How Does Milk Clarify Cocktails?

The Science Behind Clarified Cocktails

Clarified cocktail at Cavana in San Francisco. Photo by Camper English

There are two distinct drinks called milk punch. The first is usually found in the form of Bourbon Milk Punch, and it is common to see it on menus in New Orleans along with Ramos Gin Fizzes and Sazeracs. It contains bourbon, milk, simple syrup, and vanilla extract.

The second is Clarified Milk Punch, sometimes called British Milk Punch or just listed on modern bar menus as a cocktail that is milk-washed or milk-clarified.

The Bourbon Milk Punch tastes and looks milky white. The clarified one is clear or lightly colored but translucent. The drink is silky in texture, and any woody or tannic flavors from barrel-aged spirits or tea, for example, are softened.

Milk clarification is a process that can be applied to almost any drink (or even just a base spirit), rather than a recipe for one cocktail. Let’s discuss how it works.

Curds and Clumps

Clumpy milk punch photo credit @katrinastarchild

People of a certain age may remember a horrible drink called the Cement Mixer. It is Irish cream liqueur topped with a layer of lime juice, then taken in the form of a shot. You were instructed to swish it around in your mouth, at which point the cream would curdle and the drink would become chunky. Yuck.

Milk punch uses the same curdling reaction – mixing an acidic ingredient into a milky one – but with far better looking and less clumpy results. Instead of lime juice, an acidic cocktail is used – and nearly all cocktails are acidic.

Let’s take a Cosmopolitan for example – we can make a Clarified Cosmo with the milk punch technique. We take a batch of Cosmopolitans and pour some of it into some milk in a container. The milk starts to curdle. Then we slowly add the rest of the acidic cocktail to the milk and let it rest a while. Then we pour the clumpy mixture through a filter like a coffee filter once or twice. The curdled chunks stay behind in the filter, and the resulting Cosmo is light pink but crystal clear; almost shiny. There is no cloudiness from the lime juice, and you can see right through it.

The crucial thing to understand about this process is that the filter is not doing the clarifying. The curds are.

The Soup Parallel

Milk punch photo credit @katrinastarchild

So how do curds clarify a cocktail? There is a parallel in consommé, the soup stock that is made from chopped meat and vegetables then clarified with egg whites. Harold McGee wrote about this in his 1984 book On Food And Cooking: The Science And Lore Of The Kitchen.

He describes the process of combining meat/vegetables in cold soup stock with lightly whisked egg whites. “As the stock heats up, the abundant egg white proteins begin to coagulate into a fine cheesecloth-like network, and essentially strain the liquid from within…. Gradually the protein mesh rises to the top of the pot to form a ‘raft,’ which continues to collect particles.”

Milk punch is similar, except the proteins come from the milk solids rather than egg whites, and the curds are the raft – which sinks rather than floats. Proteins in milk start out as compact folded shapes, then when acid from the cocktail is added (instead of heat for the egg whites) the proteins get scrambled and clump together. These clumps make a 3D net of sorts, trapping even the tiniest bits of pulp and other suspended particles.

A Web of Ryes

Straining milk punch photo credit @katrinastarchild

Running the cocktail through the curds keeps the solids in the protein web, and allows the liquids to run out. The coffee filter is used only to hold back the curds from going into our glass. This latter point is the key to understanding why your milk punch is working to clarify or not. Many people concentrate on the filter, but it’s all about the quality of the curds.

You can similarly clarify a cocktail with gelatin or agar-agar instead of milk or egg. In this case the solid bits are caught in the gel and the liquid runs through. Both techniques are described in Dave Arnold’s book Liquid Intelligence.

Tannins and polyphenols are also removed during the clarification process. Tannins can come from over-steeped tea, too-woody whiskey, and grape skins used in red wine, and cause the astringent, gripping sensation in our mouths. Tannins bind with the proteins in the milk (instead of with proteins in our saliva) and they are removed from the cocktail.

A similar thing happens in cocktails with egg white foam – the foam softens the impact of tannins. Think of a Whiskey Sour made with or without egg white, or the softness of Audrey Saunders’ Earl Grey MarTEAni.

Many recipes for Milk Punch call for tea in the recipe for this reason – you can over-steep the tea in an infusion, but the bitter tannins will be stripped out at the end. The milk punch clarification technique is simple to perform, but a little tricky to understand at first. It’s surprising that the oldest recipe for one, Mary Rockett’s Milk Punch, dates to 1711!