So, have people always cooked ground beef up to 160F in order to assure the destruction of Escherichia coli O157:H7? The answer is no; up until the late 1980’s you could get a medium-rare hamburger in a sit-down restaurant. E. coli outbreaks, stemming from meat products, appear to have coincided with increasing speeds on large cattle-kill lines. E. coli is a fecal borne bacteria and since cattle often lay in manure, E. coli spores are expected to be part of the dingle-berries caked on hides. When mechanical pullers rapidly yank up, then down, on cattle hides bacterial spores are sent airborne to land on the nutrient rich sticky surface of hot carcasses. I remember reading an article in a meat magazine back in the early 1990’s where the owner of a small slaughter plant was questioning the 160F internal temperature recommendation for ground beef. She said something along the lines of, “So what their telling me is that it’s OK to eat shit as long as it’s fully-cooked.” Conveying hanging hot carcasses through steam cabinets and applying organic acid sprays are now routine proactive interventions against E-coli contamination.
Observing cured and/or smoked cooked meats tells us that heat is not the only color affecting factor. Uniform cured meat pigmentation is essential to the successful marketing of cured meat products. While a grey-brown fully-cooked color is expected in uncured meat items. Smoked uncured meat will sometimes display a smoke-ring due to oxygen having been occluded from the cooking chamber by thick smoke for long periods of time. Often a cure containing spice mix is rubbed on the outside of smoke-cooked roast to produce a faux smoke-ring. A submerged and/or lid covered pot roast can also lack sufficient oxygen to denature. I once made fresh Polish sausage then held it in freezer storage for later sale at a festival booth. When the sausage was cooked it remained pinkish toward the center and caused a lot of questions about the products doneness level. Leaf marjoram used in making the sausage contained natural nitrate. Over a period of time bacteria helped reduce the nitrate to nitrite, hence partially curing the sausage. Impurities in iodized salt and possible nitrate in sea salt can also cause a partial cured color in fully-cooked fresh meat products. High myoglobin (meat color pigment) levels in beef or older hogs, along with meat pH, also effects if meat will appear fully-cooked upon reaching the proper temperature to do so. Conversely, there is a condition known as premature internal browning (especially in ground beef products) that’s caused by the chemical state of myoglobin and/or the meat pH level. Unfortunately, if a wholesale or retail customer breaks open a pre-cooked beef patty to evaluate doneness, she or he likely won’t care anything about this discussion. Eye-appeal is buy-appeal and the customer has the final say as to what they will accept. It’s inexpensive and simple for home cooks to trust in a calibrated dial face meat thermometer; whose tip is placed in center of mass in the meat. Such thermometers are easy to recalibrate in ice water by turning the nut under the dial face. Practiced fry-cooks can accurately judge meat doneness (but, not internal color) by pushing on cooking products. Further, chefs might not like using thermometers because it takes time for them to register and because some meat juices run out when probes are removed. Infrared/thermal radiation thermometers offer a way to not probe cooking meat. Roasts can be temperature probed near the end of a cook then the probe can be left in until the meat stops cooking (rests).
Undercooking meat can be a food safety issue for both pork (very low risk of muscle worms) and beef. And, overcooking usually causes palatability issues. Even though the meat color occurrences covered here don’t happen often, nutrient-dense meat is expensive and so is wisely prepared having full knowledge of what to expect.