Abstract
ObjectivesApproximately 47% of ground beef purchased at local stores is susceptible to premature browning (PMB). Premature browning is a condition in which cooked ground beef patties will have a well-done appearance at temperatures insufficient to render ground beef patties safe. Various studies have shown that the form of myoglobin present in the interior of patties at the time of cooking can affect cooked color. However, limited studies have determined the role of metmyoglobin reducing activity (MRA) in cooked patties on cooked color.Therefore, the objective of this study was to determine the role of MRA in cooked color development and premature browning.Materials and MethodsFresh coarse ground beef chubs (85% lean, n = 6) were obtained from a local purveyor on the day of preparation. Coarse ground beef was fine ground using a LEM meat grinder. Patties (1 cm thickness × 10.5 cm diameter; 113 g) were prepared using a patty press. Patties were randomly allotted to vacuum (VP) or high-oxygen modified atmospheric package (HiOx-MAP, 80% oxygen and 20% carbon dioxide). High-oxygen modified atmospheric package patties were placed in Rock-Tenn DuraFresh rigid trays with absorbent pads and sealed with a clear, multi-layer barrier film using a semi-automatic Mondini tray-sealing machine and certified gas blends. Packaged patties were stored in the dark at 0 ± 2°C for 48 h. At the conclusion of storage, two patties from each packaging were cooked to either 65 or 71°C using a George Foreman. One patty from each packaging was utilized for lipid oxidation and raw MRA. Two extra patties were utilized to characterize d 0 (no packaging and storage) pH analysis, lipid oxidation, and MRA. Surface color (a*) and MRA of raw and cooked ground beef patties were measured. Nitric oxide metmyoglobin reduction method was used to determine the reducing activity of both raw and cooked patties. Surface color was determined daily using a HunterLab spectrophotometer. The experiment was repeated six times and the data were analyzed using the Mixed Procedure of SAS (SAS Inst. Inc., Cary, NC). The PDIFF option for protected F-test was utilized to separate least squares means (P < 0.05).ResultsThe average pH of ground beef was 5.73 ± 0.01. There was a significant packaging by temperature interaction for raw surface color and metmyoglobin reducing activity. High-oxygen modified atmospheric package patties had lower (P < 0.0001) cooked internal a* values and MRA compared with VP patties regardless of temperature. There was no difference in cooked patties MRA for HiOx-MAP between 65 and 71°C (P > 0.12). Cooked patty MRA decreased as temperature increased for VP patties (P < 0.041). There was a significant packaging × time interaction observed for lipid oxidation. HiOx-MAP patties had greater (P < 0.0001) lipid oxidation compared with VP patties after 48 h storage and d 0 patties. Storage did not affect lipid oxidation in VP (P > 0.40).ConclusionMetmyoglobin reducing activity in cooked patty suggests that enzymes involved in metmyoglobin reduction retain partial activity at greater temperatures. Developing strategies to increase reducing activity in ground beef has the potential to limit the incidence of premature browning.
Highlights
Cooked color is primarily due to the Maillard reaction and myoglobin denaturation
Highoxygen modified atmosphere packaging (HiOX-modified atmospheric packaging (MAP)) makes patties very susceptible to premature browning (PMB) compared with polyvinyl chloride (PVC) and VP
Suman et al (2009) noted that the interior of steaks packaged in HiOX-MAP were more brown than that of VP steaks due to greater pigment oxidation
Summary
Cooked color is primarily due to the Maillard reaction and myoglobin denaturation. the presence of either ferro- or ferrihemochrome will impart brown and red cooked color, respectively (Warren et al, 1996b; Lytras, Geilesky, King, & Ledward, 1999). Most of the consumers determine degree of doneness by checking the internal color of beef patties (USDAARS/FSIS, 1998; USDA FSIS, 1998; Killinger et al, 2000; Ralston et al, 2002). This can be a food safety concern as premature browning (PMB) is a condition in which ground beef patties will exhibit an internal brown and well-done appearance at temperatures lower than the USDA recommended 71.1°C to eliminate pathogenic bacteria (Hague et al, 1994; Hunt, Sørheim, & Slinde, 1999; USDA FSIS, 1998). The mechanism of PMB is not clear, research indicated that the myoglobin form present within the interior of patties can influence cooked color (Hunt, Sørheim, & Slinde, 1999)
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