I've found that with muffins and most other quick breads my favorite substitute for an egg is:
- Two heaping tablespoons of applesauce and one additional teaspoon of baking powder added to the dry ingredients.
It will work well with one to two eggs. It often works for three eggs, but the results start to become a little less predictable when you substitute that many. I wouldn't try it with four eggs, however you will rarely come across a muffin or quick bread that calls for more than three eggs anyway. If you have to double a recipe, try making the second batch in another bowl to keep the quantity of eggs per batch to three or less.
Why is it my favorite? Applesauce and baking powder are easy to find and inexpensive. The applesauce makes the muffins moist and binds the ingredients together. The extra baking powder gives the muffins a little leavening or in other words, helps the muffins to rise without the egg.
In some cases you don't need the extra baking powder, or you can cut the baking powder down to a half teaspoon per egg, but this depends on the recipe. Too much baking powder can leave an undesirable taste in your baked goods. Not enough leavening can cause the baked good to fall, or be too dense and wet.
If it's a muffin recipe with one egg, give this a try. Tell me how it works for you. It is my favorite for basic muffin recipes.
Here are a couple of recipes I altered and were a hit at our home:
Blueberry Muffins (egg and diary free)
Bran Muffins (egg and dairy free)
One more hint. If you use whole wheat flour (I often use half whole wheat flour), you may need to add additional liquid to your recipe (try somewhere between 2 TBS to 1/4 cup to start). It seems to soak up more liquid than all-purpose flour.
Good luck!

