Distilling and Liquid Nitrogen in the Bar Laboratory

Distilling to capture aroma

Tristan Stephenson admits that distilling your own ingredients is not something most home enthusiasts or bars do, but it has been central to his creative work for eight years. Distilling can be seen as infusion and clarification in a single step: boil a mixture of water or alcohol with fruit, herbs, flowers or spices, collect the vapour and condense it. If the starting liquid contained alcohol, the distillate usually has a higher strength, since alcohol boils at a lower temperature than water. What the distiller captures is the aroma of the ingredients, not their taste.

Any still and condenser will work. Commercial gin makers infuse juniper and other botanicals in large pots, but smaller 2 to 5-litre copper pot stills are available, and the author once built a simple glass still from beakers and funnels for under £50. In his bars he uses a rotary evaporator, a rotavap.

The rotavap

Distilling at normal atmospheric pressure needs heat that can damage or change delicate flowers and herbs. A rotavap operates under vacuum, which lowers the boiling point of the liquid and avoids heat spoilage and oxidation. Its parts are a water bath, a rotating flask that holds the mixture, a condenser, which is either an ice-filled cold finger or a coiled tube with coolant from a recirculating chiller, and a vacuum pump. Rotavaps were developed for laboratories, which valued how they separate the components of a liquid by volatility. With practice, balancing pressure against temperature lets a user take out precise parts of an aroma, as a painter picks colour from a palette. Stephenson has used his to make non-alcoholic spirits, to distil peanut butter into bourbon and pineapple husks into rum, and to concentrate fruit juice without heat. A full setup costs at least £5,000.

The law

Distilling alcohol in a cocktail bar, or even at home, in the UK and the US is illegal without a licence. The author’s development lab holds a spirits compounder’s licence, and the products are made there.

Liquid nitrogen

Liquid nitrogen is a tool, not an ingredient, and it is easier to buy than it used to be. At -196 C it can cause cold burns on contact, so gloves and closed shoes are sensible. It must be kept in a purpose-built dewar, which still vents continuously; trying to store it in a sealed vessel will almost certainly cause an explosion. Because it is always venting, a dewar belongs outside or in a well-ventilated room, since the gas can displace oxygen and cause asphyxiation without warning.

Uses of liquid nitrogen in the book include freezing almost anything, including spirits, to make edible cocktail lollipops in a mould; stirring a Martini down in a nitrogen bath to as low as -30 C, colder than a domestic freezer; chilling glasses with a splash; making alcoholic ice cream in under a minute with a creamier texture because the ice crystals are smaller; and infusing spirits quickly by freezing fruit or herbs solid, smashing them to powder and pouring spirit over them. The White Tea Gin of the Pure Brilliant White Lady uses that last method.

Recipes that use these methods

The Pineapple Husk Spirit and the High-Pressure Hydrosol of the Exploded Vodka Martini are examples of distillation. The scan of the book’s liquid nitrogen page has a few unreadable lines, so only the legible statements are used here.