3

If I microwave a piece of bread until all the water is evaporated and then weigh what is left, is the caloric content estimated by finding the calories in the same weight of flour?

10

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

5

It depends.

  • If your ingredients are just flour, salt, yeast and water, you’ll be reasonably close, but not really exact.
  • If you are dealing with a more complex recipe, added milk, eggs, sugar, fats, seeds... the values will be way less precise.

But: There’s always some deviation, even between different batches of flour, and all values you will find in books, tables, the Internet, will be a kind of average. You may assume that the differences even out over time and counting down to the last single calorie is except for very few special cases (where you would need a lab setup and scientific methods) less crucial than most people may assume.

3

No, because most store-bought bread is more than just wheat flour and water. Many kinds of bread contain quite a lot of sugar and other additives with non-negligible calories.

  • 1
    I know the bread I am talking about have no oil or sugar added – Ahmad Hani Apr 8 at 14:37
  • 2
    @AhmadHani if you know the ingredients and the amounts that you put in, isn't it easier to estimate the caloric content based on that? – JJJ Apr 9 at 0:13
  • Actually I didn't know the amount of water in that loaf so that is why I thought to dehydrate it. – Ahmad Hani Apr 9 at 15:58
  • @AhmadHani that could be estimated - for regular white bread, I‘d assume around 65% of the flour weight, then about 10% loss during baking. So about 60% of the flour weight in the finished bread. Values for whole-grain or some „artisan“ breads are higher, often around 75%. – Stephie Apr 10 at 9:00
1

Bread is not just flour, as already stated. It is flour that has undergone a variety of physical and chemical changes (even if we don't consider the other ingredient for simplicity's sake).

Those changes not only change the caloric content of the product (some may be exothermic, some are endothermic, meaning some lower and some raise the caloric content of the product).

It would be an interesting experiment to see the difference between the caloric content of a pound of flour as compared to a pound of bread created using that same flour.

  • 1
    The OP is asking about caloric content, and this is widely understood to mean the calories contained in a food, not the calories that the human body extracts after eating the food. All nutritional info labels, and the major nutritional epidemiology studies use the first one. The second one is not relevant to the question, and we always answer nutritional questions exactly as asked, without telling the OP what other parameters they might want to measure instead. – rumtscho Apr 9 at 10:35

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