Why Does my Meringue Shrink?
The science of making foams in baking (egg foams to be exact) is a phenomenon of breaking protein strands (in the egg whites) and thus lengthening them as they are beaten. This is called denaturing the proteins. Basically they stretch and lengthen and in this process they trap air bubbles. The size and strength of the bubbles determine the durability of the meringue.
An acid such as cream of tartar, makes egg-white bubbles stronger. Another way to be sure you are helping to strengthen those bubbles rather than work against them, is to gradually beat in the sugar. You have heard me say this time and again when we are beating foams. SLOWLY add the sugar. You never want to dump a heavy mass on top of a light foamy aeration that you are working so hard to achieve.
Once again in baking TIMING is everything!
If the sugar is not added before a medium foam is established, the whites get too stretchy to make a stiff foam.
On the other hand, if you add the sugar too fast, the granules won’t dissolve and the bubbles will be uneven.
Finally, if you overbeat the whites, the bubbles are stretched to their maximum so that when heated, the air pockets explode and drain liquid.
Please note that even the best made meringues have a small window of glory.
By baking the meringue as the final step, the meringue will set and get firmer.
As the meringue cools, the air in the bubbles contracts and causes slight shrinkage THIS IS NORMAL.