Quality Meringues??

Firstly, sorry if I misspell meringues.

I would like to know what the quality is like of the protein in meringues. I know whenever my mom makes some cake for the family and theres beaten up eggwhite left we make some meringues, either with just a bit of sugar or some syrup/honey or sometimes sweetener (and it DOES taste good). My first question is, does the protein remain the same or is it too denatured by baking? we can usually make a huge tube from like 20 eggwhites and want to know if i can use that as an extra protein snack, or is it of no worth. Secondly I'd just like to know how long beaten up eggwhite is allright to eat for if kept in the fridge. I sometimes get addicted to eating beaten up whites with some sugar - perfect protein with little carbs and no fat.

I personally try to stay away from simple sugars and I always use my eggs as and when I need them.

I,m not sure how long they can be kept in the fridge and if it was me I would just stick them in a shake with milk and a protein powder.

Billy