Why does the carbs / fiber ratio decrease after cooking?
According to USDA, medium grain raw brown rice has carbs and fiber at a ratio of 76g / 3.4g = 22.4.
When cooked, the ratio changes to 24g / 1.8g = 13.3.
Are these numbers wrong, and if not, why does this ratio change in favor of fiber? Mere dilution shouldn't change this ratio.
EDIT: The missing 0 hypothesis seems to be the most plausible explanation so far, but I'd like to find sources completely independent from USDA to be sure. All of the sources I found just copy USDA directly or indirectly.
Best Answer
When you cook things using water you add mass that have 0 calories. Some food, like rice, absorb that water. Hence boiling 100 grams of rice increase final mass to around 300 grams.
Then again you measure the 100 grams carbs and it's 3 times less than your starting points because you never added additional carbs in the process.
The fiber amount is IMHO wrongly calculated because 3,4 gram divided by 3,16 (ratio of carbs in 100 grams before and after cooking) is 1,075. Probably someone rounded up the 75 wrong and had 1,8 instead of 1,08.
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How does cooking affect carbohydrates?
Starch molecules which are the main source of calories in many diets when heated in an aqueous or moist environment, swell, rupture and burst and starch gets gelatinized and this permits greater enzymatic digestion by enzymes like Amylases. Cooking thus increases the digestibility of carbohydrates.Does cooking decrease carbohydrates?
Cooking changes the Glycemic Index of carbohydrates but does not alter the amount of carbs. Particularly Potato and Plantain vegetable are changed of its GI drastically after cooking. So there are people who drink Plantain shakes instead of Banana shakes.Does cooking break down fiber?
The process of cooking food breaks down some of its fibers and plant cell walls, making it easier for the body to digest and absorb the nutrients ( 17 ).Does fiber in food cancel out carbs?
Healthy carbohydrates such as fruit and vegetables are usually high in fiber, while processed carbohydrates typically lack fiber. While fiber does not cancel out carbs, high-fiber foods are typically digested slower, which makes them less likely to be stored as body fat.Mayo Clinic Minute: Low-carb diet findings and cautions
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Answer 2
It's likely that the brown rice was boiled and then drained; some of the starch would leach out into the cooking water and be removed with it, while the insoluble fiber would remain in the rice.
Additionally, note that NAL's nutrition data was taken from various sources over a long period of time. It's possible that the data for raw and cooked rice was taken at different times, from different brown rice cultivars. (I doubt that this was the primary source of the difference, though.)
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