In three separate trials, the visually and instrumentally determined color of patties cooked either fresh, frozen, or after thawing was evaluated. In trial 1, the effects of thawing and packaging were evaluated. The internal color of patties cooked to 71°C within 12 h of thawing at 7°C remained red-pink. Only after thawing for 18 h or longer did cooking to 71°C result in a well-done appearance. The color of patties thawed while vacuum packaged and then cooked was more red than the color of non-vacuum-packaged patties after cooking. Spectral analysis of the raw product indicated that the effects of thawing and packaging on cooked color were linked to the level of metmyoglobin (metMb); higher levels of metMb resulted in a less red patty color after cooking. In trials 2 and 3, the metMb level was varied by storage and/or processing conditions. Differences in the metMb level before freezing seemed to decrease during freezing and thawing. Differences in metMb before processing did not significantly (P > 0.05) affect cooked color. Patties cooked from the frozen state were less red than those cooked directly after processing. After 24 h of thawing, patties cooked to 71°C were brown, irrespective of metMb level. Premature browning, i.e., the appearance of patties being well-done at temperatures lower than 71°C, only occurred in thawed patties. After 24 h of thawing, patties appeared well-done at 65°C. It is concluded that handling, other than internal temperature, strongly influences cooked beef patty color. Therefore, the color of cooked beef patties should not be used as an indicator of internal temperature.
† Current address: Department of Food Science and Technology, University of Tennessee, P.O. Box 1071, Knoxville, TN 37901-1071.
‡ Reference to a brand or trade name does not constitute endorsement by the U.S. Department of Agriculture.