UBC Theses and Dissertations
Effect of electron-beam irradiation and vitamin E fortified diet on ground beef quality preservation Poon, Patty Wai Bing
The effects of electron-beam irradiation (EBI) treatment and dietary vitamin E supplementation on microbial and organoleptic quality of ground beef patties were investigated during 21 days refrigerated (4°C) and 6 months frozen (-22°C) storage. Ground beef patties were prepared from meat from cattle fed basal (diet I) and vitamin E supplemented diets (diet II). Plasma vitamin E concentration in cattle fed diets I and II were 1.58 ± 0.42 and from 2.49 ± 0.53 to 2.91 ± 0.57 μg vitamin E/ml plasma, respectively. Patties were then processed with 4 different doses of electron-beam irradiation (0, 2, 5, 10 kGy). Microbial indices monitored at 3-day intervals throughout a 21-day storage period at 4°C and at 1-month intervals during a 6-months storage period at -22°C, included Total Aerobic Plate Count (TAPC), Psychrotroph Counts and Total Coliform and E. coli Counts. Total aerobic and psychrotrophic bacterial growth in ground beef patties stored at 4°C and -22°C were significantly (P < 0.05) reduced by EBI at 2 kGy. Complete inhibition of bacteria occurred at 5 kGy or higher (P < 0.05) dosages of EBI. Beef patties made from steers fed vitamin E (diet II) were found to have a higher (P < 0.05) TAPC and Psychrotrophic bacteria than patties derived from animals fed the basal diet (diet I). From the growth pattern of the two detected classes of microorganisms, psychrotrophic bacteria appeared to recover faster from irradiation stress, and were able to grow more rapidly upon storage than the aerobic bacteria. Neither Coliforms nor E.coli were not detectable in the beef samples during the experimental period due to a low initial count. Parameters such as pH and water activity (a[sub w]) were also measured. Chemical and instrumental indices monitored at 3-day intervals throughout a 21- day storage period at 4°C, and at 1-month intervals during a 6-months storage period at - 22°C included thiobarbituric acid reactive substances (TBARS), color, and texture. Moisture, total crude lipid content and fatty acid compositions were monitored at 7-day intervals throughout a 21-day storage period at 4°C and at 1-month intervals during a 6- months storage period at -22°C. Results indicated that irradiation was associated with higher (P < 0.05) TBA values and greater (P < 0.05) shear force. TBA values of beef patties reached peak levels on Day 9 in 4°C storage and at Month 3 in -22°C storage, respectively. No significant differences were observed in shear values of beef patties irradiated at different doses. With all four levels of irradiation, Hunter a values of beef patties decreased (P < 0.05) significantly, and this effect could be observed immediately after irradiation. Lipid oxidation was significantly retarded in stored beef patties derived from cattle fed vitamin E (diet II). These results indicate that electron beam irradiation pasteurization is an effective method to ensure microbial safety of refrigerated and frozen ground beef patties. The application of electron beam irradiation and vitamin E supplemented diet significantly improved ground beef safety and lipid stability during storage at 4°C and -22°C.
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