Gamma irradiation can be used as one of the most effi cient methods to reduce microorganisms in food. The irradiation of food is used for a number of purposes, including microbiological control, insects control and inhibition of sprouting and delay of senescence of living food. The aim of this study was to study effects of gamma irradiation, refrigeration and frozen storage as the combination process for improvement of red meat shelf-life. The bovine meat samples were treated with 0, 0.5, 1, 2 and 3 kGy of gamma irradiation and kept in refrigerator for 3 weeks and in freezer for 8 months. The control and irradiated samples were stored at 4-7˚C and at -18˚C for refrigeration and frozen storage, respectively; and microbial and chemical analyze was done at 1 week and 2 months intervals. In this study the optimum dose of gamma radiation in order to decrease the total count of Mesophilic bacteria, Coliforms, Staphylococcus aureus and especially for elimination of Salmonella was obtained at 3 kGy. Microbial analysis indicated that irradiation and storage at low temperature had a signifi cant effect on the reduction of microbial loads. There was no signifi cant difference in chemical characteristics during freezing storage in bovine meat. Also, irradiated meat samples (3 kGy) were stored in 4-7˚C for 14 days, compared to 3 days for non irradiated samples.
Ionisation chambers are the most practical and important radiation measurement devices due to their high sensitivity and relatively constant response with wide range of applied potential. In this work, a new plane-parallel ionisation chamber is proposed using carbon nanotubes as sensing electrodes. Some characteristics of the new chamber such as cable effect, leakage current and reproducibility are investigated. The polarisation effects, besides voltage effect and linearity are also verified. All tests are performed using a 60Co gamma radiation source. The obtained results are compared with that of a standard ionisation chamber (PTW Roos W34001 plane-parallel ion chamber) and international code of practice on dosimetry (i.e. IAEA TRS No. 381).
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