Effect of adding whole egg or yolk to filo pastry? I had some success making filo pastry for apple strudel with a mixture consisting of flour, olive oil, lemon juice and white vinegar. The result was actually quite nice except the pastry was very delicate. I made the dough very thin using a pasta machine. I am wondering what would happen to the pastry if I used an egg. I am thinking it might be more crunchy... due to the egg introducing more protein fibers. What do you think?
In my personal experience, adding eggs to dough makes it softer, not crunchier. Adding an egg makes it an &quot;enriched dough&quot; that has the ability to hold onto moisture despite being baked.
Many apple strudel dough recipes include an egg or two in the dough, so you should just go for it.
Finally, while strudel dough is very similar to filo, it is not the same thing, which may be causing some confusion for you.  Per one baking blog:

So the difference is simple, it's the fat! In the Puff Pastry the butter is folded in, in the Strudel dough the oil is part of the dough from the beginning and the Phyllo dough is brushed with oil before being baked.

So per your question, strudel dough sometimes includes an egg, whereas filo (phyllo) never does.