Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Effect of Combınıng Sous Vıde And Irradıatıon Technologıes

On The Shelf Lıfe of Fısh

The sous vide technology, which involves pasteurization and cold storage of vacuum packaged food, has become popular all over the world in recent years because of appealing to catering industry. However, there is still a risk about microbial activity in the products if the pasteurization conditions are not applied effective enough. It is well known that using a combination of more than one food preservation technique together is more effective than alone. Therefore, in this study irridiation technology which is known to be effective on the microbial activity is used together with sous vide technology to determine the effect on the shelf life.

After the sous vide treatment (70°C 10 min), mackerels were seperated into three groups as non-irradiated (control) and irradiated (2.5 kGy and 5 kGy), then stored in cold storage (2°C ± 1). Their sensory, physical, chemical and microbiological analyzes were done weekly. According to the sensory analyzes it is found that the non-irradiated control group and the group irradiated at 2.5 kGy could not be consumed at the 7th week while the group irradiated at 5 kGy could not be accepted at the 8th week.
The amount of total volatile basic nitrogen (TVB-N) exceeded the limit in the 6th week with the value of 32.31 ±1.08 mg/100g whereas in the irradiated groups the limits didn’t exceed in any week and it is also found that the difference between the control group with irradiated group was statistically significant (p<0.05) in 6th week. According to the thiobarbituric acid reactive substances (TBARs) analyzes’ results, the limit value exceeded at the first week in control group while it was exceeded in the first day in the other two groups in consequence of the fatty characteristic of mackerel and the effect of irradiation. The pH and trimethylamine nitrogen (TMA-N) values were not considered as an indicator of the quality because these values didn’t exceed the limit in any group. In microbiological analyzes total mesophilic and psychrophilic aerobic bacteria loads of the control group pointed out the deterioration of the product after the 6th week but bacterial loads of the irradiated groups didn’t exceed the limit during the storage period. The number of anaerobic bacteria in the control group showed significantly higher values than others in the later stages of storage. Microbiological analyzes’ results proved that the irradiation treatment enhances the microbiologic quality and provides more reliable of sous vide products. In this study the effects of combining sous vide and irradiation technologies on the shelf life were investigated and our results showed that irradiation of sous vide samples using 5 kGy gamma rays resulted in one week increasement of shelf life than other groups from sensory aspects.
Control samples deteriorated in 7th week of storage according to sensory scores. However, mesophilic and psychrophilic aerobic bacterial loads became very close to 6 log cfu/g in 5th week and exceeded this limit in the 6th week. The counts of anaerobic bacteria were also above 5 log cfu/g in the 5th week. In control group which was not irradiated, it was understood that the microbiological growth took place before sensory deterioration and it could be dangerous for consumers safety.
In irradiated groups, total number of mesophilic and psicrophilic aerobic bacteria was under the limit during the storage period and the number of anaerobic bacteria showed significantly lower values than control group. Therefore these results indicate that the sous vide packaged mackerels with irradiation treatment provide microbiologically safer consumption and supporting of sous vide packaging with irradiation treatment in terms of microbiological reliability can be recommended.