I am going to be baking a pumpkin pie for Thanksgiving but me as well as several family members are currently losing weight together... I'm already replacing the sugar with stevia to dramatically drop the calorie count. BUT, the recipe calls for 4 eggs and I was wondering if I could further reduce the calories by using only egg whites instead... would this ruin the flavor of the pie? I've replaced whole eggs before when baking brownies and they came out fine, but I just want to make sure it won't severely mess up the Thanksgiving classic :)
Pumpkin pie is basically a custard, removing the yolks could change the texture of the pie. Yolks contribute both proteins and fats to the pie which are important for the structure of the filling as well as its creaminess/smoothness. In general, two whites can be used to replace one whole egg. Avoid whipping or over-mixing the filling to prevent making the custard rubbery.Be sure not to overcook the pie, without the yolks there to emulsify the filling and lubricate the protein bundles, you could end up with a dry, curdled mess.
Yes, you can, but it will reduce the tenderness of the custard. It will be slightly stiffer and slightly less... erm... creamy or pudding like.
Egg whites are essentially water and protein (albumen) and set up to a more resilient and slightly rubbery texture than do egg yolks which contain significant amounts of fat and natural lecithin, which is an emulsifier.
This is why the tenderest, smoothest custards are made with only yolks, and no whites. Using whole eggs is a compromise between the two textures.
Of course, the pumpkin pie filling also has significant amounts of starch, pectin, and general pumpkin solids, so you may not notice the difference (especially if you won't be comparing two pies side by side made with different parts of the egg).