فصلنامه شیلات
سال هفتادم شماره 3 (پاییز 1396)

Defrosting methods are the issues that affect quality and shelf life food, including fishery products. Therefore, this study investigated the effects of different thawing methods (refrigerator, water, air ambient temperature, and microwave oven) on chemical and physical [total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), pH, Water Holding Capacity (WHC), loss drip(DL) and hardness] analyses of frozen filet silver carp and the results obtained were compared with each other. The levels of TVB-N, TBA, WHC, DL, hardness of thawed samples together difference significantly, .But pH were not significant differences between treatments. Minimum (%59.45) and maximum (%64.95) WHC were by refrigerated and water thawed samples and microwave thawing samples had the highest DL (11.73) and hardness (3.85). Also, the highest TBA (1.65) and TVB-N (19.21) were observed in the thawing of samples by refrigerator, considering that the best results of the experiment were observed in water samples by thawing, so the thaw method is suggested as the best way to thaw Silver carp

The present study compared the geometric morphometrics of Barilius mesopotamicus populations in Diala and Tigris river basins in Iran. For this purpose, 99 fish specimens were sampled from Meymeh, Changooleh, Kangir and Doyrej rivers. Pictures were taken from the left side of the specimens and digitized using 15 landmarks placed on two-dimensional images using Tpsdig2 software. The data after Procrast analysis were analyzed with PCA, CVA multivariate statistical methods and cluster analysis. Geometric morphometric comparisons PCA and CVA tests and classification of the population and patterns of the body shape along the axes, showed some differences which were due to differences in head size and shape, body height and length of the caudal peduncle. Although the PCA and CVA tests did not fully differentiate the populations, Kangir was shown as a separate group.

Unicellular algae as phytoplankton are the important, effective and cheap sources in larvae and aquatic organisms feeding. In this research, assessment of growth rate, pigments contents, total sugar and protein in two species; Dunaliella salina and D. bardawil were studied in three nutrient mediums; Ramaraj (R), Johnson (J) and Shaish (S), during 24days. øFor all mediums, cells growth rate in 1M NaCl was higher than that in 2M and about two times in D. salina compared to that in D. bardawil. The effect of medium kind on cell division, almost observed with the highest in J, S and R, respectively. In 1M, the highest specific growth rate of alga was observed at S and J and in 2M, it was occurred at J, during 8 days. The volume of D. bardawil cells was two times more than D. salina cells and the highest was observed at 2M and S for both species. The changes in fresh and dry weights showed an ascending pattern along with the time, especially in S and J, which was higher at S. In 1M D. bardawil, the highest amount of total carotenoid on the basis of per ml and per dry weights, was observed in S and R mediums, respectively. The changes in beta carotene content by salt concentrations treatments and kind of medium was similar to total carotenoid. The highest amount of total chlorophyll per ml in S and J mediums and the highest amount of this index per dry weight was observed by R treatment. The highest effect for protein increment was related to J which was different from the higher induction effect of R in total sugar production. Totally, these findings suggest the significant effect of medium kind and salt concentration on the increment of nutritional substances in salt water unicellular alga, in addition to the species kind.

Due to the potentiality and rapid spoilage of edible aquatic, many technologies have been developed to increase their shelflife. In this research, the effect of modified atmosphere (40% carbon dioxide and 60% nitrogen), vacuum and air atmosphere packaging on the physical, chemical and microbiological changes of Oncorhynchus mykiss fillet during refrigerated storage (4°C) were studied. Chemical (total volatile base nitrogen (TVB-N) and thiobarbituric acid (TBA)), physical (pH, drip loss and colorimetry) and microbial parameters (total bacterial count (TVC) and psychrotrophic count (PTC)) were measured at 0, 3, 6, 9, 12, 15 and 18 days. The results showed that the fillets packed with modified atmosphere maintained the quality and pysical properties of fillets for 15 days. While the quality and pysical properties of control samples strongly decreased (P

One of the major causes of undesirable texture and color formation in fresh­ water fish surimi is the higher percentage of dark muscle in comparison to the muscle of the species of marine fish. In this study, the hydrogen peroxide factor in 1%, 2%, 3% concentrations, during different washing cycles (1, 2 and 3) in 1:2 and 1:3 ratios of water to mince was used to study their effects on texture, microstructure and water holding capacity and silver carp surimi gel. The results showed that during one washing cycle, the surimi gel texture had a higher cohesiveness at ratio of 1:2 compared to 1:3 (P0.05). In terms of two washing cycles, treatment of 1% H2O2 in the ration o 1:2 was chosen as the superior treatment, since, in addition to optimum gel strength, the lower percentage of hydrogen peroxide and lower volume of water is needed for washing. The same result was obtained during three washing cycle. In accordance with the punch test result, the WHC data showed a descending trend by increasing of washing cycles at higher percentage of H2O2 in both ratios of 1:2 and 1:3. Considering the result of the punch test, minimum volume of wash water, SEM of the best surimi gels at each washing cycle prepared and compared to the treatment of 3% H2O2 in the ration of 1:3 after three washing cycle as the worse treatment. As a result, application of 1% hydrogen peroxide in ratio of 1:2 during three washing cycle and result in a quality surimi gel from Silver carp mince.

Pollutants such as heavy metals are found in the nature in little amount, but their concentrations have increased in aquatic ecosystems e.g. the Caspian Sea due to increasing population and industrialization. Marine invertebrate like bivalves can absorb heavy metals from surrounding environment transferring them to upper level of trophy network. Hence, they can be considered as proper biological indicators to assess heavy metal pollutants because of being sessile and their sensitivity to accumulation. This work was conducted to study filtration rate of Mytilaster lineatus exposed to Cd (62 and 620 µgl-1) and Pb (6.2 and 62 µgl-1) and its ability to remove these metals from water. The experiments were carried out in a designed mesocosm system. The results showed a significant different in filtration rate of M. lineatus exposed Cd and Pb. Mytilaster lineatus revealed a higher filtration rate exposed to Pb concentrations in compare to that of Cd and also can be a proper biological index to assess Cd of aquatic ecosystems.

In this study, the effect of chitosan extracted from Metopenaus affinis was investigated in five treatments of 0, 0.5, 1, 1.5 and 2% on the shelf life of grass carp (Ctenopharyngodon idella) fillets in vacuum packaging for 15 days at refrigerator temperature. Chemical parameters of sp (pH, TVB-N, TBA, PV, FFA) and microbial count (TVC) as well as tissue properties, including hardness, cohesion, elastic, gum and chewing factors were measured. The results showed that there was a significant increase in pH during the storage, and in all treatments, changes were significant on day 15 compared to the zero day. By the 12th day, the amount of peroxide increased. The amount of TBA was exceeded at the 9th, 12th and 15th days except in the 2% chitosan treatment (on day 9). The amount of volatile nitrogen basic in the 15 days increased and from day 9 all treatments (except 2% chitosan) were desirable. The amount of microbial count of control treatment was eliminated on days 12 and 15. In addition, the results showed that chitosan had no significant changes in tissue properties (P>0.05). The results showed that the grass carp fillet with 2% chitosan coating until 15 days had a good quality.

Marine algae, like other photosynthetic plants, are exposed to a combination of light and oxygen that lead to the formation of free radicals and other strong oxidising agents. Absence of oxidative damage to their structural components suggests that they contain protective antioxidative compounds. The aim of this study was to evaluate the effect of green algae Ulva intestinalis powder on antioxidant activities of pasta. Pasta was prepared with algae as an ingredient at different levels (%5, %10 and %15). In vitro antioxidant properties, total phenolic content and DPPH scavenging analyzed. The results showed that pasta with 15% algal powder had the highest phenoilc content, antioxidant activity and radical scavenging activity (P

The objective of this study was to evaluate a non-lethal sampling technique to detect Streptococcus agalactiae, the bacterial pathogen causing Streptococcosis, in the blood and mucus of the infected rainbow trout, Oncorhynchus mykiss. Detection was established by PCR protocol based on the scpB gene. Also biochemical identification method was set by API strepsystem and conventional bacteriological tests. The fish were infected by intraperitoneally (i.p.) with 8×107 CFU/ml colony forming units of S. agalactiae. The PCR and biochemical method were positive for the blood samples from 3th and 4th days after exposure up to the end of the experiment while the fish look healthy. Mucus samples in PCR assay and biochemical methods were not positive until the end of the experiment. All any biochemically positive results were positive in PCR protocol, but some PCR positive results were negative in biochemical method. PCR Sensitivity tests were done in fish tissues seeded with serial dilutions of pure culture of S. agalactiae. Mucus was not efficient when the bacteria count is low. This study revealed that a nonlethal blood sampling can be used with high efficiency primers for PCR protocol to detect S. agalactiae in asymptomatic fish.

The present study was aimed to remove the organophosphorus pesticides diazinon and malathion from artificial water body using clay particles and activated carbon as the absorbents in a bit-trap system, and algae absorbent in a bio-treatment system. Physical treatment system, the bit-trap system, contained two separate but related tanks with sheath media to tap extra materials; and also received specific amount of montmorillonite clay and activated carbon in daily schedule. Bio-treatment system was also equipped with Cyanophyceae species. microalgae on the sheath media. Pesticides in two different concentrations (10 and 1000 mg/L in physical, and 6 and 60 mg/L n biological systems) were added to the treatment system. Study duration was 10 days, and daily water sampling was conducted to evaluate concentration of the pesticides and pH. Results showed that physical treatment system was successful to remove the pesticides with the reduction efficacy of 64% and 48%, and 68/7% and 41/3% for 10 and 1000 mg/L diazinon and malathion, respectively. After 10 days, bio-treatment system was also reduced the amount of pesticides with the 68/3% and 71/6%, and 40/5% and 67/8% for 6 and 600 mg/L diazinon and malathion, respectively. In the both treatment systems, pH was gradually increased along with the removal of pesticides. These results represent the efficacy of bit-trap system as a suitable medium for the absorbents which removed the major amount of pollutants. Also, the results of this study provide a reliable backbone of the role of micro-algae in water treatment from pesticides.