Food Calorie Question

Good question! I assume as calorific value (in calories) is found by burning a weighed sample in pure oxygen and measuring the rise in temperature it causes in a surrounding water jacket, any burning of the item must reduce the calorific value slightly by virtue of some of the burning already having happened. Unfortunately it is very difficult to get a sensible answer on cooked v raw food calories as there is so much bro science on the net but I would guess unless some of the fat is extracted by cooking (for example pan frying a duck breast done properly releases a lot of duck fat) the values are more or less the same. It may be however that cooked food has more net calories as it doesn't use so much energy to process, but that's just a guess.

When you cook food (such as toasting bread) your are losing water not sugars.

Toasting bread is not cooking.

The bread went from raw to cooked when the bread was baked. Toasting it does not change anything. You're just warming it up.

Yes, there are differences between the nutritional values of cooked vs. raw food. In general, cooking denatures proteins and allows us to extract more nutrition more efficiently. It also makes some vitamins more bio-available. Other vitamins are destroyed by cooking -- it depends on the specific vitamin and the method of cooking.


See also:
http://www.slate.com/articles/life/food/2009/06/i_cook_therefore_i_am.html

(the book being discussed: http://www.amazon.com/books/dp/0465020410)

When you cook food (such as toasting bread) your are losing water not sugars.

Obviously, but if you burn it that converts sugars, carbs, protein, etc, into carbon so you do 'lose' them.

As to your comment about toasting not being cooking, let me provide you with the definition -

"cooking

Noun
The process of preparing food by heating it."

- note, nothing to do with converting raw food into cooked food. Left over dishes can involve a lot of cooking and are made from already cooked food.

We're not talking dictionary definitions of "cooking." We're talking biochemical changes when heat is applied to nutrients, and those come at certain temperature points and time points.

When it comes to toast? The big biochemical changes in the wheat happen when you bake the bread. The changes from toasting it are insignificant in comparison.

Same with assembling dishes from leftovers. When I make a frittatta out of leftover cooked veggies and eggs, the only thing that is undergoing a serious change via cooking is the eggs. The cooked veggies will not show any measurable change from being warmed up and encased in egg.

Sorry but there is a biochemical change when you toast bread. If you don't think so, try adding back the water and turning it back into bread

And re leftovers, what about Bubble and Squeak -

"Bubble and squeak is a traditional English dish made with the shallow-fried leftover vegetables from a roast dinner. The main ingredients are potato and cabbage, but carrots, peas, Brussels sprouts, or any other leftover vegetables can be added. The chopped vegetables (and cold chopped meat if used) are fried in a pan together with mashed potatoes or crushed roast potatoes until the mixture is well-cooked and brown on the sides. The dish is so named because it makes bubbling and squeaking sounds during the cooking process"

You cannot turn them back to their starting, cooked, state because this second cooking causes biochemical changes to the food, not least a certain amount of caramelisation. Cabbage fried after cooking tastes quite different to the plain cooked stuff.

But forget all that, the question was whether there is a calorie difference between cooked (however you define cooking!) and raw foods. It is not clearly defined from a scientific point of view and I'm not certain the calorific values will change unless something is lost or gained in cooking. And we'll probably never knows unless someone has done a comparative scientific experiment properly formulated to avoid errors.

The toast question was on my provincial nurses exam 28 years ago and the answer is "there is no caloric difference".

Yay! Thanks, that's about what I expected. Not sure about steak on a BBQ though...........