Cooking Time for Twin Roasts
I am cooking 2 beef tenderloins, approximately 10 pounds in total for my in-laws in the same oven. I would like to know the proper cooking time to ensure two medium rare roasts. Please help!
Are they each 5 pounds, or is one 2-1/2 pounds and the other 7-1/2 pounds? Increasing the number of items in your oven doesn't dramatically increase the cooking time, but the size and shape of the foods matters a lot.
Getting a roast cooked through follows a fairly complex mathematical formula that is explained in detail in Peter Barham's The Science of Cooking (Canada, UK), and which we theoretically understand but not well enough to explain. It has to do with how quickly heat is conducted from the outside of the roast to the center, and that is a function of the roasting temperature, the initial temperature of the meat, and to a great extent, the shape and size of the meat.
Putting 10 pounds of meat in the oven instead of 5 pounds is not going to have much of an effect on the temperature in the oven. It may cycle on for just a teeny bit longer when the roasts initially go into the oven (particularly if the meat has recently come from the refrigerator), but if your oven is any good, it will maintain the roasting temperature you set. So getting the roasts cooked through is just a function of Dr. Barham's heat-flow formulas. And it won't take much longer to cook two roasts than one.
If this is a little more science than you need to feed your in-laws, why not follow James Beard's advice for roasting beef tenderloins? And if your in-laws are wondering what to put in your Christmas stocking this year (um, we really meant to say holiday stocking), why not drop a few hints about that instant-read thermometer you've had your eye on for quite a little while now? It will help relieve some of the guesswork.
The whole tenderloin is frequently used as a roast. It is either barded with fat and roasted or trimmed carefully of fat, brushed well with oil and butter, and basted frequently during roasting. While it is considered an elegant roast for important occasions, an eye of the rib roast or a shell roast has more flavor and makes just as handsome a presentation.
Fillets weigh from 4 to 10 pounds and have a coating of kidney fat on one side and a membrane that often runs the entire length of the cut. These should be removed before cooking. It is a fairly simple operation that anyone can do, even though his butcher may turn out a more finished product.
It is my belief that this roast and the eye of the rib, which are usually thin, without bone, and with little fat, cook better at high temperatures, such as 400°F to 450°F (205°C to 235°C). An average fillet takes about 35 minutes to reach the very rare state, which is what it should be. An eye of the rib may take slightly longer because of its greater thickness, but surely not more than 50 minutes. Test with a meat thermometer for an inner temperature of 120°F to 125°F (50°C to 52°C) for rare and 140°F (60°C) for medium rare. Salt the roast about 10 minutes before removing from the oven. Allow to stand 10 to 15 minutes before carving.
We don't know how your in-laws rate, but if they're among the really good ones, you might like to consider a slightly more elaborate presentation: Fillet of Beef Flambé.
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