Can I find out the caloric content of bread by dehydrating it?
Conventionally, drying is only the first step.  The second is burning it and seeing how much energy is given off.

But this isn't always the best way to determine the calories that your body gets from the food, as it doesn't deal with bio-availability - basically, can your body extract that energy from the food?

Diet foods often cellulose or other fiber added to them -- which can burn and have heat, but your body can't absorb.  So for nutritional reasons, they're considered 0 Calorie.

For the case of unenriched bread, we basically have only a few ingredients ... water, flour, yeast, and maybe salt.  Once we remove the water, the yeast and salt are lower percentages, so we can estimate (stress estimate), but we also need to know what type of flour was used.


whole wheat flour : ~339 kCal / 100 grams
white flour : ~364 kCal / 100 grams


(but this is likely for American whole wheat, which is white flour with bran mixed back in, not ground up whole wheat berries)

Of course, it's also worth mentioning that calorie counts on menus and food packaging in the US are only estimates.  There are tables of calories per item, and they just add them up in the amounts used to get a number. (so all wheat bread is considered to have the same kCalories/gram, no matter how it was made)  Some of those values might just be estimates based on the ratio of carbohydrates, fat, and protein in the ingredient.

But how something is cooked, and the particular person (their gut biome, how well they chew, etc.) can affect how much energy they can get from the food, so it's always going to be a really rough estimate