Theories abound on why yeast breads that contain walnuts (or pecans) turn purple. After reading a paper in the Journal of Agricultural and Food Chemistry, we decided to pursue the one that seemed most plausible: that the iron in flour is reacting with gallic acid found in walnut skins to create a color change.
To confirm this theory, we combined walnuts, water, and (to minimize variables) crushed-up iron supplements from the vitamin aisle and watched the water immediately turn a deep purple. We repeated the experiment with pecans, which were equally reactive, and almonds and hazelnuts, both of which triggered a slightly less dramatic color change.
So why don’t all baked goods containing these nuts turn purple? The answer has to do with acidity and time. The purple tint appears only in an acidic environment, and most baked goods aren’t acidic enough to cause the reaction. But thanks to the acids produced by yeast as it ferments, bread dough does have what it takes. In addition, since gallic acid leaches out slowly, rising bread dough gives time for the effect to happen.
Only tiny amounts of gallic acid are needed to bring out the purple. The tint can’t be prevented completely, but it can be minimized by blanching the walnuts in boiling water for 1 minute before using.
A reaction between gallic acid naturally found in walnuts and iron in flour results in purple discoloration. This transformation occurs in an acidic environment, which is facilitated by the acids released during the fermentation process in bread dough.
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Why do walnut breads sometimes turn purple? Can anything be done to prevent this?
Theories abound on why yeast breads that contain walnuts (or pecans) turn purple. After reading a paper in the Journal of Agricultural and Food Chemistry, we decided to pursue the one that seemed most plausible: that the iron in flour is reacting with gallic acid found in walnut skins to create a color change.
To confirm this theory, we combined walnuts, water, and (to minimize variables) crushed-up iron supplements from the vitamin aisle and watched the water immediately turn a deep purple. We repeated the experiment with pecans, which were equally reactive, and almonds and hazelnuts, both of which triggered a slightly less dramatic color change.
So why don’t all baked goods containing these nuts turn purple? The answer has to do with acidity and time. The purple tint appears only in an acidic environment, and most baked goods aren’t acidic enough to cause the reaction. But thanks to the acids produced by yeast as it ferments, bread dough does have what it takes. In addition, since gallic acid leaches out slowly, rising bread dough gives time for the effect to happen.
Only tiny amounts of gallic acid are needed to bring out the purple. The tint can’t be prevented completely, but it can be minimized by blanching the walnuts in boiling water for 1 minute before using.
What’s The Real Deal: Purple Bread
FAQ
Why does bread turn purple?
Does walnut turn purple?
What turns bread purple?
Why is walnut bread blue?
Why is my bread purple?
It’s only a cosmetic issue and, if you don’t want purple bread, it’s easy to remedy! It’s the acid in these two ingredients that bleach out the purple hue. Both are going to make any recipe slightly more acidic and also will add just a slightly sour flavor. This isn’t unpleasant and even makes bread taste more like sourdough. 1. Lactic Acid (BEST)
What are the negative health effects of Walnuts?
Although walnuts are abundant in health promoting nutrients including healthy fats, fiber, plant sterols, vitamins, and minerals, they can also have negative effects. For example, allergic reactions to walnuts can occur in those with tree nut allergies. If consumed in excess their high fiber content can cause digestive discomfort, bloating, and diarrhea. Walnuts are calorie dense and can potentially lead to weight gain if consumed regularly and in excess.
How do you make sourdough walnut bread?
A how-to guide on making a sourdough walnut bread, full of whole wheat and with a rich nutty taste from walnuts and a hint of sourness. Mix 50 grams wheat flour with 50 grams of water and 25 grams of sourdough starter. Place the levain at room temperature and let it ferment for 8 hours, or until it has at least doubled in size.
What goes well with sourdough walnut bread?
Bread and nuts almost always go well together, and this sourdough walnut bread is no exception. The hint of sourness from the bread and the rich nutty walnut taste is a perfect combo. Try it with a slice of good quality salami. But I have to warn you. You may end up devouring the whole bread.