Why Must Ground Beef Be Cooked At 155 F

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Browning Before a Safe Temperature is Reached

Ground beef patties that have been cooked may seem brown before they are done internally. This is mostly brought on by the fresh ground beef pigment’s extensive oxidation, which can happen, for instance, when frozen ground beef is allowed to thaw slowly or when thawed ground beef is stored in a refrigerator.

A ferrous iron-oxygen complex is created when the ferrous iron in ground beef’s myoglobin pigment is exposed to air. When myoglobin is not oxygenated, it has a purplish-red color. When iron combines with oxygen to form oxymyoglobin, the color changes to red. This is what gives fresh beef its red color. However, meat loses one electron to become ferric iron if it is kept for extended periods of time, kept above recommended temperatures, or exposed to excessive air. The resulting ferric pigment, known as metmyoglobin, is brown.

According to Lynch et al. (1986), consumers tend to associate bright red color with high quality. Therefore, they are often concerned when ground beef has a red exterior and a brown interior. This coloration may be explained by varying degrees of oxygenation both inside and on the surface of the meat (the grinding process allows air to contact more surface area of the meat) Ground beef will turn grayish-brown if it comes into contact with air, such as the inside of the package. Similarly, ground beef may prematurely brown if it is stored for even a single day (USDA-ARS/FSIS, 1998).

Ground beef turns from red to pink to brown when it cooks. The meat won’t change color while cooking if it is already brown. Certain ground beef patties appear well-done at internal temperatures as low as 131 °F, according to recent research (Hague et al, 1994; Hunt et al, 1995; USDA-ARS/FSIS, 1998).

Additionally, the color of raw meat from older carcasses may be less red or darker, giving the impression that it is cooked enough when it is still undercooked. It has been discovered that patties cooked to 131 °F have a color similar to patties cooked to 140 °F when ground beef patties are made from a combination of older and younger carcasses. It has been demonstrated that patties cooked to 150 °F and those cooked to 160 °F are visually identical (Hague et al, 1994).

FSIS conducted a survey to determine the frequency of premature browning in cooked ground beef after reviewing previous studies. Ground beef from different parts of the nation was used to make the patties that USDA researchers cooked. Over 25% of the newly ground beef patties prematurely turned brown (with “prematurely” being defined as below the safe temperature of 160 °F). Results of USDA research were presented at a public meeting in Arlington, Virginia on May 27, 1998, and they confirmed the Agency’s recommendation that color is not a reliable indicator of doneness. To ensure that ground beef patties reach 160 °F, consumers should use a food thermometer (USDA-ARS/FSIS, 1998)

Even with controlled cooking procedures, the USDA researchers discovered significant variation in endpoint temperature and color between and within beef patty formulations. As a result, it can be challenging for customers to tell whether ground beef patties are cooked through if a food thermometer isn’t used during the cooking process.