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Often when you buy meat from the store it comes with guidance on how long the meat needs to be roasted, presumably calculated as a function of its weight. Is there some well known general algorithm for calculating how long to roast various types of meat (e.g. for display on packaging).

Perhaps something like: roasting time = c * weight of meat

Assuming the algorithm is this simple, is there some reference of ideal oven temperatures and scaling constant c for each type of meat (chicken, beef, pork etc)?

Relatedly, is there a well known set of algorithms for converting between say, fan oven, AGA, gas mark standards for oven temperature?

I'm assuming these facts must be well known in meat supplier's product development departments, due to the labelling I see on meat that I buy. However having Googled it a fair bit I can't find these details summarized anywhere.

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any commentary on the reason for the downvote? – leonigmig Jul 30 '12 at 10:01
up vote 7 down vote accepted

I don't know the whole algorithm, but I found the formula you'd need to derive it.

First, as you said, you would need a reference for the final internal temperature of the meat. McGee On Food And Cooking is a good source, I don't know of any online accessible ones, although they probably exist.

Second, you have to calculate the time needed to reach that temperature. The system of equations you need is (assuming a simple case - I am sure that adding oil to the pan, or breading the meat, or using a microwave will all change it a lot):

equations for heat transfer in meat

No, I don't know what these variables stand for. The book from which I scanned this uses it as an example why asking for such an algorithm is pointless. I guess you could look it up in the paper cited below the equations, if you are so inclined. I will stick with my thermometer.

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One word: Science. – BaffledCook Jul 30 '12 at 11:38
I accepted this answer because it accepts that such an algorithm exists, then goes on to show it is too complex for reasonable use. – leonigmig Aug 1 '12 at 12:09
This is the best "yes, but it's not practical to use" answer I've seen in a long time. – BobMcGee Aug 1 '12 at 14:18
I'd just note that when I took a heat transfer course in college years ago, I actually had to perform a calculation somewhat like this as a homework exercise. Even with all sorts of simplifying assumptions (roast was a perfectly symmetrical cylinder, composition of meat, density, water content, etc. was perfectly even throughout, etc.), it still took a couple pages of rather advanced math to get an answer. For all practical purposes, there is no algorithm, since you'd need perfect knowledge of the shape and external/internal physical characteristics of every cubic millimeter of the meat. – Athanasius Jul 1 at 21:06

What would "ideal" mean? Most items that you can roast in 2-3 hours can also be thrown in the slow cooker for 10-12 hours. It depends entirely on how the dish is prepared, how much fat/water you're using, whether or not you incorporate steam or convection, and more.

Anyway, if there were such an algorithm, it would be highly inadvisable to try using it at home, due to the huge variation in freezer temperatures, refrigerator temperatures, oven temperatures, rack positioning, how and where and for how long it was thawed, whether or not you open the oven door, etc.

In fact, if you happen to come across any cooking times that are based on weight, ignore them, because the weight is probably being used as a proxy for thickness, which is normally what matters in an oven.

There are many, many areas of the culinary arts where ratios and formulas are useful or even critical (especially baking and mol-gas) but cooking time isn't one of them. Please, just use a thermometer and the USDA temperature chart. That is how you cook meat safely; as long as you do that, it really doesn't matter what the oven temperature is or how long it's in there.

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Right, the cooking time to a particular temperature is proportional to the square of the thickness, I believe. – Michael at Herbivoracious Jul 29 '12 at 16:53
you make several excellent points, and the USDA link is really useful. but, are you really saying that heuristics in this area are totally impossible? – leonigmig Jul 29 '12 at 16:54
@leonigmig: A food thermometer is an heuristic. You're taking an approximate temperature measurement, in a piece of meat that may or may not have uniform temperature, and the target temperature is itself based on an estimated rate of heat transfer and an exponential, probabilistic microbial heat death function along with some conservative estimates about the baseline (raw meat). Why create yet another proxy when you can just measure the food temperature directly? Any such "algorithm" would have to be conservative enough to overcook your food 99 times out of 100. – Aaronut Jul 29 '12 at 21:52

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