Low-temperature baked roast

Photo by Laura Louise Grimsley on Unsplash

Meat baked in the oven is called a roast for some reason. The convective heat of the air in the oven heats the exterior of meat, and then heat from the exterior diffuses into the meat by conduction. Doing this in a ‘hot’ oven (~180C) also dehydrates the surface and triggers browning reactions[see ] that give a pleasing flavour. For the pedantic, it’s being baked, but not roasted.

However, because heat diffuses into the meat from its surface, there is a gradient of doneness from the surface to the core. A medium-rare temperature is ~55C, medium ~60C, and ‘well’-done ~65–70C. Not a big difference for a noticeable difference in texture. The core might be at one of these temperatures, but the surface will be near oven temperature (180C). So the meat ends up with a large range of doneness in cross-section between these temperature extremes. The resting phase attempts to even this out by letting heat in the meat equilibrate, although core temperature will continue to rise as a result.

Sous-vide solves this problem by cooking the meat at 55C (for example), so that the whole piece ends up medium-rare.

In the absence of a circulating water bath or water oven, something similar can be approximated in the home air oven.

Ovens don’t usually go as low as 55C though, and because of air’s poor heat transfer property, this would not work anyway — it would take too long and the meat would slowly dehydrate instead.

But it’s still possible to reduce the temperature gradient in the meat somewhat:

1. Starting with a cold piece of meat, sear it all over in a hot dry pan to brown. If the meat is lean, rub some oil into the meat rather than the pan (this is just to minimise splattering). It’s cold in order to minimise heat flow into the meat during this searing stage. It can even be semi-frozen. If the meat sticks, its best to just leave it alone. It will free itself as browning proceeds. It sticks because of an affinity between proteins in the meat and iron in the pan. Meat proteins tend to bind iron (which is why they are red).

2. Place the meat on a rack over a pan, and then into a 110C oven. The rack is just to allow air convection around the whole piece of meat.

3. Wait until the interior temperature reaches about 10C below what you are aiming for. So, for medium-rare, wait until it reaches 45C. How long this will take depends on a lot of factors, and with experience it may be possible to guess this. But for now, it is best done with a probe thermometer. Be sure the probe is scrupulously clean. Allow at least 60m.

4. Turn the oven off, but leave the meat in the oven. After about 30m the temperature in the centre of the meat should have risen to 55C (because of residual heat in the outer layers migrating to the core). Heat diffuses to the centre because it conducts better into the moist meat than into the surrounding air.

That’s it really. The same can be done with smaller cuts such as a thick steak. If aiming for medium-rare or medium, set the oven to 80C rather than 110C.

It’s all a matter of preference of course. For some, the highlight of a baked roast is the flavorsome, crunchy and browned exterior, and the condition of the interior can be sacrificed to achieve this. While the pre-sear does create a nice exterior, low-temperature baking can’t compete with the high-temperature approach for a browned exterior, but it will produce a more evenly cooked interior. So that’s the trade-off.

The browning reaction is called the ‘Maillard Reaction’ after the chemist who first described what was happening (around 1910). High heat, usually above 130C, breaks down proteins into amino acids that react with carbohydrates (free or bound sugars) in the meat. This produces more complex molecules that in turn react with themselves in an ongoing process that keeps adding flavour and complexity until it approaches the burned phase. It differs from caramelisation, which occurs only with sugar as the sugar molecules combine and recombine with themselves to produce new flavours. Among others, the Maillard reaction is responsible for the flavours of baked bread crust, chocolate and coffee, as well as all meats — ingredients that are not predominantly sugar. They are more complex than caramelisation because of the added contribution of the amino acids (adding atoms of nitrogen and sulphur to the mix).



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Science of cooking, eating and health. Retired neuroscientist.