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.

  • 3
    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, 2014 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, 2014 at 4:12
  • Just a couple points: Aluminum is a far better conductor of heat than is steel. Our city water varies from pH 8.2 to 6.5, with solids from 200 to 300 ppm. The pH changes alone are enough to change the solubility of various pipe deposits. Oct 15, 2019 at 0:01

2 Answers 2


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, 2014 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, 2014 at 18:11
  • 2
    @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, 2014 at 1:14
  • 1
    Could it be that the flour manufacturer used, and later discontinued, a harsh bleaching process? Jan 17, 2016 at 0:42
  • 1
    But only (elemental) iodine produces the purple color when combined with starch. Iodide or iodate, which are the forms commonly added to salt, do not. Oct 15, 2019 at 8:36

Flour... Basically flour you purchase nowadays in stores is pretty low quality. Flour can sit on a shelf a long time before you get it because not a lot of people are baking nowadays. The older it is, the poorer it performs and in my experience the greyer it is. I typically throw out all my flour if I notice it is not producing a clean white light loaf. I have used many different brands over the years with all producing gray tinted loaves at times. I also notice a wide variety of crumb types and taste. Older flour is not tasty, nor does it make good bread. The best tasting bread I have tasted came from a farm where they ground their own grain. So... In a nutshell, flour you purchase in stores is very poor in quality due to many factors. Try to find a organic mill and purchase direct. Happy baking!

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