time versus temperature

[Anna N]

Wondering if there is such a thing as a time-temperature conversion chart. Have searched the web but found nothing relevant. What I am looking for is something that would tell me that if I lower the oven temperature by 25F how much time should be added to a recipe to compensate. I realize there's optimum temperatures and certainly wouldn't want to fool around when baking! but when I need to add a side dish and it requires a different oven temperature than say, the main dish, how do I compensate. Thanks.

[oraklet]

i, too, would like to see such a chart (though i realize it can't be very precise). how long, for instance, to cook a chicken at 70C?

[Dave the Cook]

You might find this helpful:

The Little Book of Meat

This is from the site of fellow eGulleter Bouland. I don't know if it's exactly what you're looking for, but I remember browsing a bit and finding it pretty interesting.

[Anna N]

You might find this helpful:

The Little Book of Meat

This is from the site of fellow eGulleter Bouland. I don't know if it's exactly what you're looking for, but I remember browsing a bit and finding it pretty interesting.

Not quite what I was after but a most interesting read, nonetheless.

[g.johnson]

If the conditions obey Newton’s law of cooling (which covers heating too) then it’s straightforward to show that cooking time is given by

t = ln((T0 – Toven)/(Tfood – Toven)) / k

where Tfood is the desired temperature of the food, T0 is the initial temperature of the food, Toven is the oven temperature and k is a constant that depends on the size and shape of the food. So if t1 is the cooking time at an oven temperature of T1 then the cooking time at oven temperature T2 will be given by

t2 = t1 ln((T0 – T2)/Tfood – T2) / ln((T0 – T1)/(Tfood – T1)

This will be rather inexact as it doesn’t take into account temperature gradients within the food but should give you some idea. I would buy a thermometer, though.

[Anna N]

t2 = t1 ln((T0 – T2)/Tfood – T2) / ln((T0 – T1)/(Tfood – T1)

Damn! I knew I should have paid attention in algebra. Thanks, I'm sure the formula would work but I failed grade 2 math! In fact, I am seriously math-challenged and get nearly psychotic at the very thought of an equation. I'll take two Valium and see what I can do with this. Seriously - your efforts to answer my question are appreciated.

[Fat Guy]

G: Every oven has different thermal properties because of the mix of convection, conduction and radiation that accounts for heat transfer in cooking. (In other words, I don't think Newton's law of cooling adequately explains how an oven works.) Even the same oven, with its convection fan switched on or off, can give two radically different performances at the exact same ambient temperature (20 to 50 percent faster in many cases). So probably the best we could do is create a relative scale or a chart that works for one oven.

[g.johnson]

In fact, I am seriously math-challenged and get nearly psychotic at the very thought of an equation.

If you feel comfortbale doing so, send your email address to g.johnson@physics.org, and I'll send you an Excel spreadsheet that'll do the calculation.

Fat Guy: Newton’s law applies equally to convection and radiation and the differences in heating efficiency in any given oven would be reflected in the constant k in my first equation. As long as the oven has a reasonably stable temperature then I think it should be OK from that point of view. I’m more concerned that my equations assume that propagation of heat through the food is much faster than transfer of heat from oven to food. In other words it should be pretty accurate for predicting heating in a bar of copper, I’m not so sure about meat.

[tommy]

Fat Guy: Newton’s law applies equally to convection and radiation and the differences in heating efficiency in any given oven would be reflected in the constant k in my first equation. As long as the oven has a reasonably stable temperature then I think it should be OK from that point of view. I’m more concerned that my equations assume that propagation of heat through the food is much faster than transfer of heat from oven to food. In other words it should be pretty accurate for predicting heating in a bar of copper, I’m not so sure about meat.

and of course a pizza stone helps.

[Anna N]

Found at least the beginning of the kind of table I was looking for. It was on, of all things, a packet of Lipton Side Kick's:

For this particular product, they give the following options:

425 F (220C) for 35-40 mins

375F (190C) for 40 mins

350F (180C) for 45 mins

325F (160C) for 55 mins

From this I guess one can extrapolate to some extent.

Thanks for all the input.