In certain cocktails, a foam can be the essential ingredient that turns an otherwise flat and uninteresting drink into a textured and complex tipple, a light and fluffy introduction onto your palate of the flavors waiting underneath, the gentle kiss before the punch as it were. What would a Clover Club be without that silky sensation, the density of weight giving way to the well-chilled drink beneath, giving a luxurious texture to what could otherwise be an unremarkable drink?
But how and why do these layers form? The answer is protein; egg whites are around 92% water, and 8% protein, tightly bonded spirals that contain amino acids. By emulsifying an egg white via whisking or dry-shaking, you break this protein shell and expose the amino acids, some of which are hydrophillic and some of which are hydrophobic, that is, some are attracted to water and some are repelled by it.
As such, the rapid agitation introduced by your emulsification causes the hydrophillic amino acids to gather close to water, and the hydrophobic ones to gather close to the air introduced into the mix. This causes the protein strands to unfold and bond to other adjacent proteins, forming a network of bonds that make up the body of the foam.
The more you emulsify the stiffer the foam will get until all the proteins have unfurled. In a solution (say, a cocktail for example), the linked proteins will rise to the surface of the drink due to the air bubbles being lighter than the liquid surrounding it. Protein will continue to bond with adjacent protein, so after 30 seconds there will be a layered separation of liquid and bonded proteins, i.e. the foam.
Simple, right? Well not so much. Egg white isn't the only ingredient in your drink that can contain the combination of protein and acids that can create a foam, and there are myriad reasons that can lead to your foam being too thin, dissolving too quickly, or just looking sad and flaccid.
The higher the alcohol content in the cocktail, the lower the ratio of bonds formed so less foam; this will also create weaker bonds that will break apart much quicker than in a solution with lower alcohol.
Likewise, the ratios of sugar and acid in the solution will affect how well your bubbles form - consider the drink as you would consider a delicate meringue; sugar acts as a stabiliser while emulsifying, creating stronger, but smaller bonds. The higher the sugar content, the denser the foam will be. Acidity is another variable - if a solution is too acidic then bonds will begin to weaken and collapse very quickly after settling, leaving you with a deflated and unpleasant looking foam.
Another factor is the freshness and temperature of the egg white used in the recipe. Refrigerated whites will be slow to emulsify, taking much longer than with room temperature whites, and the ideal age of an egg will be 2-3 days after laying. Eggs that are too fresh will produce a white that visibly separates when cracked: a thin, watery liquid will separate from the jelly-like inner white, known as the ovomucin. Ovomucin acts as a trypsin inhibitor, trypsin being a enzyme that breaks down proteins and occurs naturally in digestion and is present in the egg when it is laid.
The older an egg is the weaker the proteins become as the ovomucin degrades and the trypsin starts to break down the proteins in the albumen, and the weaker and thinner the resultant foam will appear. For long term storage pasteurisation works as a solution to denaturalise the enzymes in egg white, however the egg white can still spoil for bacterial reasons.
An ideal solution for any high-volume usage of egg white would be the use of dehydrated albumen, as it takes up less space, does not spoil in it's dry form and is consistent in it's protein content across a batch - eggs are of course, at the end of the day an organic product and never consistent from egg to egg. Just place egg white in a shallow pan and put it into a dehydrator (under 65c, or else you'll end up with a large omelette) and blend it once dried - store somewhere dry.
A bar spoon per drink is about perfect, and just dry shake and wet shake as you would using egg white. The only thing you have to adjust for using this method is the liquid volume you are losing without hydrated egg white - remember your wash lines before spinning this method out.
It goes without saying but of course you shouldn't be using cage eggs - poor nutrition in the chickens mean a low protein count and a watery egg white and a poor foam. Also it's incredibly cruel.
Egg white isn't suitable for every drinker however, as people with dietary concerns or squeamish individuals shy away from a drink when they see egg white going into the mix. Therefore it is worth investigating other options to create the same affect in a cocktail.
One such option is pineapple juice - pineapple has a high level of protein and creates a thick, foamy head when emulsified as a result of the high level of fruit sugars in ripe pineapple acting as a stabiliser for the foam.
However in the core of pineapple exists an enzyme called bromelain, which is a digestive enzyme similar to trypsin in the way it attacks proteins. If you have ever sliced up a load of fresh pineapple and felt a tickling sensation on your fingers that is bromelain digesting your skin; it's a commonly used ingredient as a meat tenderiser. To avoid the proteins in your pineapple juice from breaking down, one you have juiced the pineapple flesh, bring it quickly to boil to denaturalise the enzymes. Once cooled, the juice will last for two days and provide a gorgeous head every time.
Another option is to use a soy-derived protein - soy lecithin will give you the same result in terms of creating protein strands when emulsified - however a higher sugar content in a drink will make a more stable foam in the finished product as soy proteins create a weaker bond and require more stabiliser.
The higher the alcohol content in the cocktail, the lower the ratio of bonds formed so less foam; this will also create weaker bonds that will break apart much quicker than in a solution with lower alcohol.
Likewise, the ratios of sugar and acid in the solution will affect how well your bubbles form - consider the drink as you would consider a delicate meringue; sugar acts as a stabiliser while emulsifying, creating stronger, but smaller bonds. The higher the sugar content, the denser the foam will be. Acidity is another variable - if a solution is too acidic then bonds will begin to weaken and collapse very quickly after settling, leaving you with a deflated and unpleasant looking foam.
Another factor is the freshness and temperature of the egg white used in the recipe. Refrigerated whites will be slow to emulsify, taking much longer than with room temperature whites, and the ideal age of an egg will be 2-3 days after laying. Eggs that are too fresh will produce a white that visibly separates when cracked: a thin, watery liquid will separate from the jelly-like inner white, known as the ovomucin. Ovomucin acts as a trypsin inhibitor, trypsin being a enzyme that breaks down proteins and occurs naturally in digestion and is present in the egg when it is laid.
The older an egg is the weaker the proteins become as the ovomucin degrades and the trypsin starts to break down the proteins in the albumen, and the weaker and thinner the resultant foam will appear. For long term storage pasteurisation works as a solution to denaturalise the enzymes in egg white, however the egg white can still spoil for bacterial reasons.
An ideal solution for any high-volume usage of egg white would be the use of dehydrated albumen, as it takes up less space, does not spoil in it's dry form and is consistent in it's protein content across a batch - eggs are of course, at the end of the day an organic product and never consistent from egg to egg. Just place egg white in a shallow pan and put it into a dehydrator (under 65c, or else you'll end up with a large omelette) and blend it once dried - store somewhere dry.
A bar spoon per drink is about perfect, and just dry shake and wet shake as you would using egg white. The only thing you have to adjust for using this method is the liquid volume you are losing without hydrated egg white - remember your wash lines before spinning this method out.
It goes without saying but of course you shouldn't be using cage eggs - poor nutrition in the chickens mean a low protein count and a watery egg white and a poor foam. Also it's incredibly cruel.
Egg white isn't suitable for every drinker however, as people with dietary concerns or squeamish individuals shy away from a drink when they see egg white going into the mix. Therefore it is worth investigating other options to create the same affect in a cocktail.
One such option is pineapple juice - pineapple has a high level of protein and creates a thick, foamy head when emulsified as a result of the high level of fruit sugars in ripe pineapple acting as a stabiliser for the foam.
However in the core of pineapple exists an enzyme called bromelain, which is a digestive enzyme similar to trypsin in the way it attacks proteins. If you have ever sliced up a load of fresh pineapple and felt a tickling sensation on your fingers that is bromelain digesting your skin; it's a commonly used ingredient as a meat tenderiser. To avoid the proteins in your pineapple juice from breaking down, one you have juiced the pineapple flesh, bring it quickly to boil to denaturalise the enzymes. Once cooled, the juice will last for two days and provide a gorgeous head every time.
Another option is to use a soy-derived protein - soy lecithin will give you the same result in terms of creating protein strands when emulsified - however a higher sugar content in a drink will make a more stable foam in the finished product as soy proteins create a weaker bond and require more stabiliser.
In terms of methods of emulsification, there are a few methods to properly activate the proteins for a final drink:
- The classic dry shake: shaking the cocktail without ice first to aerate and blend the mix. (A common question is why is it called a dry shake when the shaker contains liquid? The answer of course being that it is shaken without ice first so no dilution is achieved - hence keeping it dry.)
-A whipping article added to the shaker: classically the spring from a hawthorn strainer added to a shaker and dry shaken, although this is messy and somewhat of a ball ache. Other items that can assist are the metal balls from protein shakers, while Alcademic's Camper English suggests cat toys.
-Immersion blender: A stick blender can do wonders in quickly whipping proteins into light, fluffy piles before shaking, and removes the hassle of a double shake.
-The inverse dry shake: friend and occasional nemesis Jay Gray espouses the benefits of the inverse dry shake; that is, shaking with ice first, fine straining the mix, then dry shaking it before serving. I'm not 100% sold on the science of this, as diluting the mix first would in theory result in weaker protein bonds in the final solution. He swears by it's efficacy however, and I swear against it, and then we both swear at each other.
-The crushed ice time saver: Popularised at Bulletin place, this method does away with the dry shake, with crushed ice pulling double duty as both a diluter and emulsifier, which is then fine strained out of the final drink and resulting in a consistent and silky smooth finish to the drink.
Finally, I thought I'd add a recipe from a few months ago for a vegan-appropriate amaretto sour using soya lecithin extract; it is distressing how many people enjoyed this one
- The classic dry shake: shaking the cocktail without ice first to aerate and blend the mix. (A common question is why is it called a dry shake when the shaker contains liquid? The answer of course being that it is shaken without ice first so no dilution is achieved - hence keeping it dry.)
-A whipping article added to the shaker: classically the spring from a hawthorn strainer added to a shaker and dry shaken, although this is messy and somewhat of a ball ache. Other items that can assist are the metal balls from protein shakers, while Alcademic's Camper English suggests cat toys.
-Immersion blender: A stick blender can do wonders in quickly whipping proteins into light, fluffy piles before shaking, and removes the hassle of a double shake.
-The inverse dry shake: friend and occasional nemesis Jay Gray espouses the benefits of the inverse dry shake; that is, shaking with ice first, fine straining the mix, then dry shaking it before serving. I'm not 100% sold on the science of this, as diluting the mix first would in theory result in weaker protein bonds in the final solution. He swears by it's efficacy however, and I swear against it, and then we both swear at each other.
-The crushed ice time saver: Popularised at Bulletin place, this method does away with the dry shake, with crushed ice pulling double duty as both a diluter and emulsifier, which is then fine strained out of the final drink and resulting in a consistent and silky smooth finish to the drink.
Finally, I thought I'd add a recipe from a few months ago for a vegan-appropriate amaretto sour using soya lecithin extract; it is distressing how many people enjoyed this one
The Lagomorph
nb: Lagomorph being the genus name for rabbits. No, my jokes aren't funny in person, either.
45ml Amaretto
15ml Amaro Averna
30ml Blanched carrot juice
20ml lemon juice
1 bsp soya lecithin
Dry shake vigorously, wet shake and strain into a chilled sour glass.
Garnish with dehydrated "Rabbit Ears"
