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I'm on a low-carb diet and would like to know if caramelizing an onion increases its carbohydrate content. I'm primarily interested in "net carbs," so dietary fiber that's converted to sugar would qualify as increasing the carbohydrate content as far as I'm concerned.

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up vote 3 down vote accepted

Since dietary fiber is made mostly of cellulose that isn't broken down during cooking I don't think it should be an issue. The browning that occurs is from the proteins and sugars already in the onion.

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That makes sense, but why does the onion become sweeter then? Is it just that the sharpness of the onion is removed, leaving the underlying sweetness? Or is something converted into sugar (maybe starch? meaning no change is total carbs I suppose)? – Anthony DiSanti Jul 11 '11 at 3:33
Going off the cuff here, but IIRC sulfur compounds are what give onions their "heat" when raw and are contained within the cell walls. By breaking down the cell walls via heat these compounds are released thereby letting the underlying sweet sugars to be more pronounced. A good demonstration is if you taste some onion that has been steamed in the microwave versus some of the same onion raw. Even though there isn't caramelization, some of the sulfur compounds have been allowed to escape via the steaming process resulting in a sweeter taste. – AaronN Aug 23 '11 at 18:35

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