The surface of pastry dough turning grey when stored in the fridge is not uncommon—I have experienced it many times and have tried to figure out what is happening.
This blog post explores why pastry undergoes this color change, whether it is harmful, and how to prevent it from happening.
The color changes to gray in pastries, occurring when exposed to air, are most often caused by the oxidation of ingredients such as flour, eggs, baking powder, fruit, and vegetables. Although this color change doesn't affect the quality of the dough, it does impact its appearance.
Causes of Pastry Dough Turning Grey
Wheat flour naturally contains both enzymes and free fatty acids that react in the presence of oxygen, causing the dough to turn gray. The oxidized free fatty acids, in turn, interact with and “bleach” the carotenoids naturally present in wheat flour. This bleaching effect renders the dough translucent and gives a greyish color to its appearance.
The high iron content in the egg yolk may also cause the outer greenish-gray color of the dough. This color change occurs when the dough is refrigerated for over 18 hours without cooking.
Baking powder that contains aluminum can potentially cause grey discoloration in the dough. To minimize the risk of grey discoloration in your dough, you can consider choosing baking powder labeled aluminum-free.
Using aluminum utensils can also cause grey discoloration on pastry dough, as I experienced when shaping spritz cookies with an aluminum pastry extruder. The reaction is a result of the interaction between the naturally occurring compounds in the dough, particularly the free fatty acids, and the aluminum.
Fruit- or vegetable-based pastry fillings may contain pigments sensitive to oxygen and can undergo changes in color, such as melanin in apples.
Anthocyanins, which are responsible for red, purple, or blue colors in plants, can be easily discolored due to various factors such as temperature and light. Potatoes contain starches, that oxidize when exposed to air.
Preventing Dough Discoloration
To prevent undesirable color changes in pastries due to oxidation, it’s essential to minimize exposure to air. This includes airtight storage, and, when possible, adding antioxidants such as vinegar to recipes to slow down the oxidation process, as suggested by King Arthur Baking.
When refrigerating, wrap the pastry dough well to minimize its exposure to air. While refrigeration slows down oxidation, moisture in the fridge can also contribute to the oxidation process. You can keep the pastry for up to two days in plastic wrap or an airtight container.
Additionally, freezing can help preserve the quality and color of the dough for an extended period. Explore more information related to food safety in our article on the benefits of food preservation.
When Should You Discard Pastry Dough?
While some discoloration on the surface of pastry dough, like a slight greying, might be caused by oxidation and can be safe, significant changes, such as an unusual sliminess, stickiness, or drastic color changes, can signal spoilage.
One of the primary indicators of spoiled pastry dough is an unusual or off-putting odor. If the dough emits a sour, rancid, and unpleasant smell, it suggests that harmful microbial activity may have taken place.
If you observe any patches of discoloration on the surface of the dough that are visible signs of moldy growth, it’s a clear indication that the dough is no longer safe to use.
Final Thoughts
In conclusion, the grey discoloration of pastry dough occurs due to the oxidation of various ingredients, such as flour and eggs. Proper storage techniques, including airtight wrapping and freezing, can help preserve the dough’s color.
While slight greying due to oxidation is considered safe, any drastic changes in texture, smell, or the presence of mold should be treated as signals to discard the dough.
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