Few things are as disappointing, or as frustrating, to a home baker as a meringue pie topping that weeps and puddles, and few kitchen conundrums have inspired as much theorizing and contradictory advice in the pages of cookbooks. In truth, undissolved sugar in the meringue, though often blamed, has little to do with this sad condition, and humid weather, another common suspect, has even less. The real culprit is egg white, with its characteristic sensitivity to heat. Most recipes direct you to spread the meringue over a cool or lukewarm filling and then brown the topping in a moderate oven for up to 20 minutes. The problem with this procedure is that it leaves the egg white nearly raw along the bottom, where it meets the tepid filling, but scorching hot on top, where it is exposed to the ovenΓÇÖs heat. The undercooked part of the meringue simply melts as the pie stands, resulting in that infamous slippery puddle between filling and topping. Meanwhile, the overheated meringue on the surface breaks down and curdles, just like an overcooked custard, whereupon it weeps those unsightly little beads of sticky syrup.
The melting of the meringue along the bottom is easily prevented by simply having the filling hot, not warm, when you apply the meringue, so that the bottom of the meringue cooks on the heat released by the filling. If the filling has cooled before you are ready to apply the meringue, slip the pie into the oven for 5 minutes before you top it. Ideally, you will think to do this before you have finished preparing the meringue, because meringue does not like to sit once it is ready.
The overheating of the surface of the meringue and the resulting beading is a more complex problem. Heating meringue over hot water, as one does in the making of a Swiss meringue or seven-minute frosting, serves to stabilize it and make it less prone to weeping. However, heated meringue tastes dry and sticky and tends to develop a leathery skin when further baked. A better solution, we think, is to stabilize the meringue with a cooked cornstarch paste, as indicated for Soft Meringue Topping I. Of course, the making of the paste entails an extra step that you may not have time to dispatch. So if you can live with a few beads, by all means use Soft Meringue Topping II, which is made in the conventional manner.
When applying a meringue to a pie or pudding, it is important to spread a band of topping around the edge of the crust or dish before you fill in the center. If you cover the center first, you are likely to displace some of the filling and cause it to spill over. Be especially careful to heed this advice when spreading meringue over a partially cooked and still liquid filling, as in the making of chess or Key lime pie. Pie meringue must be brought to the edge of the crust at all points or else it will shrink back. When applying a meringue to a crustless pudding, spread the topping to the edge of the dish. This may not prevent shrinking, especially if the dish is greased, but at least you tried.
Meringue Safety: If you wish to be certain that any possible pathogens in the egg whites have been killed, you must heat the meringue to 160┬░F. Follow the recipe as written, being sure that your pie filling is piping hot when you spread on the topping. After 20 minutes baking, carefully insert an instant-read thermometer sideways into the center of the meringue. If the temperature is shy of the mark, bake the meringue a little longer. Be careful, though, not to go much beyond 165┬░F, or the meringue will begin to break down even if stabilized by cornstarch.
