[Cidtalk]

Cidtalk  asked the Naked Scientists:
   
Hello,
I love your show. I listen while I work 12 hour shifts in a data centre in Missouri, USA.
 
My question is about calories.
 
If calories are determined by how much energy it takes to burn them, after cooking butter, oil, sugar, etc. have some of the calories burned away? In other words, does combining and cooking food change the calories in each ingredient or the dish as a whole?
 
If a unit of sugar = 100 calories and a unit of flour = 100 calories and then you use them as ingredients in a recipe like cookies, after the process of baking and cooling the cookies, would the combination still = 200 calories?
 
Thanks very much,
Cindy Hayes

What do you think?

[Bill.D.Katt.]

I would think that it would just be like that, simple addition. Of course if you cook something like corn in water then pour off the water, some of the sugars are lost, this would decrease the calorie count. In food preparation where you add sugar and the sugar is consumed by bacterium, the calorie count would probably decrease. A calorie is of course the amount of energy required to increase 1g of water by 1 degree C.

[Bored chemist]

There can be losses during cooking, but these are generally small. Caramelising sugars and browning proteins (like the brown colour of toast, rather than bread) also reduces the availability of the calories. If you add wine to a cooked meal part of the alcohol will boil off and so those calories are "lost".

On the other hand, some foods are a bit  indigestible when raw and cooking them will increase the effective calorie content.