Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Committee Chair(s)

Daren P. Cornforth


Daren P. Cornforth


Donald V. Sisson


Charles E. Carpenter


Von T. Mendenhall


Randall D. Weidmeier


Joseph M. K. Irudayaraj


Extra lean (3.3% fat) and lean (20.0% fat) hamburgers in three pH groups (≤ 6.0; 6.01-6.49; 6.50-6.92) were evaluated for cooking-temperature profile, total process lethality, and physical properties after cooking to 71°C by double-side frying on an electric grill. Neither cooking-temperature profile nor cooking time was affected by hamburger fat content or pH. Double-side frying to 71.1°C internal temperature was adequate for more than 6-log destruction of viable E. coli O157:H7 and Salmonella at the geometrical center of extra lean and lean hamburgers. The coldest spot was on the circumferential surface, as indicated by the presence of a red ring of undenatured myoglobin, and confirmed by the finite-element temperature distribution model.

The effect of pH (5.80, 6.29, 6.73) on myoglobin denaturation in extra lean (3.3% fat) and lean (20.0% fat) hamburgers was studied. Compared to normal meat (pH= 5.8), raw extra lean ground beef of pH = 6.73 had significantly lower oxidation-reduction potential (ORP) value, lower concentration of metmyoglobin after 48 hr of refrigerated storage, and more distinct cherry-red color. Percent of myoglobin denaturation during cooking was affected mainly by pH and was not affected by total pigment or fat content of hamburgers. A pH ≥ 6.5 and ORP ≤ -200 mV were characteristic of dark-cutting beef

In a third experiment, extra lean (3.5%) and lean (20.0%) beef patties were made from normal beef (pH= 5.70) and dark-cutting beef (pH = 6.60). Controls were made with no additives or with 1% salt and 10% added water. Various browning agents (1% glucose, 0.2% caramel colorant, 0.3% calcium peroxide, or 2.5% encapsulated lactic acid) were added with 10% water and 1% salt. Salt had a pronounced prooxidant effect on myoglobin. Distinctive absorption peaks at 541-548 nm and 577-582 nm indicated that the undenatured pigment in cooked patties was oxymyoglobin. Dark-cutting patties had more rubbery texture and slightly perceptible off-flavor. Patties with lactic acid were less juicy and had lower intensity of beef flavor than other patties, and moderate intensity of sour off-flavor. Addition of salt and encapsulated lactic acid to beef patty formulation could solve the problem of hard-to-cook patties.