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Dec 11, 2013 02:05 PM

Fermentation & honey/sugar in yeast bread recipes

In yeast-raised breads, the yeasts digest the carb from the flour. If the dough contains a sugar, e.g. table sugar, honey, etc., isn't that digested ahead of the starch? So aren't yeast breads containing a sugar less sweet than you;d expect from the amount of sugar put in?

Does anyone know the biology of this stuff?

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  1. Yeast cannot digest starch, the prevalent carbohydrate in flour. Rather, specific enzymes (called "amylase") act on the starch in the flour and break it down over time into simpler sugars.

    These enzymes are, IIRC, present in very small amounts in most type of grains, but most flour manufacturers add a small percentage of malted barley -- which has a large amount of the enzymes -- to the mix in order to increase the activity and give the flour enough conversion power to raise a loaf of bread without any added sugar.

    So, getting back to your question: Initially the yeast will begin consuming the added sugar, as it will be the only available energy source. But in the meantime those enzymes are still going to be acting on the flour and converting the more complex carbohydrates into sugars, thereby replacing some of what has already been consumed.

    How much sugar remains in the final product after full fermentation will depend upon how much yeast is added to the dough, how fresh/active the yeast is, how fresh/active the enzymes in the flour are, and fermentation temperature.

    So will you taste the difference? Highly unlikely. Bakers yeast is not a very efficient sugar consumer, especially when compared with various ale and wine yeasts. And the amount of time that bread is allowed to ferment isn't that great anyway. Therefore I think that you shouldn't worry too much about this particular issue.