Effect of Oven Roasting at 200 and 300 ° F. on the Microbiology of Beef Roasts

Abbreviated Summary

I. SCOPE OF THE STUDY:

The purpose of this study was to determine the effect of oven roasting at 200 and 300⁰ F. on the microbiology of high and low finish rib and top-round beef roasts. Rib roasts averaged 10.2 and 6.7 pounds and top-round roasts averaged 6.3 and 5.5 pounds for high and low finish respectively. Roasts cooked at 200⁰ F. were heated to an end point of 152⁰ F. and roasts cooked at 300⁰ F. to 158⁰ F. Samples taken aseptically from the middle of a center slice of each of the forty roasts were analyzed microbiologically for the presence of aerobic microorganisms and clostridia.

II.PRINCIPAL FINDINGS

Roasts cooked at 200⁰ F. required significantly longer cooking time per pound than their pair-mates cooked at 300⁰ F. (P<.001 for high finish rib and top-round and P<.01 for low finish rib and top-round).

With the exception of two strains of Streptococcus faecalis that were recovered from a high finish rib cooked at 200⁰ F. and from a low finish top-round cooked at 300⁰ F., the hypothesis, that there would be sufficient lethal heat under the conditions of this study to kill all nonsporeforming microorganisms, appears to be acceptable. Cooking times at both 200 and 300⁰ F. provided large margins of safety for the destruction of staphylococci and Salmonellae, which are often causative agents of food poisoning.

All microorganisms were recovered at low levels. This study indicated that roasting at 200⁰ F. as a means of increasing tenderness of beef cuts proposes no additional microbiological hazards over roasting at 300⁰ F., a conventionally accepted temperature for roasting beef.