Egg foams are one of the natural marvels of food chemistry. Simple egg whites can expand six to eight times in volume when whipped! Fascinatingly, egg whites have been used to make foams since before the Renaissance (read: before the whisk was even invented)! Our ancestors used a variety of surprising techniques to foam egg whites, including wringing egg whites through sponges, slapping the surface with very stiff dried fruit slices, and using bundles of straw as a sort of predecessor to the modern whisk. Egg foams can be incorporated into a variety of dishes, such as meringues, cakes, soufflés, sauces, mousses, and cocktails. In the coming weeks, I’ll be treating you to some awesome Valentines-friendly recipes that incorporate egg foams–a truly impressive (and romantic) ingredient!
But wait, this is confusing. Recipes vary widely when it comes to egg-foam advice, and they often make it seem like any little detail could make or break your recipe. You may find yourself asking: Why would I want to use eggs that are a few weeks old? Do I really need to wait until my eggs come to room temperature before whipping? Does it matter what kind of bowl I use? Do I really need to use cream of tartar, or is salt an okay substitute? It says I should add sugar at the end of whipping, and then only a little at a time, but wouldn’t it just be easier to add it at the beginning? How will I know if I’ve overbeaten them, and what the heck is a stiff peak anyway???…whew! So many rules for something so simple!! I’ll break it down for you, so you can decide which “rules” you want to follow and which you want to throw out the window.
But first a little science, so we can understand why there are rules at all. All foams are a type colloidial dispersion known as a suspension, in which air is dispersed throughout a (usually) liquid phase without dissolving. The special proteins in egg whites are what allow stable foams to form. Proteins are large molecules, as molecules go. Because they’re so big, there are areas along their chain that are hydrophilic (water-loving) and areas that are hydrophobic (water-fearing). In nature, proteins fold themselves into a specific shape based on these characteristics. They keep their hydrophobic areas on the inside, where they are protected from exposure to water, and their hydrophilic areas on the outside. As I mentioned in my Why Apples Turn Brown post, when proteins are denatured, they unfold into long, shapeless chains and try to bond with the other proteins around them.
Denaturation usually happens in the kitchen because of heat or acidity, but in the case of egg whites, the physical whipping causes the proteins to unfold. Once unfolded, the proteins’ hydrophobic and hydrophilic sides are exposed to the water-rich fluid around them. As you might imagine, this is no problem for the hydrophilic side of the chain, but the hydrophobic side will search for any escape…for instance, in an air bubble!
So as your whisk denatures these proteins and simultaneously introduces air bubbles, the unfolded proteins congregate on the surface of each bubble, with their hydrophilic side remaining happily in the egg white liquid, while the hydrophobic side protrudes into the bubble to escape all that terrible water. Meanwhile, the proteins are forming bonds with each other around the surface of the bubble, thereby creating a strong and stable network of protein that keeps the air trapped and dispersed throughout the fluid egg. COOL!
Here are the top ten “rules” for making egg foam. Some I debunk, some I validate. Take a look at my results, and you’ll never shy away from another soufflé, mousse, or meringue recipe again!
Top Ten Rules for Egg Foams:
1. Room-temp v Cold egg whites.
Why. Warmer temperatures lower the surface tension of liquid egg whites, thereby making it easier for bubbles to form. Cold eggs are also easier to separate and run a lower risk of the yolk breaking and leaching destructive fat into your egg whites (see number 8 below).
Is it for real? Many recipes make this rule sound like it’s do-or-die, but I’ve used cold egg whites plenty of times, and I find they warm up pretty quickly once I start whipping, particularly if it’s only one or two egg whites.
The proof. Below is a picture of an egg white that was whipped straight from the fridge and one that was allowed to come to room temperature. Can you tell the difference? Me neither.
The bottom line. So in short, sure, use room temp egg whites if you can, but if you don’t have time to let your egg warm up, it’s not the end of the world. In fact, you may not see any difference at all. And if you’re still worried about it, try placing your hand against the bottom of the bowl as you whip. The heat from your hand will encourage the cold egg to warm up a bit as you work it. Voila!
2. Old v Fresh eggs.
Why. Old eggs are often recommended because their egg whites have thinned out over time, which makes them easier to whip.
Is it for real? It’s true; older eggs whip up faster.
The proof. When beaten for the same amount of time, the fresh egg (left photo) reached stiff peaks, but nowhere near as stiff as the old egg on the right. The expiration dates for these two eggs were about 3 weeks apart.
The bottom line. Although the older egg whipped up more quickly, they both were able to reach stiff peaks and roughly the same volume. So there would be no noticeable difference in your end product. It really comes down to how long you’re willing to wait for the stiff peaks. With the fresh egg, it seems to get frothy just as fast, I found the transition from soft to stiff to extra stiff to be the sluggish part. If you’re whipping by hand and you need stiff peaks, it might be worth shopping around for the oldest eggs you can find. If not, then just use your electric beater and know it may take a little longer. Hey, that might be a good thing if you’re a chronic overbeater like I used to be (before I learned about number 10)!
A health-related side note. Although I did just endorse using old eggs, if you’re planning to consume your egg white foam raw (uncooked), as is often the case with mousses and cocktails, always used the freshest eggs possible and WASH the outside of the egg before cracking to reduce your risk of salmonella exposure! (Just know that even with the freshest eggs, there is no way to completely eliminate the risk from salmonella in raw eggs and poultry products.) Please also remember that the very young, very old, ill, pregnant, and immuno-compromised are more susceptible to food-borne illness than the average healthy adult. If you’re not comfortable consuming raw eggs, there are a variety of pasteurized egg products available on the market that can serve as a substitute, although whipping characteristics can be different (see number 8).
3. Copper v Plastic v Other (glass or stainless) bowl.
Why. Copper bowls are recommended for a variety of reasons. Firstly, it’s traditional. They were popular for whipping egg whites even as early as the bundle-of-straw whipping days! Copper prevents overbeating by preventing strong sulfur-sulfur bonds from forming between proteins. The downside is that it introduces extra copper into your food, which some experts think could pose a health risk. Copper bowls are also expensive and difficult to keep clean.
Plastic bowls are not recommended because they have porous surfaces that can trap fat particles even after washing. That’s bad because fat destroys egg foams (see number 8).
Is it for real? Yes; an untarnished copper bowl will prevent overbeating, but these days there’s a better, cheaper, and safer way to block the same sulfur-sulfur bonds, and that’s cream of tartar (see number 4).
Yes; plastic bowls can trap fat particles, but will that really hurt your foam?
The bottom line. The best option is to use a glass or stainless steel bowl along with a dash of cream of tartar to prevent overbeating. It’s what most people use, and it’s completely safe and reliable with no risks to your health or foam.
If you have a beloved copper bowl you want to use anyway, you’re not realistically going to overdose on copper from occasional use. Those that oppose copper bowls on a nutritional basis are taking the safest possible stance. I recommend that route as well (why take the risk?), especially if children will be consuming the foam.
If a plastic bowl is all you have, then it’s doubtful your egg foam is going to draw out fats that even a thorough washing was unable to remove. Go ahead and use plastic if you need to; chances are, you’ll come out just fine. You will need to add cream of tartar to prevent overbeating.
4. Cream of tartar v Salt.
Why. Cream of tartar (a source of tartaric acid) is added to egg whites to prevent overbeating. It works by decreasing the pH of the egg foam and preventing the formation of sulfur-sulfur bonds between proteins, which are responsible for the crumbly, leaky texture of overbeaten foams. Acids, like cream of tartar, flood the egg with excess hydrogens. When a sulfur becomes available for bonding, it’s much more likely to find a harmless hydrogen to bond with than another sulfur. This allows egg whites to be beaten for much longer without overbeating.
Salt is commonly recommended as a substitute when cream of tartar is unavailable.
Is it for real? Yes; cream of tartar is very effective against overbeating, and it’s relatively flavorless. An 1/8 of a teaspoon per egg white is the recommended amount.
Salt definitely does NOT work. In fact, salt increases whipping time and decreases foam stability by competing for bonding space along the protein, which weakens the protective protein wall around each bubble. It’s best to keep salt far away from your foam and add it to other set of ingredients if it is required for flavor in the recipe.
The proof. In the photo below, the foam on the left was whipped with cream of tartar. The foam on the right was whipped with salt. The cream of tartar foam looks fluffy and uniform, with stiff peaks and a fine texture. The salt foam is overbeaten and leaky, with a crumbly-looking texture.
The bottom line. If your recipe asks you to whip your egg whites with a pinch of salt, just know they REALLY mean to say cream of tartar instead. If you already added salt, don’t panic; your eggs will still whip, they just won’t be as happy about it. Since the salt has nothing to do with preventing overbeating, you’ll still need to add some cream of tartar.
5. Adding sugar at the start v the finish.
Why. Sugar is delicious and completely changes the texture of egg white foams. Most recipes call for adding sugar only at the end of beating, but the occasional recipe directs you add it from the start. Is it really necessary to wait?
Is it for real? Yes; it does make a difference whether you add the sugar at the start or finish of beating. Sugar can both help and hurt egg whites. Add it all at once at the beginning and it competes for water and decreases the egg white’s capacity for holding air. This leaves you with a syrupy, dense foam. Add it a tablespoon at a time toward the end of whipping and the egg whites have time to incorporate more air before any competing sugar molecules are introduced. The purpose of the slow addition is to prevent the sharp sugar crystals from popping too many bubbles before they are able to dissolve. And the really great news about sugar foams (aka meringues) is that the sugar adds structure and stability by thickening the fluid surrounding the bubbles and protecting them from breakage. In fact, it completely prevents the liquid portion of the foam from draining toward the bottom of the bowl, as will happen over time with ALL un-sugared raw egg white foams. Seriously. You can leave it out all day and night and not a drop of liquid will leach out. It’s amazing!
The proof. The egg foam on the left was beaten with sugar from the start. As you can see, it is a puddle of thick syrupy goo that can’t hold peaks of any sort. The egg foam on the right had the sugar added slowly only after reaching very soft peaks. It’s glossy and voluminous. Perfect for pies or meringue cookies!
The bottom line. Add sugar one tablespoon at a time only after reaching soft peaks. This will give you perfect, stable meringue every time. Don’t add your sugar at the beginning unless you dislike fluffy meringue toppings and you’d like to try a smooth, dense one.
6. Adding water.
Why. Adding water to your egg whites thins them out and makes them easier to beat.
Is it for real? Not really. Your foam will be lighter and softer (which sounds nice), but you’ll find it’s nearly impossible to reach stiff peaks. Maybe a soft foam is okay with you, but the added water will quickly drain from the bubble walls, leaving you with a fragile, dry foam with a watery layer at the bottom.
The proof. To the egg white below, I added a teaspoon of water, which is about as much water as you would introduce by leaving a large bowl wet after a rinse. As you can see in the right hand photo, the water drained out fairly quickly, leaving my foam layer dry and brittle.
The bottom line. Avoid adding water to your egg whites. This is why recipes often tell you to use a clean, dry bowl. Depending on how many eggs you’re whipping, a wet bowl can really have an impact. Egg white solutions that are comprised of 40% or more water will not hold a stable foam at all.
7. Soft peaks v Stiff peaks v Overbeaten.
Why. Almost every recipe involving egg white foams will require you to recognize soft peaks, stiff peaks, and an overbeaten foam. Sometimes there is a fine line between perfect peaks and overbeaten, ruined egg whites (esp if you’re not using cream of tartar). Knowing which phase your egg foam is in removes most of the confusion cooks have regarding egg foam recipes.
Is it for real? The stiffness your foam reaches, and whether or not it’s overbeaten, will almost always affect the volume and texture of your final product, so it’s important to recognize the different stages. A foam becomes stiffer as more air is whipped into the mixture. More air means the liquid phase around the bubbles’ surfaces thins out and flows less easily.
The proof. The slideshow below shows an un-sugared foam in its different phases. Note that there are a range of soft peaks and a range of stiff peaks. Unfortunately, recipes don’t usually specify what they mean, so use your best judgement and/or look around for similar recipes with photos or videos as a reference.
The slideshow below shows a sugared foam (meringue) in its different phases. Note that there are a range of soft peaks and a range of stiff peaks. Unfortunately, recipes don’t usually specify what they mean, so use your best judgement and/or look around for similar recipes with photos or videos as a reference.
The bottom line. Know your peaks. “Soft peaks” in a plain (un-sugared) egg white foam are those that can’t stand up on their own (beginning stage of soft peaks) or have chubby or curvy looking bases and tops (latter stages of soft peaks). “Stiff glossy peaks” are those that leave a sharp little peak behind. Its tip can be a little droopy (beginning stages of stiff peaks), as long as the base of the peak is firm and able to hold angular shapes. In the latter stages of stiff peaks, the peak tips will be sharp and won’t droop. Stiff peaks shouldn’t ever really be wobbly. The ‘glossy’ term refers to the fineness of texture of your bubbles. The longer you whip, the smaller the bubbles get and the smoother and more reflective the surface of the foam. It’s not going to be like a mirror or anything, but it should look fairly smooth and moist. If you’re foam looks dry, unreflective and/or gets chunky when gently stirred, you’ve probably overbeaten your foam. This happens when the egg proteins have bonded so strongly with each other that they squeeze the liquid out from between them, which results in thin, fragile bubble walls and a growing puddle of watery egg liquid at the bottom of the bowl. Ew. If you overbeat your foam, you may need to start over. It’s a good idea to check every 30 seconds or so once you start to see your whisk leave tracks in the foam. Plain eggs whites move quickly from soft peaks to overbeaten, so keep a close eye on them! Adding cream of tartar at the beginning will help prevent you from overbeating your eggs, and it really makes a world of difference (see number 4).
If you added sugar to your foam, your overall foam will be heavier, stickier, and with finer, smaller bubbles and a shinier surface, and most importantly, it will be more forgiving. Here, “stiff, glossy peaks” really means glossy! For stiff peaks, look for sculpted looking peaks that stand up straight (at least mostly) if the top curls back down or wiggles a little, that’s okay, it’s just because the foam is heavy. If the base of the peak is sturdy, you’re there! If the whole peak flops over, or doesn’t have a sturdy base, then you’re at the soft peak stage. Another consideration with sugary foams is grit. Be sure to feel your foam’s texture before calling it done. If it’s still gritty with sugar, whip a little more. If you’re worried you’ll overbeat it, don’t be. It’s almost impossible to overbeat a sugared foam. I tried, and the motor on my mixer overheated long before anything bad happened. You can get away with a little bit of grit, but large sugar particles can attract water from the air and cause little beads of ‘dew’ to form on your meringue. So keep beating until it’s gone!
8. Things that destroy egg foams.
Why. Fats and detergents (soaps) destroy foams. If there’s any fat, oil or grease residue in your bowl, your eggs will take longer to whip, won’t reach their full volume, and are less stable. Even if you get them whipped, a few drops of fat will continually work to degrade your foam. Detergents can be just as damaging. In fact, they both work to destroy egg white foams in much the same way. Fats and detergents both like to form foams (think whipped cream and bubble bath), but their desire to “get in on the action” is a little too aggressive. They compete with protein for space at the air bubbles’ surfaces. Soon, the protein-protein bonds that made a protective wall around each bubble are weakened, and the bubble pops. The fat or detergent molecules move on to find the next bubble to cozy up to…and destroy. You get the idea.
Is it for real? Yes. The most common method of fat contamination is from egg yolk. If the yolk breaks, it’s difficult to avoid getting a little of it in your egg whites. Detergents can come into play if your bowl hasn’t been rinsed well enough after washing.
The bottom line. Be careful when separating your eggs, and always make sure you’re working with an impeccably clean bowl and beater. If you allow some yolk, oil, butter, chocolate, soap or detergent to co-mingle with your egg whites (even in trace amounts!), you’ll end up with a lower volume, relatively coarse foam (meaning large, irregular bubbles).
9. Don’t get salmonella.
Why. Haha, if you have to ask…well, you can check the symptoms on WebMD yourself. Ask anyone who’s ever suffered from a food-borne illness, and they’ll tell you that whatever food they ate wasn’t worth it. Even if you don’t mind consuming raw eggs, consider that the very young, very old, ill, pregnant, and immuno-compromised are more susceptible to food-borne illness than the average healthy adult. They shouldn’t be exposed to salmonella unnecessarily. Recipes for mousses and cocktails often call for raw egg whites, but luckily there are several safe alternatives to choose from. Pasteurized liquid egg whites are available in a carton and are as safe and shelf stable as milk. Powdered egg whites can be kept at room temperature and last quite a long time.
Is it for real? Not every raw egg contains an unhealthy dose of salmonella, but some do, and if you get that unlucky egg, you’ll soon realize how not worth it that raw egg was. Salmonella is naturally present in chicken waste, and although producers remove eggs from the coop as quickly as possible, it’s still likely that the shell has come in contact with salmonella, even if the inside of that particular egg is clean. The simple act of cracking an egg can transfer bacteria from the shell into the inside of the egg. That’s why it’s safest not to consume raw eggs. Pasteurized egg products have been treated with enough heat to kill harmful bacteria like salmonella. The heat of that process also denatures some of the proteins in the egg, which changes the appearance and whipping properties somewhat. For instance, the pasteurized carton egg whites take a bit longer to whip fully, and can be a tad softer, coarser and leakier than regular foam, but it’s surprisingly stable. Even hours later, after all the liquid has drained, it retains more of its original shape than any other foam I’ve ever made.
The proof. On the left in the photo below is a foam whipped from pasteurized carton eggs. On the right is a regular raw egg. As you can see, the carton egg foam is a bit softer and coarser in texture. However, their volumes are very similar, and both were able to reach stiff peaks.
The bottom line. The best alternative (in my experience): pasteurized egg whites from the carton. Just make sure you’re buying 100% real egg whites, not an egg substitute. When I compared the two foams in an uncooked chocolate mousse, the eating experience was almost identical. To me, that’s the most important part! If I can’t tell the difference in the finished item, I really don’t care how they looked as foams!
Powdered egg whites can also be used as a safer substitute for raw eggs, but I have never been able to get them to stiff peaks, plus they tend to leak rapidly and have a yellowish hue. But that’s by no means a final kiss-off to this option. Those symptoms sound similar to the water-added egg. It could be that if I add a little less water than recommended when reconstituting, they might shape up a bit (this theory is yet untested). As another alternative, I’ve heard that some stores carry eggs that are pasteurized in the shell (oh, luxury of luxuries!), but I’ve never seen them myself. If you think you still want to use unpasteurized eggs anyway, please see my suggestions above at number 2.
10. THE MOST IMPORTANT RULE (which almost no recipes ever mention): Take it SLOW.
Why. Whipping too fast right away will give you a foam that’s overbeaten before it even reaches stiff peaks. :(
Is it for real? Absolutely! Even with cream of tartar, if you go in like a NASCAR driver, your egg foam will rebel. Before I learned the importance of this rule, I seemed to always go from soft peaks straight to overbeaten. It made egg foams seem difficult to master, but if I had simply let up on the throttle, I would have had no trouble at all.
The proof. Every picture of an overbeaten foam featured in this post was created by me turning my beater on high right from the get-go.
The bottom line. Even if you’re in a hurry, take things slow at first. If you want to go faster, wait until you’ve got soft peaks. By then your foam is strong enough to handle a little abuse. I use my hand beater on its lowest setting (which is equivalent to about a medium speed on a stand mixer), and a cooperative egg white will beat to stiff peaks in 3-5 minutes. At that rate, rushing couldn’t save a significant amount of time anyway. Never use an immersion blender or food processor in place of an electric beater. You’re much better off just using a old-fashioned whisk. Slow and steady wins the race.
♥ Up next, get ready for some killer recipes that will wow your sweetheart on Valentines! Over the next few weeks, I’ll be revealing recipes for a show-stopping, upscale 3-course feast for two–perfect for an intimate at-home Valentines or special date night. Look out for (SPOILER ALERT!) a knock-your-socks-off goat cheese soufflé, and a decadent chocolate mousse with strawberries and meringue, just to name a few! See you back here soon!