جستجوی مقالات مرتبط با کلیدواژه « Gamma irradiation » در نشریات گروه « دامپزشکی »

Aquatics, including fish, have always been one of the most perishable protein sources. For increasing storage time of the resource there are several ways including radiation.  The effect of gamma irradiation was investigated on the microbial load and total volatile nitrogen of fish meat rainbow trout (Oncorhynchus mykiss). At the beginning of these experiment, the fish meat is irradiated by 1.5, 2.5 and 3.5 KGry radiation doses and subsequently transferred to the refrigerator at 4°C. During the first, seventh and fourteenth days after irradiation (after transfer to the refrigerator) the total amount of bacteria and total volatile nitrogen was investigated. The results indicated a greatly reduction of amount of bacterial load and total volatile nitrogen by the use of various doses of gamma irradiation. Among the irradiated doses, 3.5 KGry showed the greatest decrease in these parameters, but considering that there was not huge difference between 2.5 and 3.5 KGry in the reduction, thus 2.5 KGry gamma irradiation is selected as a suitable dose for rainbow trout irradiation and subsequent storage in the refrigerator.

H9N2 subtype of avian influenza virus (AIV) is the most common strain of low pathogenic AIV in the Middle East. The aim of this study was to investigate the humoral and cellular immune responses of commercial layer chickens immunized with gamma-inactivated H9N2 AIV. For this purpose, 120 one-day-old chickens of layer breed were divided into four groups including 3 replicates and 10 birds per replicate. Vaccination of chickens was done on days 11 and 25 of age. The first and second groups received the irradiated vaccine (IV) by intranasal and subcutaneous injection methods respectively, the third group was injected with formalin-inactivated vaccine and the fourth group was not vaccinated as the control. Anti-H9N2 serum antibodies, proliferation rate of splenocytes and the expression levels of interleukins 2, 6 and 10 and interferon gamma in these cells were investigated. The results indicated that in the groups immunized with intranasal IV the level of HI titers at 25 days of age was significantly higher than those in other groups. Additionally, stimulation index of splenocytes in 39 and 85 days of age and the level of gene expression of all the measured cytokines, especially interferon gamma in splenocytes at 39 and 55 days of age was significantly higher compared to formalin-inactivated vaccine. Based on the findings of the present study, the use of H9N2 AIV vaccine inactivated by gamma irradiation could be considered as a good candidate in layer chickens because it could induce antibody responses and cellular immunity at the levels higher than the formalin-inactivated vaccine.

In this research, the effect of gamma irradiation, thyme essential oil (EO) and vacuum packaging treatments on fresh shrimp for a period of 15 days at 4°C during storage was investigated. For this purpose, two concentrations of EO (0.4 and 0.8% v/w) and two doses of radiation (2.5 and 3.5 KGy) were used. Treated shrimps and control sample were subjected to chemical (pH, total volatile basic nitrogen, free fatty acids, peroxide index, thiobarbituric acid reactive substances and color indexes), microbiological (bacteria total count, psychrophilic bacteria and  Escherichia coli) and sensory evaluation and analyses performed on certain days (0, 5, 10 and 15th) of storage. The obtained results showed that pH, FFA, peroxide, TBARS and TVB-N values of all treatments increased in the duration of storage, significantly (p<0.05). Microbial load in all treatments also increased over time. Bacterial growth delayed growing in samples by using of combination of thyme oil, gamma radiation and vacuum packaging. At first, adding thyme EO leds to decrease L* index, but at high concentration of EO (0.8%), color change was decreased significantly (p<0.05). The results of sensory evaluation showed that different treatments had significant effect on sensory parameters of shrimp (p<0.05). Finally, the shrimps treated with combination of vacuum packaging, 0.8% (v/w) EO and 2.5 KGy can be introduced as the best treatment.