The current minimum required temperature for cooked beef, as set by the U.S. Department of Agriculture, is 145 degrees Fahrenheit. A rare roast beef attains an internal temperature of only 130 degrees. Different cooking methods will yield a rare result, but it is not possible to tell how cooked a roast is inside by looking at the outside, so use of a meat thermometer is essential.
You Say Rare, I Say Raw
Rare roast beef is red and cool, but not cold, which is extra-rare -- also known as blue or essentially raw -- in the center. The internal temperature of rare roast beef is approximately 120 to 130 degrees Fahrenheit. Medium rare is 130 to 140 degrees Fahrenheit. According to the USDA, neither of these preparations is safe; the agency recommends a minimum internal cooking temperature of 145 degrees Fahrenheit for any beef, the low end of medium, to eliminate E. coli and other all food-borne bacteria responsible for illness.
Rarified Air: Heat and Technique
Two leading schools of thought exist about how to get a perfect rare roast beef, and they use opposite extremes of cooking heat. One suggests cooking at 500 degrees Fahrenheit for five minutes per pound of roast, then turning off the oven and allowing the roast to coast to doneness via your closed oven's residual heat for about one additional hour. The other says to cook at 225 degrees for an hour per pound, until the roast is done. Hotter cooking prepares your meat more quickly, but it is not suitable for tougher cuts, which benefit from the tenderizing effects of a longer cooking process.
Roasts are too thick to use the basic touch test -- the firmer, the more well done -- that you can employ with steaks. Classic meat thermometers, comprised of a short metal stem and an analog readout, can require opening your oven or removing the top of your grill to see their readouts, resulting in heat loss and uneven cooking. A probe thermometer is the right tool for the job. With a thin, oven-safe wire leading to a digital readout, you are guaranteed perfect, rare results every time. Most probe thermometers have an alarm that will sound the moment your roast beef has reached your desired internal temperature.
Tips and Serving Suggestions
Remove roast beef from the oven when it is 5 degrees lower than your desired final temperature; its retained heat will finish the job. Cutting into a roast before it cools sufficiently and its juices have had a chance to redistribute is a common mistake. Once removed from the oven, leave it alone for at least 15 minutes before slicing to keep the meat juices in your roast and off your cutting board. A well-sharpened chef's knife allows for smooth, even slicing; a Cook's Illustrated test found that electric knives shredded rare roast beef when used to cut thin slices.
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