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Cooking and Oven Load
Name: J. Agnew
Status: educator
Age: 20s
Location: N/A
Country: N/A
Date: Thursday, November 28, 2002
Question:
To help settle a friendly debate, my friends and I were
hoping you could answer a question regarding heat in an oven: if a
person were to put two things in an oven to bake, would it take longer to
cook those two things, at the same temperature, than just one thing at
that temperature? Example: one pie in the oven's cooking time versus 2
pies in the oven's cooking time. Is heat shared in an oven?
Replies:
Johanna,
Oven cooking simply involves bringing the items to be cooked up to a certain
(set) cooking temperature and then holding them at that temperature for a
specified time. How quickly the first step can be achieved depends on the
mass (mainly the water content) of the food to be cooked and on the oven's
capacity to maintain the set temperature.
Once the food is at the set temperature, all that's required of the oven is
the capacity to maintain the temperature in the face of ordinary thermal
losses through its interior to the surroundings. Ordinarily, the second
factor -- maintaining the set temperature -- is well within the capacity of
most ovens.
It is the mass of the food -- and its initial temperature -- when it is first
placed in the oven that determines how long it takes for the food to reach
the set temperature. A small room-temperature dessert pie will heat through
much faster than a large room-temperature pie. Also, whether or not the thing
to be cooked is frozen will have a significant effect on the time it takes
for it to reach the set temperature.
Now you and your friends can discuss the issue and come to your own
conclusion.
Regards,
ProfHoff 525
When you place an object in an oven the heat will be transferred from the
oven's internal environment to the object. The oven has a thermostat that
keeps its temperature fairly constant, no matter what is placed in it
(within reason). As long as the objects in the oven don't absorb so much
heat that the oven cant keep up (or are so big as to prevent even
circulation, it is unlikely that the number of things placed in the oven
will affect the cooking time. It will take more heat to cook more mass that
is placed in the oven, so the flame will be on more.
Peter Faletra Ph.D.
Assistant Director
Office of Science
Department of Energy
Dear Johanna,
Cooking in a conventional oven is not slowed when you put more things into
it. Two pies will cook at the same time as one pie. This will also work in
a convection oven, although you have to be careful not to impede the air
flow of the fan, then things will cook unevenly. The only time cooking time
is increased is when you are cooking in a microwave oven. As you know, 4
baked potatoes in the oven will take longer than 1 baked potato. This is
due to the fact the microwaves are "exciting" the water molecules in the
food to cook them from within. Given that the wattage on your oven does not
change, cooking a more massive quantity of food will slow down the cooking
as there are only a given amount of microwaves generated.
So that is that! Now go out and bake a bunch of pies in your oven and have a
bunch of friends over to celebrate this new found knowledge!
Martha Croll
I think it depends on what the items are and how efficient the oven is. I
think two pies in a standard oven with adequate heat distribution and
circulation would be fine time-wise. I would wonder about two turkeys or two
hams though--not only would oven circulation be compromised, but I think
these two big pieces of meat would take longer to heat up, and require more
cooking time, in the same way that a large pot of water takes longer to boil
than a small pot with the same flame setting.
Pat Rowe
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