Effect of packaging materials and gamma irradiation on color and microbial count of minced beef meat Investigations of minced beef meat packaged under vacuum during cold storage

Microbial growth, oxidation of lipids and color are important factors for the shelf life and, consequently, for the acceptance of fresh meat by the consumer. This research aims to extend the shelf life of minced meat using low doses of gamma irradiation during cold storage. Vacuum packed minced meat packed in a two-layer polyamide/polyethylene (PA/PE) film and multi-layer packaging materials (polyester/aluminum foil/polyethylene (PET/AL/PE), then exposed to irradiation in doses 0, 1.5, 3 and 4.5 kGy. During cold storage at 4 +/- 1 degrees C, the color and microbiological load of minced meat were evaluated. The results indicated that all samples irradiated at different doses greatly reduced the microbial count and prolonged their useful life up to 42 days at 4 +/- 1 degrees C compared with only 7 days for the control samples. Furthermore, the 3 and 4.5 kGy doses completely destroyed Staphylococcus aureus. Color of concern, the value of L* (lightness) increased when the storage time increased, while the values of a* (redness) and b* (yellowness) showed a gradual decrease on 7,14 and 21 days as storage time for the control sample and the vacuum packed sample. The lightness of all the samples increased with increasing periods of conservation. After 21 days, the irradiated samples began to decrease in brightness until the end of the storage period.