结果显示:在宜昌、荆州和嘉鱼江段,鳊全年摄食,且摄食强度存在明显季节变化。鳊充塞度以夏季最高、冬季最低;其中夏季肠道充塞度最高为5级,2、3级占52.42%;冬季最高为3级,0、1级占58.82%;春季和秋季最高充塞度均为4级,分别以1级、2级为主;鳊夏季摄食率最高(92.23%),略高于秋季(88.37%),明显高于春季(78.79%)和冬季(67.65%)。饵料生物主要为水生植物和浮游植物,其中浮游植物以颗粒直链藻(Melosira granulata)、变异直链藻(Melosira varians)和粗壮双菱藻(Surirella robusta)为优势种群。饵料生物种类组成在不同江段无明显差异,但呈现明显的季节变化,冬季以浮游植物出现率最高(100.00%),其他季节均以水生植物碎片出现率最高。建议在航道整治等涉水工程建设时,注重保护水生维管束植物及浮游植物,以保护鳊等草食性鱼类的饵料生物来源。     

Influence of Washing and Cold Storage on Lipid and Protein Oxidation in Catfish (Clarias lazera) Surimi

ABSTRACT

Lipid and protein oxidation in catfish (Clarias lazera) surimi during processing and storage were assessed. Catfish surimi were washed in deionized water: M0 (no washing step), M1 (one washing step), and M2 (two washing steps). Lipid, protein, water, and iron contents were determined. M0, M1, and M2 were stored for 0, 1, 4, 7, or 10 days at 4 ± 1°C; at each time point, samples were removed for analyses. Lipid oxidation was assessed by measuring malondialdehyde content. Protein oxidation was assessed by measuring protein solubility and protein sulfhydryl and carbonyl group contents. Based on the results, lipid content, L* and a* (color parameters), and fatty acid content in M1 and M2 were significantly reduced. Lipid oxidation development was faster in M1, and the ranking was as follows: M1 > M2 > M0, with M0 being significantly less oxidized than M1. Increasing the number of washes increased protein oxidation, and the ranking was follows: M2 > M1 > M0. Altogether, lipid and protein oxidation and physicochemical changes occurred simultaneously to different degrees in surimi during various processing and storage conditions.     

Preparation of Chitosan/Rosemary Extract Nanoparticles and their Application for Inhibiting Lipid Oxidation in Grass Carp (Ctenopharyngodon idellus) during Cold Storage

This study investigated a preparation of chitosan/rosemary extract nanoparticles (CS/RE-NPs) based on the principle of ionic gelation and their application for inhibiting grass carp lipid oxidation. CS/RE-NPs were found to have a rosemary extract (RE) encapsulation efficacy of 40.33%, average particle size of 199.90 nm, and zeta-potential of 35.60 mV. Structural analysis using UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM) indicated that the RE s were well incorporated into the CS-NPs. Treatment of the CS/RE-NPs inhibited lipid oxidation of the grass carp during cold storage, and the peroxide value (PV), thiobarbituric acid-reactive substance (TBARS) value, and lipoxygenase (LOX) activity of the CS/RE-NP-treated samples were lower than those of RE and CS-NP-treated samples, respectively. CS/RE-NP-treated samples also slowed the growth of bacteria, enhanced the organoleptic quality, and prolonged the shelf life of grass carp. This study suggested that CS/RE-NPs can be used as an antioxidant delivery system to inhibit lipid oxidation and improve food quality.     

The determination of lipase and phospholipase activities in gut contents of turbot (Scophthalmus maximus) by fluorescence-based assays

To study the potential of fluorescence based assays in the study of lipid digestion in fish, acyl esters of 4-methylumbelliferone and 1-acyl-2-[6 (7 nitro-1,3 benzoxadiazol-4-yl)amino]caproyl labeled phosphatidylcholine compounds (NBD-PC) were used as substrates for the assay of neutral lipase and phospholipase, respectively, in the gut contents of turbot. 4-Methylumbelliferyl hepatanoate (4-MUH) was hydrolysed at a higher rate than the butyrate or oleate esters whilst the hexanoic (C6) ester of NBD-PC was a more convenient substrate for the phospholipase assay than the dodecanoic (C12) ester. Neutral lipase activity was almost 10% higher when 50 mm potassium phosphate buffer pH 7.8 was used instead of 0.01 m citrate/sodium phosphate buffer pH 7.2. Both assays were very sensitive: neutral lipase and phospholipase activities were detectable at a minimum protein concentration in the digesta of 0.04 and 1.25 mg/ml, respectively. When the variations in lipolytic activities with gut segment and with size of fish were examined neutral lipase activity was always found to be higher in the hindgut and rectum segments than in the foregut. Although phospholipase activity was also found to be highest in the hindgut of the largest fish examined (av. wt. 182.3g), in fish of average weight 8g fish the activity was similar in all three segments. In the digesta from the whole gut of smaller fish (av. wt. 0.2, 0.6 and 1.43g) neutral lipase and phospholipase activities increased with increasing body mass when expressed as per ml of digesta. It is concluded that fluorescence-based assays are applicable to the study of lipid digestion in fish of different size.     

Lipid Hydrolysis and Oxidation of Mackerel (Scomber scombrus) Mince

Atlantic mackerel was stored at refrigeration or frozen temperatures under vacuum or in air with various treatments to determine lipid hydrolysis and oxidation in the fish muscle. Lipid oxidation in the fish minces occurred continually as long as the samples were exposed to air independent of hydrolytic activity which was deactivated or retarded by cooking the sample or by lowering the storage temperature (-40°C). Lipid oxidation was observed not only in the free fatty acids, but also in the triacylglycerides and the phospholipids extracted from mackerel mince.     

Decrease of Lipid Oxidation for Dried Shrimp (Acetes chinensis) Preservation Using Alkaline Lipase Hydrolysis Technology

ABSTRACT

In this study, the degreasing technology using alkaline lipase hydrolysis for Chinese dried shrimp (Acetes chinensis) was investigated, with the purpose of decreasing lipid oxidation during dried shrimp preservation. The salt, moisture, and lipid contents of the shrimp were 6.01, 32.51, and 2.95%, respectively. The optimum enzymatic hydrolysis condition for effective decrease of shrimp lipid was obtained: lipase concentration 40 U/mL, pH 10, soaking time 60 min, soaking temperature 30°C, and shrimp/liquid ratio 1:20 (w:v). Under this optimum condition, the residual lipid of the shrimp was reduced to 2.28%, and the degreasing rate reached 49%. During 30-day preservation, the thiobarbituric acid-reactive substances (TBARS) value (0.185 mg/kg of dried shrimp and 0.131 mg/kg of degreased dried shrimp at Day 30) of degreased shrimp was lower than the shrimp without degreasing, indicating alkaline lipase hydrolysis could effectively prevent lipid oxidation and inhibit oxidative rancidity during dried shrimp preservation.     

Lipid digestion in turbot (Scopthalmus maximus) 11: Lipolysis in vitro of 14C-labelled triacylglycerol,cholesterol ester and phosphatidylcholine by digesta from different segments of the digestive tract

Preparations of digesta from the stomach, foregut, hindgut and rectum of turbot (Scophthalmus maximus) were assayed for the ability to hydrolyse glycerol tri[1-¹⁴C]oleate (¹⁴C-TAG), 1,2-di[1-¹⁴C]palmitoyl L-3-phosphatidylcholine (¹⁴C-PC) and cholesterol [1-¹⁴]oleate (¹⁴C-CE) over 1,2,3 and 17h. In the assay of foregut digesta with ¹⁴C-TAG substrate, 37.8% of the total radioactivity was found in the FFA class after the first hour of incubation. This value increased to a maximum of 68.5% of the available label after 17h incubation. Over the same time the proportion of radioactivity in diacylglycerols (DAG, 31.6%–7.4%) decreased while that in the monoacylglycerols increased (MAG, 14.0%–22.3%). In assays of digesta from the hindgut and rectum, after 1 h of incubation, the proportion of radioactivity recovered in FFA represented 64.9% and 74.8%, respectively, whereas the proportions in both DAG and MAG decreased with incubation time. Similarly to ¹⁴C-TAG, the highest rate of lipolytic hydrolysis of ¹⁴C-CE occurred in digesta from the posterior digestive tract where the proportions of radioactivity recovered in FFA of the hindgut (50.0%) and rectum (81.9%) preparations were substantially higher than those of the stomach (3.5%) and the foregut (14.4%) after 1h. With ¹⁴C-PC as substrate the levels of radiolabelled FFA in both the foregut and the hindgut (2.4% and 7.6%, respectively) were markedly lower than the 37.5% in the rectum. The results suggest that the posterior digestive tract is very active in non-specific and phospholipid lipolysis and a region where the major part of lipid digestion takes place.     

Effects of Delayed Processing of Pink Salmon (Oncorhynchus gorbuscha) By-products on Fishmeal Quality

The effects of storage temperature and time on raw pink salmon by-products were evaluated in relation to the fishmeal produced. Chemical analyses were performed on the raw and processed by‐products at two temperatures. Total volatile base nitrogen values indicated substantial spoilage by day 2 at 15.4 ± 1.4°C and day 6 at 6.0 ± 0.8°C. For most biogenic amines in raw by-products stored at 15.4°C, there were many significant differences from the fresh by-products by day 2. For by-products stored at 6.0°C, significant changes in biogenic amine were evident by day 2 and continued to increase. The thiobarbituric acid reactive substances (TBARS) values of the raw material stored at 15.4°C started showing significant changes from fresh on day 3 and at 6.0°C on day 4. The lipid oxidation (TBARS) was significantly different from fresh by day 2. Biogenic amines in fishmeals suggested some changes occurred between day 0 and day 3 at 15.4°C and by day 7 at 6.0°C.     

Effects on Lipid Oxidation and Bioactive Properties of Rainbow Trout Fillets Fed with Barley

Barley concentrations ranging from 0% to 32% were incorporated into rainbow trout (Oncorhynchus mykiss) diets. The effect of barley concentration on lipid peroxidation and antioxidant activity of fish fillets were analyzed. Results showed that the inclusion of barley in rainbow trout diets had an inhibitory effect on lipid oxidation, probably associated with certain bioactive compounds in barley that could interact with scavenging and reducing metabolites involved in lipid oxidation. Concentrations up to 8% of barley produced fish fillets with high antioxidant activity and higher levels of alpha-tocopherol.     

Stability of Fish Powder Made from Saithe (Pollachius virens) as Measured by Lipid Oxidation and Functional Properties

ABSTRACT

Lipid oxidation and functional properties were monitored in spray dried fish powder made from saithe (Pollachius virens) by-products. The fresh powder exhibited slight antioxidant activity in a model system of linoleic acid emulsion. The freshly made powder had low lipid extract-ability in polar solvents and over 30% free fatty acids (FFA). Further lipid oxidation took place during storage, independent of storage temperatures. Functional properties measured by color changes, water-binding capacity, apparent viscosity and protein solubilty changed more during storage at 30°C than 0°C.     

Fishmeal quality and ethoxyquin effects on the weaning performance of ballan wrasse (Labrus bergylta) larvae

Fishmeal diets are shown to be unfavourable for successful weaning of ballan wrasse (Labrus bergylta) larvae. Variable fishmeal quality, and/or a possible negative effect of ethoxyquin (EQ) and/or palatability could be the reason for the reduced growth and increased mortality observed. This study weaned wrasse larvae on either a control diet of freeze–dried shrimp and cod fillet, or fishmeal‐based diets with 0, 11 or 44 ppm EQ, for 1 month. Lower final body weight and higher mortality were related to increased inclusion of EQ. Furthermore, fishmeal diets had increased lipid oxidation values with decreased EQ content, whereas the control diet had the lowest lipid oxidation levels. A combined negative effect of oxidation and EQ supplementation could have lowered the palatability of the feeds and be the reason for the unsuccessful larval weaning. Use of EQ is inevitable in large‐scale production of feed ingredients; however, the use of high‐quality ingredients with low EQ inclusion, or its replacement with other antioxidants, may be necessary for successful intensive culture of some marine fishes.     

Evaluation of Turmeric Extract as an Antioxidant for Frozen Streaked Prochilod (Prochilodus lineatus) Fillets

This study aimed to investigate the efficiency of turmeric (Curcuma longa L.) extract, applied as a marinade or glaze, as an antioxidant for frozen streaked prochilod (Prochilodus lineatus) fillets. The turmeric extract contained 5.5 ± 0.1 mg curcumin/mL, and the experiment was performed using a diluted extract with 100 µg curcumin/mL. Analysis of the antioxidant activity with 2,2-diphenyl-picrylhydrazyl (DPPH) and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals confirmed the high antioxidant activity of curcumin. However, under the experimental conditions, curcumin extract presented no effectiveness for inhibiting lipid oxidation in frozen streaked prochilod fillets, as the concentration of thiobarbituric acid reactive substances did not differ (p > 0.05) between treated and control fillets. Sensory evaluation of the fillet appearance indicated that the change toward a more yellow color in treated fillets negatively affected its acceptance. However, the acceptability of the odor of raw and cooked fillets was similar for treated and control samples. These results may be explained by the fact that good in vitro performance of antioxidants is not always replicated in foodstuffs owing to the complexity of food matrices. Additionally, the low lipid content of the fish and the low amount of curcumin applied to the fillets may have contributed to the inefficiency of turmeric extract.     

Effect of Zataria multiflora Boiss (Avishan Shirazi) Essential Oil on Oxidative Progress in Frozen Cobia Fish Fillets During Storage

Antioxidants have been widely used as additives to provide protection against oxidative degradation of foods by free radicals. The effect of thyme essence (Zataria multiflora Boiss) on the rancidity development in cobia (Rachycentron canadum) fillets during frozen storage was studied. Cobia fillets were treated with thyme essence (250 and 500 ppm) and then stored at??18°C for up to 6 months. Rancidity development was measured by several biochemical indices including free fatty acids (FFA), peroxide value (PV), thiobarbituric acid (TBA), and complemented by sensory analysis (flesh odor, consistency, and appearance). Also, pH and expressible moisture were measured during 6-month storage. Proximate composition was also determined in the first day. TBA, PV, and FFA levels increased in all treatments due to lipid oxidation. Thyme essence showed an antioxidative effect in cobia fillets during frozen storage as indicated by TBA, PV, and FFA levels. Results showed that FFA, primary and secondary oxidation products, expressible moisture (EM), and pH of thyme essence treated samples were significantly lower than those of the control samples (p < 0.05). Thyme essence retarded oxidative changes in frozen cobia fillets, and the best oxidation inhibition was obtained using thyme essence at 500 ppm.     

Oxidative Stability of Dried Seafood Products during Processing and Storage: A Review

Drying is a traditional and important seafood processing technology. Lipid oxidation is one concern during the processing and storage of dried seafood products. Various factors including pretreatment, drying method, and storage conditions can have an impact on the oxidative stability of dried seafood products. Influence of these factors on the oxidative stability of dried seafood products as well as the possible mechanisms are reviewed. This review could serve as a reference for the production and research of dried seafood products.     

Control of Lipid Oxidation and Texture Changes in Frozen Sardine Mince by Combined Use of Milk Protein Concentrate and Caffeic Acid

The effectiveness of milk protein concentrate (MPC) and caffeic acid in controlling lipid oxidation and texture changes in 6-month frozen stored sardine mince was investigated using two different concentrations of caffeic acid (200 and 400 ppm) with and without MPC (4%). The extent of lipid oxidation was monitored by measuring thiobarbituric acid reactive substances (TBARS) while changes in the texture of mince due to frozen storage were assessed using Texture Analyzer (TA.XT Plus) and sensory analysis. Cooking loss upon frozen storage was also determined. The addition of MPC and/or caffeic acid significantly reduced lipid oxidation throughout the storage period. However, neither added benefit nor synergistic effect in retarding lipid oxidation was shown by caffeic acid. MPC not only retarded lipid oxidation but also moderated texture hardening, cooking loss, and moistness during frozen storage. No improvement by caffeic acid alone and no significant differences in sensory firmness and moistness between MPC-added mince with and without caffeic acid indicate that caffeic acid did not play any role in texture and moisture control. This study suggests that lipid oxidation and texture of frozen sardine mince can be better controlled by using MPC alone.     

Oxidation of glutathione during hydroperoxide metabolism in isolated hepatocytes of rainbow trout (Salmo gairdneri)

Freshly isolated rainbow trout hepatocytes were exposed to tert-butyl hydroperoxide (BuOOH), a substrate for glutathione peroxidase. BuOOH at a concentration approximately equimolar (1 mM) with intracellular reduced glutathione (GSH) caused a reversible increase in intracellular glutathione disulphide (GSSG) but did not compromise cell viability or damage membrane lipids. BuOOH at 10 mM caused a large irreversible increase in intracellular GSSG followed by efflux into the medium. Considerable leakage of lactate dehydrogenase and loss of highly unsaturated fatty acids, particularly docosahexaenoic acid also occurred. Dependence of hydroperoxide removal on flux through the hexose monophosphate pathway was suggested by the increased release of ¹⁴CO₂ from [1-¹⁴C] glucose from hepatocytes incubated with BuOOH.     

Evaluation of Egg White Protein-Based Coatings to Improve the Protection of Frozen Atlantic Salmon (Salmo salar)

ABSTRACT

The effects of different egg white protein coatings on Atlantic salmon quality preservation after 4 months of frozen storage were evaluated. These coatings increased the yield of the fillets and protected them from lipid oxidation, providing better protection than glazing. Egg white protein coatings were better options than glazing to preserve salmon color during frozen storage. The best results were obtained with the application of coatings before freezing. No clear effects of the type and concentration of plasticizer in most quality parameters were found. Egg white protein + glycerol 2:1 applied before freezing was the best coating for frozen Atlantic salmon protection.     

Fatty Acid Profiles and Lipid Oxidation Status of Sun Dried,Deep Fried,and Smoked Sardine (Rastrineobola argentea) from Lake Victoria,Tanzania

Freshwater fishes contain long chain omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) of highest nutritional value. PUFAs in fish are susceptible to oxidative damage during processing and subsequent storage. Sardines (Rastrineobola argentea) are an important fish species of Lake Victoria, constituting 72.3% of the total landings by weight on the Tanzanian side of the lake. Fatty acid profiles and lipid oxidation status of sun-dried, deep-fried, and smoked sardines were investigated. Lipid oxidation was assessed by peroxide value, thiobarbituric acid reactive substances (TBARS), and free fatty acids. Fatty acids were analyzed by gas chromatography with flame ionization detector. The three omega-3 PUFAs: docosahexaenoic acid (C22:6n-3), docosapentaenoic acid (C22:5n-3), and eicosapentaenoic acid (C20: 5n-3) contributed 57–60, 63, and 38% of PUFAs in sun-dried, smoked, and deep-fried sardines, respectively. Lipid oxidation reactions were more pronounced in sardines dried on sand and rocks, with TBARS values 97.87 and 84.18 µmolMDA/kg, respectively. The polyene index was significantly lower (p < 0.05) in deep-fried sardines, indicating lower retention of PUFAs in the product. Lake Victoria sardines are a rich source of omega-3 PUFAs. PUFAs in sun-dried sardines are prone to oxidative damage. Smoking resulted in relatively higher retention of omega-3 fatty acids in products.     

Effects of dietary oxidized fish oil on growth performance and skin colour of Chinese longsnout catfish (Leiocassis longirostris Günther)

A 61‐day experiment was carried out to investigate the effect of dietary oxidized fish oil on growth performance and skin colour of Chinese longsnout catfish (Leiocassis longirostris Günther). Seven diets (Diet 1–7) containing different levels of oxidized fish oil (0, 10, 20, 30, 40, 50 and 60 g kg^?1 dry diet) were evaluated at same dietary lipid level (60 g kg^?1 diet). Fish skin colour (CIE L*a*b*) and melanin content was measured at three zones of fish body: back (Zone I), belly (Zone II) and tail (Zone III). The results showed that there were no significant differences in growth or feed utilization. Apparent digestibility coefficient of energy (ADCe) decreased while those of dry matter (ADCd), protein (ADCp) or lipid (ADCl) were not affected. Lightness (L*) of Zone I or II were not influenced while L* of Zone III decreased. Oxidized oil increased melanin content of Zone III. No apparent effects on the thiobarbituric acid reactive substances (TBARS) values of blood serum, liver and muscle were observed. In conclusion, dietary oil oxidation did not affect fish growth performance. Fish tail skin lightness was lower in the fish fed with high dietary oxidized fish oil and was positively correlated to melanin content.