Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Animal Science (Animal, Dairy, and Poultry Sciences)

First Advisor

Kenneth W. McMillin

Abstract

The shelf-life of ground beef in modified atmosphere packaging (MAP) with exchange of gases before retail display was compared with conventional vacuum packaging (VP) and overwrapping with polyvinylchloride film (PVC) for display. Ground beef patties in MAP with distribution gases of 20% $\rm N\sb2:80\%\ CO\sb2,\ 50\%\ N\sb2:50\%\ CO\sb2,\ or\ 80\%\ N\sb2:20\%\ CO\sb2$ and display gases of 80% $\rm O\sb2:20\%\ CO\sb2,\ 50\%\ O\sb2:20\%\ CO\sb2:30\%\ N\sb2,$ or 20% $\rm O\sb2:20\%\ CO\sb2:60\%\ N\sb2$ had decreased weight loss, microorganism growth rate, metmyoglobin formation, and color degradation compared with patties in VP-PVC. Increased CO$\sb2$ during distribution retarded microbial growth. Display gas mixtures with higher O$\sb2$ increased redness (HunterLab "a" values), decreased metmyoglobin formation, and minimally increased lipid oxidation during six days of retail display. Ground beef patties in 50% $\rm N\sb2:50\%\ CO\sb2$ for distribution and 80% $\rm O\sb2:20\%\ CO\sb2$ for display provided optimal shelf-life and color in this study. An abusive display temperature (15$\sp\circ$C) decreased shelf-life of ground beef patties in VP-PVC and MAP (50% $\rm N\sb2:50\%\ CO\sb2$ exchanged for 80% $\rm O\sb2:20\%\ CO\sb2)$ to 1 and 3 days compared with 3 and more than 4 days with 7$\sp\circ$C display. Abusive display temperatures increased incidences of pathogenic microorganism species in MAP samples. Lipid peroxidation in ground beef and isolated microsomal fractions increased time after packaging in both VP-PVC and MAP with 50% $\rm N\sb2:50\%\ O\sb2$ exchanged for 80% $\rm O\sb2:20\%\ CO\sb2.$ Enzymic lipid peroxidation activity of microsomes extracted from the ground beef at each sampling time increased with extended display time after gas exchange, but lipid oxidation in beef patties remained constant during retail display. High $\rm O\sb2$ display gas increased HunterLab "a" values and reduced metmyoglobin formation in gas exchanged MAP samples without increasing lipid oxidation. MAP with gas exchange increased shelf-life compared with conventional VP for distribution and air permeable retail packaging for ground beef, but temperature is an important control of pathogenic microorganism growth.

Pages

206

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