Doctoral Dissertations
Date of Award
8-1982
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Food Science and Technology
Major Professor
Curtis C. Melton
Committee Members
M. J. Riemann, J. T. Miles, K. W. Jeon, Sharon L. Melton
Abstract
Ninety-one Angus steers which were wintered on fescue pasture and allowed unlimited grazing on an orchard grass, fescue and clover pasture during the spring and summer of 1980 were assigned to 5 groups of 15 steers each and one group of 16 steers on the basis of frame size. One group was slaughtered off pasture (0 days on corn), and the rest were adjusted to a whole shelled corn diet for 2 weeks. After adjustment, a group of corn-fed steers was slaughtered every 28 days up to 140 days. For each steer, the fatty acid composition of total intramus-cular lipids of the longissimus, brisket fat and intermuscular fat was determined, the volatile fatty acid (VFA) content of the longissimus was measured, and the flavor of the cooked longissimus was evaluated by Quantitative Descriptive Analysis. Most of the fatty acids in each fat site were affected by days steers were fed corn. As days steers were fed corn increased, the percentages of saturated fatty acids in the brisket and intramuscular fat decreased, the percentages of monounsaturated fatty acids of all three fat sites increased, and the percentages of the polyunsaturated fatty acids of the brisket fat and intramuscular lipid decreased. Frame size of steers did not affect the fatty acid composition of any fat site very much. Of the three fat sites, the intramuscular lipid had the greatest concentration of polyunsaturated fatty acids, the seam fat had the most monounsaturated fatty acids, and the brisket fat had the highest amount of saturated fatty acids. The VFA content of the longissimus muscle also was affected by days steers were fed corn. Steers fed corn for any time generally had greater concentration of acetic, isobutyric, butyric and caproic acids and lower amounts of valeric acid in the longissimus than steers off pasture. Of all frame sizes, steers with the largest frame size had the lowest levels of isocaproic acids and highest levels of acetic acid. As corn was fed steers from 0 to 140 days, the intensity of an undesirable milky-oily aroma and flavor decreased linearly and the intensity of a desirable cooked beef fat aroma and flavor increased linearly. Long chain polyunsaturated fatty acids (C18:3, C20:3, C20:4, and C22:5), αC15:0 and C18:0 were positively correlated with the milky-oily aroma and C10:0, C12:0, C14:0, C14:1 and C18:1 were negatively correlated. The polyunsaturated fatty acids are more labile to oxidation during storage and cooking of meat, and probably contribute to the off-flavors in beef produced by grass and to its reduced storage life.
Recommended Citation
Yeo, Young K., "Beef flavor and fatty acids in different carcass sites as affected by grass and corn diets up to 140 days. " PhD diss., University of Tennessee, 1982.
https://trace.tennessee.edu/utk_graddiss/7843