Rethinking pie meringue
Rethinking pie meringue
The quest for stable meringue that's doesn't weep and isn't too sweet
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Magical Meringue
Of all the processes in baking, whipping up meringue ranks among my favorites. Watching egg whites and sugar transform from clear and “gloppy” to shiny and billowy feels like magic. Meringue can shine on its own in a pavlova or simple kisses or form the basis of a more elaborate bake such as macarons or souffle. Today I’m exploring a specific meringue use that has occupied my mind to what some might call an obsessive degree: pie topping.
One of my ongoing personal projects has been to develop a stable and less-sweet pie meringue. I LOVE a mile high look but too often the end product is either way too unstable (weeping and disintegration after a couple hours) or way too sweet.
I’m so pleased that I’ve finally found what I call my Goldilocks meringue. It holds beautifully for several days without weeping; and it’s gently sweet, the perfect counterpoint to a tart lemon filling / rich chocolate custard / <insert pie of choice>.
Before diving straight into the recipe, let’s discuss meringue and WHY certain problems happen. Meringue is honestly a vast subject and I’ve tried to be succinct here. But it’s very fascinating and I’ve included some sources in the footnotes if you want to dig in further on your own.
Ready? Let’s go!
Meringue 101
Meringue is essentially a sweetened egg-white foam. Sugar and egg whites — that’s it. Although one may add additional ingredients such as acid and flavorings, the only truly essential components are sugar and egg whites. The stability of a meringue will largely depend on the ratio of sugar to egg whites and the way they are combined.
Egg Whites
On their own, egg whites — which are ~10% protein and 90% water — can be beaten into a foam. When you beat egg whites, air forces some of the proteins to unwind and breaks the bonds holding them together. These unwound (or denatured) proteins can now join up with different proteins and form reinforcement around each air bubble.1 However, without any additional preservative measures, a raw egg white foam won’t last long. The water will seep out and you’ll be left with a puddle.
Sugar: Sweetness and Stabilization
We know that sugar sweetens meringue. But it also plays a huge role in stabilization. Sugar is hygroscopic — it loves water. When added to egg whites, sugar draws the water away from the protein bonds and dissolves, creating a viscous syrup. This syrup prevents seepage by greatly slowing drainage from the foam’s air bubble walls.2 It also prevents deflation by making it harder for the air bubbles to merge together and escape.3
Sugar also helps baked meringues crisp up in the oven — by drawing the water out of the egg whites, it allows more water to evaporate once the meringue hits a certain temperature. More sugar = more water bound up = more evaporation = crisper meringue. This is why, for certain applications like pavlova or crisp meringue kisses, you need a fairly high ratio of sugar to egg whites4 — traditionally 2 parts sugar to 1 part egg whites.
The good news is that with pie meringue, we are dealing with a soft (unbaked, in my case) meringue. Since we don’t need sugar to help with crispness, we can afford to use a lower ratio of sugar to egg whites and — with a couple of other tricks — still walk away with a tasty and stable end product. Huzzah!
Heat
If you want to preserve your meringue for any length of time, you must apply heat at some point. Heat both inflates the bubbles in the foam and sets (“coagulates“) certain proteins. The three common styles of meringue preparation — French, Italian, and Swiss — differ in how/when heat is applied.
In French meringue, egg whites are whipped and sugar is slowly added as the whites reach their maximum volume. At this point the egg whites are still raw, so the meringue must be baked to both set the meringue and make it safe to eat. Historically, French meringue is the style used for pie meringue. However, it is the most fragile of the meringue styles; and frankly the common pie meringue problems disappear by simply switching to a more stable preparation.
Italian meringue is created by adding a hot sugar syrup into into whipping egg whites. Italian is considered the most stable of the meringue styles because of the viscosity of the syrup and its ability to coagulate certain proteins. However, this hot syrup doesn’t technically cook the meringue, because the egg whites don’t get hot enough to pasteurize (which happens around 160F). While Italian meringue often used as a stable pie topper, particularly in professional settings, I personally prefer to use something fully cooked for health safety reasons (a lot of my desserts are consumed by very young and elderly people).
Which brings us to…Swiss! In Swiss meringue, egg whites and sugar are combined prior to whipping, then heated over a double-boiler to fully dissolve the sugar and pasteurize the whites if desired. Then it is whipped until stiff. While off the bat Swiss isn’t quite as light as French or as stable as Italian, I think in the case of pie meringue its benefits outweigh the drawbacks. Plus, we can use other tools to improve texture and stability.
The problems with traditional pie meringue
Historically, soft American-style pie meringues were made using the French method. They also contained a lot less sugar (about equal parts sugar and egg whites) than the 2:1 sugar:egg whites ratio more commonly used today. These pies were baked after applying the meringue to set the foam and make it safe to eat. These pies also used a minuscule amount of meringue by today’s standards — 2 egg whites’ worth, which is about half to a third the amount in most modern recipes.
Honestly, when you’re using such a small amount of meringue, this low-sugar baked French meringue probably works fine. The thin layer of meringue can completely bake through in the oven in a reasonable amount of time.
Problem: Weeping
However, if you want a more substantial meringue layer, you’re going to run into problems using the French method. The main one is WEEPING — that sad, unappetizing layer of liquid that forms between your disintegrating meringue and the pie filling, causing your meringue to slip off completely and bakers to cry.
Weeping is caused by undercooking. When you pile on a thick layer of raw meringue and put it in the oven, it takes a surprisingly long time to actually cook it all the way through. If the entire meringue doesn’t get hot enough, it’s only a matter of time (usually a few hours) before it begins to weep.
Thankfully, the solution to weeping is simple: used a “cooked” meringue, aka either Swiss or Italian. This way you can avoid baking the meringue altogether.
A note on condensation: What if, despite using a cooked meringue, you still encounter liquid between the meringue and filling? I think in most cases, this is due to condensation. This can occur when your meringue and filling are very different temperatures, or if you put a pie that’s still warm into the fridge. Also, some fillings are just more prone to forming a film of liquid on top (it could be from overcooking, or just the difference in humidity between the fridge and the filling). It’s not that you’ve necessarily done anything wrong — it’s just the nature of the beast. The best solution I’ve found is to sprinkle a thin layer of bread/cake/cookie crumbs over the filling before adding the meringue. The crumbs will absorb any liquid and create a dry seal. Also, I like to add my meringue to a room-temperature pie to avoid any condensation due to major temperature differences.
Problem: Overly sweet
So you’ve switched over to a cooked meringue. Your weeping problem is solved, hooray! But my other main problem for a long time was that meringue toppings were just too sweet. ESPECIALLY if you’re going the mile-high route. The meringue would look beautiful and impressive, but I would end up leaving most of it on my plate because it was just overkill. In my mind, that is a fail. Yes, aesthetics are important. But desserts are meant to be eaten, not just admired.
The obvious and most practical solution is to just use less meringue. I think the historical amount of 2-egg white meringue made with a 2:1 sugar:egg whites ratio is probably delicious and not overly sweet, especially if paired with a tart or rich filling.
But what if you just want it ALL? I’ll admit it — I love the mile-high, diner-style, swoopy meringue look! It’s fabulous and fun! So, I just started cutting the sugar in the meringue. I tried a few different ratios, settling on 1.3:1 sugar:egg whites for a good balance of sweetness and texture. (I found lower levels of sugar a bit too foamy and light for my tastes.)5
So the sweetness level was sorted. But cutting sugar doesn’t just cut sweetness — it also affects stability, even in a cooked meringue. If you know you’ll finish your whole pie on the day you assemble it, this isn’t a big issue — a less-sweet Swiss meringue should last several hours in the fridge. But if you think you’ll have leftovers beyond 24 hours, it’s wise to help your meringue out with some extra stabilizers.
A note on expectations: In the end, even with stabilizers, we’re still dealing with perishable products. Your meringue pie will always taste the best the day it’s made (eventually your filling and crust will start suffering too), and I don’t think it’s reasonable to expect that this type of baked good will remain exactly the same for a truly extended period of time. My goal was to make something that would be enjoyable and reasonably presentable for 3-4 days, the time it takes my family to finish a full pie!
The solution!
Acid, Starch, and Gelatin: Stabilization Triple Threat
Besides sugar, there are several other tools that can help in meringue stabilization. I employ three of them in my less-sweet pie meringue: acid, starch, and gelatin.
Acid: Adding acid (typically cream of tartar, but can also be vinegar or lemon juice) lowers the pH of the egg whites. This environment helps proteins unfold more quickly, which then reinforces the air bubbles faster to create a more stable foam. I always like adding an acid to my meringues not only as an insurance, but also as a flavoring agent.
Starch: I first learned of adding starch to a soft pie meringue from one of my favorite baking resources, Shirley Corriher’s brilliant Bakewise. Adding starch to soft pie meringue helps prevent shrinkage and creates a tender, easily sliceable meringue. I opt for Corriher’s method of adding a pre-cooked cornstarch slurry to my finished meringue. I also think that the added water from the slurry makes for a lighter, softer meringue which is particularly fun to eat. For that reason alone, I’ll always add the cornstarch slurry to my pie meringue.
Gelatin: As a final insurance policy, I like to add a small amount of gelatin to pie meringue. Gelatin’s job is to gel in the presence of moisture; so in the case of meringue it binds up any remaining free water and essentially sets the foam. The trick is to use a small amount that doesn’t set the meringue too firmly. We’re not making marshmallows— you want to be able to cut through it easily with a fork. I go with about 1% of the weight of the egg whites and sugar pre-cooking/whipping. The meringue with added gelatin will be a little stiffer after sitting in the fridge overnight compared to freshly made, but it’s still pleasant to eat. If you know for sure that you’ll be consuming your meringue-topped pie on the day it’s made, you can skip the gelatin. But if you think you’ll have leftovers beyond 24 hours after assembly, it’s worth adding.
Mile-High Goldilocks Meringue
Makes enough for one mile-high meringue to top a 9” pie
Ingredients:
For the cornstarch slurry
7g (1 Tbsp) cornstarch
65g water
For the gelatin
24g cold water
4g (1 1/4 tsp) powdered gelatin
For the Swiss meringue
170g (about 6 large) egg whites
220g granulated sugar
1/4 tsp kosher salt
1/4 tsp cream of tartar
1 tsp vanilla extract
Method:
Make the cornstarch slurry: In a small saucepan, whisk together the cornstarch and water. Cook over medium heat, whisking frequently, until the mixture thickens and turns translucent. Measure out 45g of the slurry and discard the rest (it’s hard to make a smaller amount of this! Sorry!). Set aside to cool while you continue on.
Bloom the gelatin: Pour the cold water into a small bowl. Sprinkle the gelatin evenly over the surface. Allow to bloom while you make the meringue.
Make the meringue: Fill a saucepan with a couple inches of water and bring it to a simmer. Combine the egg whites, sugar, salt, and cream of tartar in the bowl of a stand mixer and whisk to combine. Place the bowl on top of the saucepan to create a double-boiler — this heats the egg mixture gently to avoid scrambling the eggs. The base of the bowl should not touch the simmering water.
Heat the egg white mixture, stirring frequently and scraping the sides and bottom of the bowl with a heatproof spatula, until it reaches 161-165F on an instant-read thermometer. The mixture should be quite thick and foamy and the sugar completely dissolved.
Turn off the heat and add the bloomed gelatin to the egg white mixture. Stir until dissolved.
Remove the bowl from the double-boiler and transfer to a stand mixer fitted with the whisk attachment. Whisk on high until the meringue is bright white, shiny, and holds a medium peak, about 6-8 minutes. (Note: If you’re used to a higher-sugar meringue, this one isn’t quite as stiff but it should still hold peaks and keep its shape well on a pie.) Beat in the cornstarch mixture a third at a time, followed by the vanilla. Pile on prepared pie immediately, using the back of a spoon or spatula to make decorative swirls as desired. Refrigerate as needed for your filling to set. Toast with a blowtorch before eating, if desired.
Corriher, Shirley. Bakewise. New York: Scribner, 2008.
McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribner, 2004.
See Nicola Lamb’s
newsletter on Pavlova for a detailed look at how the ratio of sugar:egg whites affects baked meringue.To further cut down on sweetness and for extra flavor, I love to use toasted sugar — a brilliant discovery by Stella Parks — in almost all my meringue preparations. For more information, see https://www.seriouseats.com/dry-toasted-sugar-granulated-caramel-recipe.