I've been baking French-style bread loaves (not baguettes) for years. The ingredients are flour, salt, water, yeast, and about one tbsp cornstarch per cup of flour. For the last year or so, the inside of the loaves has sometimes been gray rather than white, but with little or no change in the taste. I have not changed ingredients nor preparation technique. Flour has been King Arthur bread flour for years. I am at a loss to explain the change.

I'm in Atlanta, about 1,000 feet above sea level. Earlier this summer, I made bread every day for two weeks at a beach house party, using equipment and ingredients brought from home. Every loaf turned out perfect, with no hint of gray. I have no idea why that might make a difference. (There's an electric oven at the beach, gas at home, but I made perfect, or at least white, bread with the gas oven for many years before this problem started.)

Also, if I cut into a loaf right after it comes from the oven, it's always white. The graying process seems to happen over a couple of hours. (I bake in the afternoon for an evening dinner.)

Edited October 5 to add: Additional data points: I've bought a three-loaf baguette pan with perforated bottom and I've been using it for about a month. No gray bread. I've introduced three new variables:

  • Three loaves of about 260 g unbaked weight instead of two at 390-400 g unbaked.
  • The pan is non-stick aluminum instead of black steel.
  • The pan that produced the gray loaves was not perforated.

Ingredients and preparation, except for forming three loaves, are exactly the same. I'm not sure whether I've learned anything or simply confused matters even further.

  • 1
    When all things are the same, I tend to look at water quality. I typically bake sourdough though. I've had my starter turn gray due to exposure to air and alcohol buildup, and I've noticed a gray hue in the finished product when I experimented with long cold bulk fermentation (24 hrs +), though neither of these reasons seem to fit your question, unless you're making sourdough. – Michael E. Aug 23 '14 at 4:02
  • Not sourdough; dough made and baked the same day. I'm using city water that probably has very little variation, but I'm not sure how I would test that. – Bob Brown Aug 23 '14 at 4:12

What kind of salt are you using?

In the presence of iodine, starch can turn a surprisingly purplish-black color. This phenomenon has be leveraged for many decades in medical examiners' offices, to help determine the contents of a last meal in a cadaver (pardon the unappetizing digression).

Iodine is an essential nutrient, vital for the proper functioning of our thyroid (read more about Iodine Deficiency) that has relatively few ways of entering our bodies through our diet other than through shellfish, meats, eggs, and some dairy products.

One way to combat the problems of iodine deficiency is its addition to our salt, which we consume in predictable quantities and never goes bad. Table salt contains up to 25mg/kg of iodine and that number has been on the rise since its safety and helpfulness have been demonstrated repeatedly. Sea salt contains some iodine, as it is naturally occurring in the ocean, but in a much smaller quantity.

Maybe when you were at the beach, your salt supply changed to sea salt or an uniodized version and and when you returned and used the regular Iodized Morton's or Iodized sea salt.

  • Interesting notion, but can the discoloration be caused at such low concentrations? – logophobe Sep 24 '14 at 17:59
  • In Europe, iodinized table salt is the norm, not the exception. And yet I haven't seen bread turn grey. So it is a very interesting idea, but the evidence is against it. – rumtscho Sep 24 '14 at 18:11
  • @rumtscho As I mentioned in the post, the concentration of Iodine in table salt has risen dramatically in the past century. Iodized salt in some places (Switzerland, in the wikipedia article) contains more than 7x more iodine today than in the 1950s. Maybe the OP makes really salty bread? – speedfranklin Sep 24 '14 at 19:27
  • @speedfranklin I am talking about breads today, not breads in the 1950s :) I doubt that the OP can make really salty bread and not get other problems (besides a terrible taste, too high a salt concentration will also kill the yeast, and probably interact with gluten formation too). But I have also made salt-dough with iodized salt, that's like modeling mass, about equal amounts of salt and flour, and it doesn't turn grey. – rumtscho Sep 24 '14 at 19:44
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    @speedfranklin: Son of a gun! I've been using one tsp of Morton (U.S.) iodized salt with three cups of flour. At the beach, I used whatever was in the pantry, which might not have been iodized. I'll have to perform an experiment. Unhappily, I can't do it soon. – Bob Brown Sep 25 '14 at 1:14

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