Doctoral Dissertations

Date of Award

3-1980

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

J.T. Miles

Committee Members

S.L. Melton, H.O. Jaynes, C.C. Melton, W.R. Backus

Abstract

Ninety-five steers were grouped into 19 quintets on the basis of breed, weight and body type. One steer of each quintet was finished on a silage-limited grain ration (TT) and another of each quintet was finished on a grain ration during the 1978 winter (T2). The other three steers were wintered on pasture and in April 1978, one of each quintet was finished either on orchard grass, fescue and clover pasture (T3), a limited grain ration (T4) or a full grain ration (T5) during the 1978 summer.

Ground beef containing approximately 20 percent fat was prepared from the semimembranosus muscle and brisket fat of the left side of each carcass. Simple carbohydrates, free amino compounds, fatty acid composition of neutral and polar lipids, flavor score, moisture and fat content were determined for ground beef prepared from steers in T1 through T5. Bacterial count was determined for ground beef prepared from T3, T4 and T5. Changes in simple sugar content and free amino compounds were studied as a function of frozen storage time on T3, T4 and T5. Flavor profile, volatile analysis of heated lyophilized water extract and Hunter color for raw and cooked patties were studied for ground beef prepared from 18 Hereford steers, 6 each for T3, T4 and T5.

No significant difference was found for moisture or fat content among treatments. Ground beef from the low energy level T3 and T4 had a higher population of psychrophilic and lipolytic bacteria than ground beef from high energy T5. Ground beef from summer, grass-fed steers (T3) had less sugar, lower flavor score and higher linolenic acid in neutral and polar lipids. Other differences in the fatty acid composition of neutral and polar lipids among treatments were also observed. No significant differences among treatments were found for free amino compounds. There was an increase in free amino compounds and a decrease in simple sugar content during frozen storage time.

A dairy or milky flavor which was observed by the flavor profile panel in grass fed beef was particularly unpleasant at higher intensities. Also, there was a lack of beef fat flavor in grass-fed beef. No significant qualitative or quantitative differences were found between volatiles of heated lyophilized water extract of ground beef prepared from grass-fed steers and that of grain-fed steers.

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