Q: When frying a pastry packet, why should I seal dough edges together with egg white instead of water?
A: Egg white is pure protein and cooks immediately when exposed to the high heat of the frying oil. Whereas water would immediately steam in the hot oil and push the dough edges apart instead of sealing them together, egg white is a perfect sealant and will not splatter in the hot oil or denature the oil with moisture the way water would react.
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