جستجوی مقالات مرتبط با کلیدواژه « خصوصیات فیزیکوشیمیایی » در نشریات گروه « شیلات »

The lakes behind the dam considered as semi-natural resources and have a special role in aquaculture. In order to achieve management goals, it is necessary to know the pattern of changes in biotic and abiotic parameters in the lake behind the dam. For this purpose, in order to determine water quality using water quality indicators (WQI) 12 physicochemical properties (water temperature, dissolved oxygen, salinity, acidity, electrical conductivity, suspended solids, total hardness, total alkalinity, nitrate, ammonia, phosphate and phosphorus Total) was evaluated in 2018 on a monthly basis for one year at 7 stations of Golestan dam in Gonbad city. Although temporal and spatial changes observed in some measured factors; According to the WQI index in Golestan Dam, it was relatively average to good in different months. Therefore, it evaluated as favorable for the breeding of tropical and subtropical fish.

This study was carried out to investigate the different cooking methods on some physicochemical properties and fatty acids composition of narrow-clawed crayfish (Astacus leptodactylus). In this study, four cooking methods including grilling, boiling, frying, and cooking in microwave with three repetitions were performed for 84 pieces of crayfish caught from Aras Dam. The results of the study of physicochemical properties showed that the maximum and minimum amounts of protein content were obtained in steamed (17.70±0.39 %) and deep-fried (15.13±0.14 %) groups, respectively. The highest level of fat was recorded in the deep-fried method (7.36±0.25 %) and there was no significant difference among the other treatments (P>0.05). The highest amount of pH was observed in steamed treatment. According to the results of cooking loss, the highest value was observed in the microwaved method, while the deep-fried and grilled treatments had the least value. Also, the results of texture profile analysis showed that the highest hardness 1 and 2 were observed in deep-fried treatment (P<0.05). Fatty acids composition results showed that the highest values of eicosapentaenoic acid (20.25±0.13 %) and docosahexaenoic acid (6.31±0.26 %) were recorded in the steamed method and the lowest values was observed in deep-fried treatment (P<0.05). Therefore, it can be concluded that the steamed cooking method had less negative impact on the nutritional value and physicochemical properties and the reduction of unsaturated fatty acids of freshwater narrow-clawed crayfish tail meat than other cooking methods.

The present study was carried out to investigate the physicochemical changes of farm-raised Beluga minced meat during the storage period in the refrigerator under the influence of hydroalcoholic extract of Ulva intestinalis macroalgae as a natural preservative. The minced fish was prepared with concentrations of 0 (control), 12.5, 25 and 37.5 mg/kg of the macroalgae extract. A sample with synthetic antioxidant (BHT) was included. Physicochemical properties (peroxide, volatile nitrogen, free fatty acids, thiobarbituric acid and color) of the samples were measured on 0, 4, 8 and 12 days. On the fourth day of the storage, the lowest values of peroxide index (5.1 meq/kg oil), thiobarbituric acid (0.23 mg malondialdehyd/ kg of meat), volatile nitrogen (25.55 mg N/100 g) and free fatty acids (0.47% oleic acid) was measured in treated samples with 36.5 mg of macroalgae extract compared to control and BHT treatments (P<0.05). The results of color indicated that the red and yellow indexes were increased during the storage period, while the highest amount of them were observed in treated samples with the macroalgae extract compared to control and BHT samples. Therefore, this algal extract might be considered a natural preservative and the best antioxidant effects was obtained in 37.5 mg of the extract per kilogram of the minced meat, which can be prolonged Beluga minced meat up to 12 days.

To improve shrimp quality, it is of importance to evaluate shrimp spoilage characteristics. Therefore, physicochemical, microbiological and sensory changes of white shrimp (Metapenaeus affinis) during storage at ice (0ºC) and refrigerator (4±1ºC) were assessed. Mesophilic, psychrophilic, Entrobacteriaceae, Staphylococcus sp., H2S producing bacteria (white colony) and H2S producing bacteria (black colony) counts of stored in ice at day 16 were 7.50, 7.83, 7.13, 6.42, 7.06 and 6.45 log10 CFU/g, respectively. Mesophilic, psychrophilic, Entrobacteriaceae, Staphylococcus sp., H2S producing bacteria (white colony) and H2S producing bacteria (black colony) counts of stored at refrigerator at day 16 were 8.76, 9.80, 8.13, 6.95, 8.28 and 7.20 log10 CFU/g, respectively. Mesophilic, psychrophilic, Entrobacteriaceae, Staphylococcus and H2S producing counts were higher in white shrimp stored at refrigerator compared to white shrimp that stored at ice. Thiobarbituric acid, free fatty acid, total volatile bases nitrogen and pH indexes were higher in white shrimp stored at refrigerator compared to white shrimp stored at ice (p<0.05). The lowered rate of increase in pH, total volatile basis nitrogen (TVBN) were obtained in shrimp stored at ice. H2S-producing bacteria were the dominant group of microorganisms at refrigerator whereas Enterobacteriaceae were dominant at ice. Total volatile basic nitrogen correlated well (r= 0.859) with the sensory scores in shrimps stored at ice and correlated well (r= 0.987) with the sensory scores in shrimps stored at refrigerator. Correlation coefficient of bacteria count and sensory evaluation in shrimp stored at ice and refrigerator was above 0.824. The results showed that using of ice could improve the microbiological count and delay the spoilage and extend the shelf life of white shrimp (M. affinis).

Dam reservoirs have important rules in aquaculture and fish farming in many countries. In this regard, water samples of Azad Dam reservoir (Sanandaj) were collected at five stations from July 2015 to June 2016. Then, the results of 18 physico-chemical parameters were compared with the aquaculture standards and thresholds. Results showed that thermocline and oxycline was started from June and they vanished in December. Maximum level of thermal and oxygen stratified were registered during August and June, respectively. Mean of the most physico-chemical parameters were significantly different between surface and bottom layers (T-Test, p