Calories

[237SJ]

I was in Pret a Manger the other day, reading the calories in all their foods and it got me wondering. How does one determine how many calories are in a food? I know what calories mean in terms of energy but how does science quantify how many calories are in for example, an avocado? Is there some kind of experiment undertaken in a lab where it`s heated up in a test tube or something?
I couldn`t have any of their foods because I`m on Weightwatchers and had to have a measly cereal bar while my friend tucked into a lovely sandwich :-(

[237SJ]

Damn, I meant to put this in science.

[lankeela]

Good question, I wouldn't have seen it in Science. Often wondered this myself.

[Old_Geezer]

I assume they must have burnt the different foodstuffs in test tubes at some point and measured how much energy they got out of them ? Something like that'd be my guess.

[ChuckFickens]

Spot on, OG.

Did you not do the burning foods experiments and seeing how much it would heat a specific volume of water experiments at school?

http://en.wikipedia.org/wiki/Calorimeter

[bookbinder]

This might explain (although I don't understand it):
http://en.wikipedia.org/wiki/Food_energy

[smilingcrow]

Yes they measure the amount 1g of each individual food raises the temperature of 1cm cubed of water and work out the calorific value that way. Then it is just scaling it. I could go into much more detail but I would bore your pants off. Now unless you are a very atractive lady then I dont want to be doing that now do I?

[237SJ]

Thanks for your answers
smiling crow - I don`t wear any!
(only joking)
Chuck - No, I don`t remember doing that at school. That would have been far too interesting...