جستجوی مقالات مرتبط با کلیدواژه "ph" در نشریات گروه "شیلات"

Coenzyme Q10, as an antioxidant compound, has a role in the electron transport chain of the animal cell. To study the effects of this natural antioxidant on the quality and composition of the fish carcass; rainbow trout were fed by five dietary treatments containing 0, 25, 50, 100, and 200 mg/Kg of coenzyme Q10 during an 8-week feeding trial. The results showed that coenzyme Q10 increased the pH and decreased the peroxide value of carcass fish on the first day of keeping in the refrigerator. The carcass thiobarbituric acid index was not affected by coenzyme Q10 at different refrigerator storage times (P< 0.05). Dietary levels of coenzyme Q10 significantly improved the organoleptic properties of fish flesh. Feeding the fish with various diet levels of coenzyme Q10 elevated the total omega-3, eicosapentaenoic acid, docosahexaenoic acid, and long-chain polyunsaturated fatty acids in the carcass compared to the control group. Overall, the results of this study showed that using coenzyme Q10 in the levels of 100-200 mg/kg of diet improve rainbow trout carcass quality.

One of the important factors in the use of natural pigments in various foods is their stability and preservation of their antioxidant properties under the production and storage conditions. Astaxanthin is one of these natural pigments that microalgae are one of its resources. In the present study, after the extraction of astaxanthin from hematococcus microalgae (Haematococcus pluvialis) by a combined method (HCL-Acetone), the effect of temperature, pH, and time parameters on its stability and antioxidant activity (DPPH free radical scavenging activity and reducing power of ferric) were evaluated. The results showed that the effect of temperature, pH and time factors alone and the interactions between the time and temperature were significant (p<0.05). However, the interactions of pH with time, pH with temperature, and the interaction of three factors together on the concentration and stability of astaxanthin were not significant (p>0.05). According to the findings, the antioxidant activity and pigment stability at 4 °C was more than 20 °C and with increasing the storage time, these properties were decreased. The pH changes did not have much effect on the pigment properties, although the results at pH=5.5 were relatively better than pH=4.5. Among the studied treatments, DPPH free radical scavenging activity as well as the reducing power of the extracted pigment ranged from 45.5-93.11% and absorption of 0.31-0.81 at 700 nm, respectively. This property makes it possible to use this pigment in food products as an antioxidant. However, use of various methods such as coating the pigment for using in heat-treated foods is recommended due to the low stability of the pigment at the higher temperatures.

The aim of this study was to investigate the effect of a natural additive called chitosan on changes of approximate composition indices (moisture, fat and protein) and pH in defrosted fish fillet (Huso huso). The study consisted of 2 treatments: chitosan-free treatment (control treatment) and 1% acid soluble chitosan treatment. Both treatments were stored at -18 ° C for 4 months. Fillets were freezed and examined on day 0 (10 hour after freezer storage) and the second and fourth months. In terms of approximate composition, the use of acid-soluble chitosan significantly caused delaying the reduction the moisture, fat, and protein content of fish fillets compared to chitosan-free fillets during freezer storage. In addition, 1% acid-soluble chitosan caused keep it low the pH of fish fillet during freezer storage compared to the control group.

The aim of this study was to investigate the effects of temperature, pH and orange essential oil on reducing the growth rate of L. monocytogenes. The variables included 45 ° C (for 144 hours), 50 ° C (for 72 hours), 55 ° C (for 6 hours), 4 pH levels (4, 5, 6) and essential oil citrus (Citrus aurantium L.) in 0.2, 0.4 and 0.6% levels on the growth rate of L. monocytogenes in cold smoked silver carp fillet. The results showed that the number of bacteria increased with increasing pH at the studied temperatures (P<0.05), But correlation analysis showed no correlation between L. monocytogenes and pH. The increase in temperature significantly reduced the number of bacteria in cold and hot smoked silver carp fillets, so that the lowest bacterial count in both cold and hot smoked fillets was counted in a temperature of 55 ° C. The correlation between number of bacteria and temperature also confirmed this. Regarding the effect of citrus essential oil on the number of bacteria, the results showed that in the conditions of pH and constant temperature, increasing the percentage of essential oil, the number of L. monocytogenes decreased and this decrease, especially in the treatment of 0.6% of orange essential oil. Also, at the same temperature and pH, hot smoking compared to cold smoking was more effective in reducing the number of L. monocytogenes. Given that the number of bacteria counted in both methods of smoke at different temperatures and pH was not higher than the107 Log cfu/ g standard, it could be argued that smoke is a reliable way to increase the shelf-life of silver carp fillet and the best temperature and time to smoke was 55 ° C for 6 hours, at pH = 4, and essential oil level was 0.6%.

This study was conducted to investigate the effect of activating solutions containing different concentrations of calcium, magnesium and pH change in the Billard standard fertilization solution on sperm motility of brown trout. Sperm catching from the male fish was done after anesthetizing. Sperm samples were then mixed together and density (87.0±30.10 million per milliliter) and spermatocrit (23.0±0.58%) of the pooled sample were calculated. Experimental activating solutions were prepared by addition of bivalent ions of calcium and magnesium with a concentration of 1, 2, and 3 mmol L-1 in the Billard solutions. Three other experimental groups were prepared by making changes in the PH of Billrd solution (8, 8.3, and 9). Then, Sperm motility in each experimental solutions and standard solution Billard (control) were compared. The highest Sperm motility of brown trout was found in the solution containing 1 mM calcium ion with the 64.7±8.6 s, which did not show significant difference with the solution containing pH 8 (p>0.01).The minimum duration of sperm motility was also recorded in pH 9.5 fertilization solution with the time of 24.3±2.6 s compared to the other treatments (p0.01). Among bivalent ions the most motility of brown trout sperm was observed in the solution containing 1mM calcium. Therefore, the type and concentration of bivalent ions followed by the pH in activating solutions could put the sperm motility under control

The present study was conducted to evaluate the efficacy of the pH-shift process in protein recovery from whole and gutted common kilka and characteristics of the produced gel compared with muscle surimi obtained with the conventional method. Although both acidic and alkaline methods reduced total pigment (TP) in isolates obtained from the whole and gutted fish, the alkaline version was more effective and the lowest amount of TP was observed in the isolate from gutted fish using alkaline version. The last sample also contained the lowest amount of TCA soluble peptide which was significantly lower than the others. Also, gel produced from the isolate recovered form gutted kilka with the alkaline version had significantly higher water holding capacity and gel hardness but it was weaker than the sample obtained with conventional method. The results were supported with higher relative amount of actomyosin and actin in the structure of the gels produced from the gutted fish isolate and surimi from fish muscle, as reflected in SDS-PAGE. Nevertheless, the whiteness of the samples recovered with pH-shift process was quite lower than the muscle surimi which reveals the necessity of more research in this area.

The effects of using n-3 LC-PUFA -enriched Artemia nauplii and newly hatched Artemia on survival and resistance to pH stress in larvae of angel fish (Peterophylum scalar) were examined In tow 20 days period. In the first step of the experiment the larvae with an average weight of 0. 86 ±0. 03mg were fed with tow diets (enriched Artemia nauplii and newly hatched Artemia) for 20 days. At the end of the first step of the experiment، the significantly (p<0. 05) higher survival rate was observed in larvae fed with enriched Artemia (90. 66%) than the larvae fed with newly hatched Artemia (83. 66%). In the second step of the experiment the larvae with an average weight of 20. 03 ±3. 73mg were fed only with commercial diet for 20 days. At the end of the second 20th days of the experiment، larvae exposed at pH stress (including 5. 5، 6. 5، 8. 8 and 9. 5) for 96 hours. The Result showed that the larvae were fed with n-3 LC-PUFA-enriched Artemia have a higher significant survival rate than other group in the period of the experiment and pH stress (p<0. 05). Therefore، using of n-3 LC-PUFA-enriched Artemia recommended for increasing survival rate and the resistance to pH stress.

The anaesthetic effects of clove oil in juvenile common carp (8-12 g) were investigated under various water quality conditions, consisting of different pH and temperature. The time to loss the equilibrium, induction of anesthesia, equilibrium recovery and response recovery were measured. The results showed that clove oil induced the desirable anaesthetic condition in less than 3 minutes in all experiments. However the time of equilibrium recovery and response recovery were longer than 5 minutes in many cases.
When using clove oil at concentration of 100ppm, the most suitable anaesthetic effects and recovery times were observed at water temperature of 25C and pH=7 and 8, as well as at 30 C with pH=9.
No morbidity or mortality occurred during induction of anesthesia by clove oil and recovery of fishes.