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The word “cooking” implies that you heat things up. But how much? Clearly the temperature is important.

By comparison with other technical issues around cooking, temperatures are relatively straightforward. There's the Celsius scale (water freezes at 0° and boils at 100°), and the Fahrenheit scale (water freezes at 32° and boils at 212°). The obsolete Réamur scale and the technical Kelvin scale are not used in cooking. Celsius is still frequently referred to as Centigrade, since it has 100 degrees between freezing and boiling.

Fahrenheit gets on my nerves because I'm not used to it, but it's relatively easy to convert to Celsius: C = (F - 32) * 5 / 9. When I feel like it, I might include a conversion table here.

But how do you measure temperatures? In days gone by, you guessed, probably based on some related factor like surface colour or the length of time cooking. Both are not very good indications, but with practice you can get things right, at least until you change some parameter. If you need 50 minutes to cook a 2 kg chicken in the oven at a specified temperature marking (ovens vary wildly in the accuracy of their thermostats), how long do you cook a 3 kg chicken? Or how long do you cook it in a different oven?

Clearly there has to be a better solution, and there is: measure the temperature where you're interested in it, inside the food (usually meat), with a thermometer. There are two main issues with meat thermometers: the devices available, and how to use them: what temperature are you aiming for, and where? No object warms up completely evenly, and if you measure the right temperature in the wrong place, there's a good chance that the results won't be what you want.

The devices

Meat thermometers have been around for a while. The older ones are analogue, usually with a dial, though I've seen glass ones filled with spirits. Mercury is poisonous, and there's a danger of a thermometer breaking in the meat; that's probably one reason for the dial-type thermometers. The ones I have found in Australia recently have left much to be desired. Some are even made of plastic (“do not place in the oven”). The best I've found looks like this:


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The scale is in Fahrenheit, with Celsius conversions (66, 71, and other unlikely values). The best thing about it is the warning at the bottom: Do not put in water. My old thermometer, made in Germany, does not have this inscription:


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But at least this thermometer has a scale in Celsius, and it's relatively fine-grained (even if it is off by nearly 10°; but you can compensate for that sort of thing). It also has a much smaller sensor, which is good for the food:


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Nowadays digital thermometers seem to be the way to go, but there are cautions there too. This is the first one I bought:


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It's useful (and not overly expensive), but it's not easy to use. The temperature probe (in front) is coated with metal, and it is connected with a wire braid. I presume that the sensor itself is at the tip of the probe, but the metal cover is a good conductor of heat, and as a result it tends to show higher temperatures than you'd expect. That's why I've wrapped some stiff paper around it, to insulate it from the outside. A ceramic covered probe would be much better. It would also have avoided the fate of this particular unit: I put the probe in a barbecue with the lid down, and it fried the probe (presumably the cable). But I needed to find a better unit anyway.

The next one I bought was from IKEA. It looks quite similar to one illustrated in Bonniers Kokbok. Maybe it's a relatively common design in Sweden:


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It doesn't seem to have the same issues as my first digital thermometer, and it has a magnet on the back that makes it possible to attach it to the fridge next to the oven. About the only issues I have with it is that the sensor is rather slow to react, and that you can't turn off the beeping it makes when you hit the set temperature.

Cooking temperatures

What temperature should a roast beef be in the middle? Ask me and I'd say 58°. Ask others and they might come up with something else, assuming they know any temperature at all. The Americans seem to be particularly keen on higher temperatures— Wikipedia includes an “updated temperature” column which effectively redefines such terms as “medium rare” and “rare”, apparently based on a “fact sheet” from the US Department of Agriculture. What good that does is beyond me. Possibly it's the US equivalent of our bad language. Other US sites are more reasonable, though for some reason it gives higher temperatures for lamb than for beef.

One important example where temperature control is cooking whole chickens. Underdo them and the thigh meat is still red, and it's difficult to get it off the bone. Overdo them and the breast turns to cardboard.

But what temperature? Where do you measure it? The canonical answer, and the one that I found in the only two cookbooks I have that mention such things, is in the thighs, where the chicken cooks the slowest. Bonniers Kokbok recommends a temperature of 70°. The other one (I forget which, but it was English or Australian as opposed to US American) specifies 75-80°. The about.com page recommends 165° to 175°F, or between 74° and 79°, but doesn't say where. The problem is that I've tried this before (in fact, going to 88°, which is what I recall from the charts on my old analogue thermometers), and I continually got underdone thighs.

I've decided that the real issue is the exact placing of the probe, and possibly the fact that it's not specific enough, and the thermometer is too influenced by the temperatures of the looser space around the bone, which gets cooked first. Today I decided to measure in the breast. There are a couple of reasons: first, it's larger, so the danger of incorrect readings is less, and secondly, it's the most likely to be overdone. I took it out at 82°, and the results were much better, but still not quite enough. I'll try 88° in the breast next time.


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