نشریه علوم و فنون شیلات
سال ششم شماره 2 (پیاپی 19، تابستان 1396)

The extraction of hydrocolloids from seaweeds is associated with production of secondary metabolites during pretreatment step. In this study, the antioxidant properties were evaluated for secondary metabolites from brown seaweed S. angustifolium. The crude extract obtained by 80% ethanol for four hours and then partitioned using hexane, chloroform, ethyl acetate and water. The extraction yield was found to be 4% for crude extract and varied between 2.8-43% for fractions. The evaluation of antioxidant properties revealed a successful solvent fractionation in portioning antioxidant compounds. Among various fractions, ethyl acetate exhibited the highest activity in DPPH radical scavenging (75.78%), ABTS radical scavenging (88.92%), reducing power (67.54%) and total antioxidant (0.34 Abs) capacities. The highest amount of phenolic contents was found in ethyl acetate fraction (277.86 mg/ TA in extract) while the lowest amount was in aqueous fraction (21.36 mg/ TA in extract). The highest correlation (R2 = 0.88) was observed between total phenolic content and total antioxidant activity. Overall, the results of current study show that ethanol extract of S. angustifolium contains major bioactive compounds suggesting its potential application in food industry as a natural antioxidant.

Single or combined effects of medicinal plants, garlic (Allium sativum) and ginger (Zingiber officinale) powders on hepatosomatic index, body composition, digestive enzymes and resistance rate in Sobaity sea bream (Sparidentex hasta) fry were investigated for 8 weeks. Biomar diet (54% protein and 18% lipid) supplemented with 0 (control), 1% garlic, 1% ginger and 1% garlic 1% ginger in a totally randomized design trial in triplicate. A total of 240 fingerlings of 3.80 ± 0.31 (g) average weight were randomly distributed in 12 tanks. Results showed that there were significant differences in hepatosomatic index among treatments (p>0.05). Significant difference was observed in body composition (p>0.05), as protein and lipid contents in the whole body increased in fish fed with garlic/ginger and ginger groups. Lipase enzyme activity increased significantly in garlic/ginger and ginger groups compared to control group. The highest amylase enzymes activity was observed in ginger group (p

An experiment was conducted to evaluate the effects of stocking density on growth and survival of Nile tilapia (Oreochromisniloticus) in brackish water earthen pond. Fish with initial weight of 13 g kept in three stocking density 3, 6 and 9 fish/m2 in duplicates and were fed on rainbow trout feed for 105 days during the light period. The results showed significant reduction in final weight, weight gain, daily growth rate, specific growth rate and survival by increasing stocking density, while feed conversion ratio enhanced in higher stocking densities (p

Optimization of protein hydrolysate from head and arms of cuttlefish (Sepia pharaonis) was examined. For this purpose, response surface methodology (RSM) was employed to investigate the effects of different operating conditions on hydrolysis process of cuttlefish protein by the application of alcalase enzyme. A Box-Behnken design with three factors at three levels was used for hydrolysis optimization and to check any individual or interaction effects between the experimental factors. In this method, the effects of three independent variables, including temperature, pH and enzyme to substrate ratio, were investigated on hydrolysis rate as a surface response. The mathematical model showed a good fitness with experimental data. Optimum conditions for temperature, pH and enzyme quantity were determined as 54.33 ˚C, 8.49 and 1.97 %, respectively, which caused nearly 14.5 % hydrolysis degree. Based on the lack of fitness factor which was not significant, it was deduced that the resulted model was capable of prediction at different studied levels of variables. In this study, in order to confirm the conditions that proposed by mathematical equation, the hydrolyzed protein was produced accordingly at which resulted in a 16.8% hydrolysis degree. This finding was according to the aim of present trial by producing a protein hydrolysate with maximum hydrolysis degree. Then the functional properties of protein hydrolysate powder from optimized conditions were measured. Functional properties of this protein powders indicated a good solubility, but weak levels of emulsifying and foaming capacities.

For quality assessment of coated fish fillet with sodium alginate containing inulin, fish fillet were coated with sodium alginate containing 10, 20, 30 and 40 percent inulin using two methods, including dipping and vacuum impregnation. Then fructan were determinate in coated samples. The samples including 20 and 40% inulin in vacuum impregnation and dipping respectively were selected for further study based on their higher fructan content. Therefore, the chemical and microbial changes of selected samples were investigated during 16 days, with 4 days interval in refrigerated condition (40C). Results showed that the fructan content had not changed significantly (p≥0/05) during the storage period. Peroxide in the middle of storage period was increased and then decreased significantly (p≥0/05) by the end of storage time. Quality indexes such as pH, thiobarbitoric acid (TBA), total volatile basic nitrogen (TVB-N), total plate count bacteria, psychotropic bacteria and peroxide increased significantly (p≥0/05) along time. In all of the samples, TBA at the end of 12 day storage, TVB-N at the end of 16 day storage, anaerobic bacteria count and pseudomonas bacteria count at the end of 12 day storage were more than acceptable limit of fresh fish. In the conclusion, fructan of coated fish fillet had not changed significantly during refrigerated storage, as well as shelf life of coated fish fillet by dipping and vacuum impregnation in refrigerated condition storage (40C) was less than 12 days.

Growth indices (WG and SGR), food (FCR) and protein efficiency (PER and PCE) of fingerling Nile tilapia, Oreochromis niloticus,were evaluated in 3 synchronous examinations with 12 treatments in triplicates. Groups of control, canola meal (at rates of 25, 50, 75 and 100%), cottonseed meal (at rates of 15, 25, 35 and 45%), as the replacements of expensive protein sources (fish meal and soybean meal), and azolla (at rates of 13, 21 and 29% of diet) were studied. Growth indices, total food intake and protein intake of the control were the highest of all. They decreased with increase in plant protein in every group (p0.05) between control and canola meal (at rates of 25 and 50%), cottonseed meal (at rates of 15, 25 and 35%) and azolla (at rates of 13 and 21%). Total food intake, protein consumption and growth indices decreased, because all plant protein ingredients were unpalatable. If the problem of palatability is solved, it seems that the expensive protein sources replace with canola meal and cottonseed meal at the rates of 50 and 35% respectively, and azolla can be used at the rate of 21% in diets.

The effect of dietary composition and starvation on growth and plasma metabolites in rainbow trout of 14 g average initial weight was investigated. A group of 240 trout juveniles were distributed in 12 of 150 L tanks. The experiment was performed in a 2*2 factorial design with 2 lipid levels (10 and 18%) and 2 feeding conditions (feeding and starvation) with 4 treatments each with 3 replicates. The fish were fed on diet 1 (lipid 10%, carbohydrate 29%) and diet 2 (lipid 18%, carbohydrate 19%) with the same protein level (47%) and energy. The juveniles were fed to apparent satiation for 3 weeks, followed by starving for 2 weeks and then refed for 3 weeks. The biometery and plasma biochemical parameters were analysed in the day of 21 (end of 3 weeks feeding), 35 (after 2 weeks starvation) and 60 (end of 3 weeks refeeding). Based on the result, the best growth performance in the fish occurred in diet with 10% lipid in control group (feeding group) and no compensatory growth occurred in this treatmennt after 2 weeks starvation. Moreover, the result of body composition showed the starvation and diet composition had more effect on body lipid than body protein and body lipid content decreased by starvation. The starvation and diet composition did not have any significant effect on cholesterol and triglyceride, but they induced decreasing plasma glucose level in the trout.

The effect of different extraction methods (soxtec apparatus, ultrasound, solvent and wet rendering) on yield, quality and fatty acids composition of oil extracted from the offal of common carp (Cyprinus carpio) was compared. For determination of the oil quality, PV, TBA, FFA, conjugated diene, non-enzymatic browning indexes and fatty acids composition were measured. Results showed that soxtec apparatus had the highest efficiency compared to other extraction methods. In addition, ultrasound extraction had higher yield in comparison to solvent methods. Moreover, the wet rendering method had lower oil yield. The quality indexes of oil extracted with ultrasound had significantly lower quality compared to other extraction methods. Hence, the oil extracted with wet rendering methods had better quality. Oil extracted with all of the methods contained high amounts of MUFA, also oil extracted by ultrasound method had the highest content of DHA and EPA as compared with other extraction methods.

The effect of different lipid extraction methods (including, Bligh & Dyer, Smeds, Bligh & Dyer using Dichloromethane, Folch, Roese Gottible, Soxhlet used petroleum ether – dry and wet- and Soxhlet used N-hexane) on total fat and fatty acid composition in rainbow trout (Oncorhynchus mykiss) was investigated. According to the results, the Bligh & Dyer method showed a higher fat extraction efficiency than Soxhlet (wet), Smeds and Roese Gottible, while no significant difference was observed with the other methods. No significant differences were found in total SFA, total MUFA, and total PUFA of different extraction methods. The omega-3/omega-6 ratio ranged between 0.20-0.29. The highest amount of polyene index (PI) was 0.34, but no significant differences were found between different extraction methods. Taking fat quality and quantity, finance, toxicity, and theease of operation, the most efficient method for rainbow trout lipid extraction was the “optimized Bligh & Dyer using Dichloromethane”.

The growth performance, biomass and survival of the marine polychaete (Perinereis nuntia)reared on different sandy substrates were evaluated. For this purpose, larvae of P. nuntia with initial length of 1 cm were collected and cultured on 4 different sandy substrates for 4-month period. The tested sands were collected from Bandargah Beach (Bushehr provience) and graded by screenings to 4 substrates grain size of 4 mm with 4 replications. At the end of the experiment, the worms grown in the sandy bed of less than 0.5 mm had significantly higher final weight and specific growth rate (p