EnerG and Bob's Red Mill are the common commercial egg replacers available in US. They are egg free, made with plant/vegetable based starch and leaveners. This is also available in health food stores (Whole Foods) and in the organic aisle of some of the regular supermarkets.
I have used only EnerG so far and have had good results. EnerG does not work well in all recipes and especially with some of the boxed mixes. Trial and error method is the way to go.
The EnerG box comes with the instructions to use the product, which is blending 1 and 1/2 teaspoons of the powder and 2 tablespoons of warm water until it is frothy. Some cookbook authors suggest using twice or thrice the amount of powder. I have also noticed that the mixture reduces in volume after a while, so you would have to add about 1-2 tablespoons of extra water depending upon the consistency of the dough.
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recipes using EnerG and Bob's Red Mill egg replacer as an egg substitute.