A prime rib is a little like a turkey: you probably cook only one a year, usually for an important occasion such as Christmas. Although you know there are alternative cooking methods that might deliver a better roast, they’re too risky. You don’t want to be remembered as the cook who carved slices of almost-raw standing rib or delayed dinner for hours waiting for the roast to finish cooking. Rather than chance it, you stick with the standard 350 degrees for X minutes per pound. A roast cooked this way, you decide, will at least not embarrass you.
Other than using general terms like juice and tender, I wasn’t sure how to define the perfect prime rib. So after consulting my many cookbooks, I came up with a dozen or so fairly different methods to cook prime rib. Although there were minor issues, such as whether the roast needed to be tied or whether it should be roasted on a rack, one big question needed answering: At what temperature should prime rib be roasted?
I started with oven temperatures. Suggested roasting temperatures ranged from a tepid 250 degrees to a bold 425 degrees. Other recipes recommended an initial high-temperature sear (450 to 500 degrees), then reduced the oven temperature to a more moderate 350 degrees for actual roasting.
All my prime ribs roasted at oven temperatures exceeding 300 degrees looked pretty much the same. Each slice of carved beef was well-done around the exterior, medium toward the center, and a beautiful, pink medium-rare at the center. I might have been tempted to say that roasting temperature doesn’t matter much if I hadn’t tried cooking prime rib at oven temperatures under 300 degrees. The results surprised me, although it certainly wasn’t love at first sight.
About halfway through the cooking time, my first roast at 250 degrees looked virtually raw, the internal temperature registered 110 degrees, and very little of its fat had rendered. But I quickly changed my mind as soon as I carved the first slice. This roast was as beautiful on the inside as it was anemic on the outside. Unlike the roasts that I typically cooked at higher temperatures, this one was rosy pink from the surface to the center – the juiciest and most tender of all the roasts I had cooked. This was restaurant prime rib at its best.
In addition to being evenly cooked, the prime rib roasted in a 250-degree oven had another thing going for it: Its internal temperature increased only a degree or two during its resting period. Roasts should normally be allowed to rest when they come out of the oven both to distribute the heat evenly and to allow the juices to reabsorb back into the outer layer of the meat. A roast cooked to 128 degrees, for example, moved only to 130 degree after 45 minutes rest.
Not so with the roasts cooked at higher temperatures. Their internal temperatures increased much more dramatically out of the oven. As a matter of fact, I noticed a direct correlation between oven temperature and the increase in the temperature of the roast while resting. Prime ribs roasted at moderate temperatures (325 to 350 degrees) increased, on average, 14 degrees during resting. In other words, if pulled from the oven at a rare 126 degree internal temperature, these roasts moved up to a solid medium (140 degrees) by the end of the resting period. Meanwhile, the prime rib roasted at 425 degrees increased a whopping 24 degrees (from 119 to 143) during its rest.
In addition to its more stable internal temperature, prime rib roasted at 250 degrees lost less weight during cooking than prime rib roasted at higher temperatures. A 6 3/4 pound roast cooked in a 250 degree oven weighed just over 6 1/4 pounds when it came out of the oven, a loss less than half a pound. By contrast, similar roasts cooked in a 325 degree oven lost just more than a pound, while roasts cooked at 350 degrees lost 1 1/2 pound. A prime rib cooked at 425 degrees lost a shocking 2 pounds. Part of the weight loss is fat, but certainly a good portion is juice. So a beef roasted 250 degrees clearly is juicer than a roast cooked at high temperatures.
And do not be concerned, low-temperature roasting is as safe a cooking method as higher temperature roasting, especially if you brown the roast first, which should kill any bacteria on the exterior. And though the odds of finding bacteria inside a prime rib roast are close to nil, the only way to guarantee a bacteria-free slab of prime rib is to cook it to an internal temperature of 160 degrees, no matter what cooking method is used, low temperature or high. Unfortunately, at 160 degrees, the meat is gray, though, and unappetizing.
As nebulous as the meaning of “perfect prime rib” has been to me, it became crystal clear the moment I carved off that first slice of low-roasted prime rib. I immediately recognized it as the beef you get at a great prime rib restaurant. As it turns out, many such restaurants slow-roast their meat. They use special ovens that roast the meat at 250 degrees until it reaches an internal temperature of 120 degrees. At that time, the oven heat is decreased to 140 degrees, causing the meat’s internal temperature to increase to 130 degrees and remain there until ready to serve (up to 24 hours later). Unfortunately, few home cooks can use this method since most home oven thermostats do not go below 200 degrees. But by following these directions, home cooks can very closely approximate the superb prime rib served in the country’s best restaurants.
For a simple prime rib recipe, please click HERE