Liquid Nitrogen & Dry Ice
What is Liquid Nitrogen?
Liquid nitrogen is a cryogenic product supplied by specialist cryogenics companies such as Mansfield Cryogenics Ltd.
Basically, liquid nitrogen is nitrogen which is held in a liquid state at a very low temperature. At normal atmospheric pressure liquid nitrogen boils at -196° C and is a cryogenic fluid which causes rapid freezing on contact with food and fresh produce. The use of liquid nitrogen in the Food Industry is well established in the frozen foods market. However, in recent years chefs like Heston Blumenthal, Ferran and Albert Adrià, Dani Garcia and Kristof Coppens, to name but a few, have openly developed the use of liquid nitrogen cooking into an avant-garde cooking technique.
On immediate contact with food, liquid nitrogen boils and envelops food, rapidly evaporating the liquid nitrogen into plumes of nitrogen gas bubbles which crystalise and freeze. As a result a kind of "steam" of nitrogen bubbles is formed which solidifies into micro-crystals to freeze food instantaneously. Whereas freezing food with a conventional freezer can form large ice crystals within the products that degrade their integrity and nutritional value, smaller ice crystals are formed when flash freezing with nitrogen, keeping foods intact and making for ultra smooth textures, non-existent freezing affects in the mouth and intensified smells and flavours.
Chefs can use liquid nitrogen in their cooking in many various ways, including, instantaneous ice cream or sorbets; quick freezing of ingredients for grinding or effortlessly breaking into pieces; interesting textural and visual variations
- for instance, perfect sweet/savoury spheres of purées with hard shells and flavoured creams that look like popcorn; making liquid centres for meringues and truffles; creating fun dishes like popcorn, real and faux meringues and aerated cakes that create a "dragon's breath" affect when the diner exhales "smoke" through their nostrils; and for performing creations in front of the customer like lollipops, ice cold moulds and chocolate spaghetti on a Nitro-Teppan or anti-griddle.
Storage, Consumption & Safety
Liquid nitrogen for cooking is relatively inexpensive to obtain from a specialist cryogenics/gas company, a litre makes about two litres of ice cream. To obtain it, store it and use it safely does however demand the proper insurance, equipment and training in handling this potentially hazardous material. Key points include:
Storage
Once dispensed from your gas supplier, liquid nitrogen must only be kept in a special open storage container or one with a pressure valve to prevent the vessel exploding. Liquid nitrogen can increase its volume almost 700 times and if pressure builds will explode. Whilst these storage containers are good for holding larger volumes of liquid nitrogen outside the kitchen, once inside the kitchen and performing tasks with foods and cooking it is best to pour it into a Dewar flask or Pyrex® cryo bowl. These flasks and bowls are either vacuum insulated or double walled to prevent transfer of heat and reduce consumption through evaporation. Many chefs use stainless steel saucepans which become dangerously cold to touch and glass bowls will shatter. Some kitchen tasks and all front of customer tasks can be used on a Nitro-Teppan which performs the function of an anti-griddle.
Consumption
Once dispensed from your gas supplier, liquid nitrogen must only be kept in a special open storage container or one with a pressure valve to prevent the vessel exploding. Liquid nitrogen can increase its volume almost 700 times and if pressure builds will explode. Whilst these storage containers are good for holding larger volumes of liquid nitrogen outside the kitchen, once inside the kitchen and performing tasks with foods and cooking it is best to pour it into a Dewar flask or Pyrex® cryo bowl. These flasks and bowls are either vacuum insulated or double walled to prevent transfer of heat and reduce consumption through evaporation. Many chefs use stainless steel saucepans which become dangerously cold to touch and glass bowls will shatter. Some kitchen tasks and all front of customer tasks can be used on a Nitro-Teppan which performs the function of an anti-griddle.
Safety
Needless to say extreme cold can cause serious burns. It is pre-requisite that those handling liquid nitrogen should wear non-absorbent gloves, anti-splash goggles or gloves and aprons. The eyes are particularly vulnerable because even a small splash could cause irreparable damage. Liquid nitrogen should also only be used in well ventilated spaces so that it does not displace oxygen in the air supply and cause asphyxiation. And finally, liquid nitrogen makes for extremely cold food. If something is frozen solid, it will need to warm up before diners can eat it safely.
What is Dry Ice
Dry ice is different from liquid nitrogen in that it is the solid form of Carbon Dioxide. It is obtained by reducing the pressure and temperature of CO2 in a controlled manner and changes the liquid into a pure snow like form. Dry ice is used in the Food Industry to refrigerate and transport foods that should be kept at low temperatures without exposure to moisture. Making dry ice in avant-garde cooking is generally for visual affect or as an aroma vaporiser and is less hazardous to handle by chefs and diners.
Whilst Culinary Innovations does not supply liquid nitrogen, we do supply the storage containers and tools that a chef will need to use once the cryogenic was installed on-site.
© Copyright 2013 Culinary Innovations Ltd