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 influences of lipid peroxidation and pigment autoxidation in beef and liposome model systems were examined in modified atmosphere packaging containing oxygen (O$\sb2).$ Ground beef of 75 and 90% lean were packaged in 80% nitrogen (N$\sb2){:}20\%$ carbon dioxide (C$\sb2)$ for distribution and storage atmospheres were exchanged for 80% $\rm O\sb2{:}20\%\ CO\sb2$ at 15, 18, 20, 22, 25, 27 or 29 days postpackaging before retail display. On the same postpackaging day, samples from longer gas exchange, but shorter display times had lower lipid oxidation, psychrotrophic growth, metmyoglobin formation, discoloration and odor scores when compared with samples from shorter gas exchange times and longer display times. Model systems of liposome, myoglobin and myoglobin-liposome were stored in 100:0, 80:20, 60:40, 40:60, 20:80 or 0:100 O$\rm\sb2\%{:}CO\sb2$ with $\beta$-carotene and $\alpha$-tocopherol at 0.01, 0.0001 or 0 M. Higher O$\sb2$ increased myoglobin and lipid oxidation in myoglobin-liposome systems. Lipid stability with no antioxidants was less in myoglobin-liposome than in liposome systems and metmyoglobin formation was greater in myoglobin than in myoglobin-liposome systems. $\alpha$-Tocopherol retarded oxidation of myoglobin in different model systems and gaseous atmospheres. Oxymyoglobin, hydrogen peroxide and superoxide anions were quantified in deoxymyoglobin, oxymyoglobin and metmyoglobin solutions stored in air at $\rm 4\sp\circ C.$ Oxymyoglobin linearly decreased with time in oxymyoglobin solutions and was the highest in deoxymyoglobin solutions at four hours. Superoxide anions were highest in metmyoglobin solutions, followed by oxymyoglobin and deoxymyoglobin solutions. Superoxide anions increased after four hours in deoxymyoglobin solutions, corresponding to the oxymyoglobin decrease. Myoglobin-liposome, myoglobin and liposome systems were packages in 80% $\rm N\sb2{:}20\%\ CO\sb2\ and\ 80\%\ O\sb2{:}20\%\ CO\sb2.$ Oxymyoglobin decreased to a greater extent with increased time in myoglobin-liposome than in myoglobin systems. Oxymyoglobin stability decreased more rapidly in 80% $\rm N\sb2{:}20\%\ CO\sb2$ than in 80% $\rm O\sb2{:}20\%\ CO\sb2$ during 12 hours. Liposome presence favored release of superoxide anions from myoglobin with high O$\sb2.$ Lipid peroxidation and myoglobin autoxidation increased with increased O$\sb2$ when both lipids and myoglobin were present. Superoxide anion generation was highly related to myoglobin oxidation and hydrogen peroxide production, which was attributed to phospholipid oxidation.

Pages

203

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