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Food Science: Why Some Flour Gets Bleached and Bromated

2009-04-07-BleachedFlour.jpgAfter listening to Evan Kleinman's talk with Cindy Mushet about flour on the Good Food show this past week, we were left thinking about bleached and unbleached flour. Mushet is insistent that unbleached flour is best, and that made us wonder why it started getting bleached in the first place...

 
 

Fresh flour straight from the mill isn't actually quite ready to be used in baking and actually improves with a little aging. Harold McGee of On Food and Cookign explains that during the aging time, flour undergoes a chemical process where oxygen in the air reacts with the glutenin proteins (which eventually work to form gluten) to form even longer chains of gluten. This means that doughs made with aged flour will have more elasticity and structure.

Fresh flour is also slightly yellowish to start off with, but then becomes paler as pigments in the flour oxidize during aging. The color change doesn't affect anything chemically within the flour, but was originally an indicator that the flour had been aged for a certain period.

Around the beginning of the 20th century, it became common to use certain chemicals to speed up the aging process, allowing milling facilities to produce more flour and save on storage space. Potassium bromate was commonly used to speed aging, and then bleaches like benzoil peroxide and chlorine dioxide were used to approximate the whiteness of naturally aged flour.

In more recent history, medical concerns have risen over the consumption of potassium bromate, so it has been mostly replaced with ascorbic acid. Although bleaching hasn't been raised into question medically, it does seem to affect the structure and flavor of the flour itself. As Cindy Mushet explained in her interview on Good Food, this makes bleached flour generally less ideal in her opinion.

What do you think - does bleached or unbleached flour make a difference to you?

Related: Good Cure Question: What Are Processed Foods?

(Image: Flickr member rjw1 licensed under Creative Commons)

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Food Science, Health, Baking Products, Ingredients - Pantry, flour, Evan Kleinman, Good Food, bleached flour, bromated flour

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Comments (5)

Is all cake flour bleached? I don't use it because I haven't been able to find it unbleached. So obviously, I'm pretty much anti-bleached flour. :)

I think I remember something about adding cornstarch to all purpose flour to approximate cake flour, but I can't remember where.

Great info about flour milling--thanks!

posted by sjbreeze on April 7th 2009 at 2:09pm
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I've used both and never noticed a difference. I buy un-bleached now in hopes that it's a little "greener".

posted by Tiamat_the_Red on April 7th 2009 at 2:41pm
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i wonder if you might be able to sub out pastry flour which is available unbleached and has a similar protein content.

Note this old question...

http://www.thekitchn.com/thekitchn/good-questions/good-question-pastry-flour-vs-cake-flour-008151

posted by sally599 on April 7th 2009 at 3:05pm
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I discovered long ago that unbleached flours simply taste better than the standard bleached flours (e.g., King Arthur vs. Gold Medal). Maybe this is due to unbleached-flour millers (usually smaller companies) sourcing higher-quality ingredients than the bigger guys, or something like that. All I know is unbleached flour has a much nicer flavor. As a blogging breadmaker (http://www.abreadaday.com), it's important to me! (Apologies for the shameless plug.)

posted by eprewitt on April 9th 2009 at 2:54pm
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posted by Scott T. on June 22nd 2009 at 5:06pm
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