The Sous Vide technique involves ingredients being vacuum packed and then slowly cooked in water at an accurately controlled temperature.
The exclusion of air in the vacuum bag greatly reduces the growth of aerobic bacteria, and this delays the contents from spoiling.
Sous-vide is French for "under vacuum". It is a method of cooking that is intended to maintain the integrity of ingredients by heating them for an extended period of time at relatively low temperatures. Food is cooked for a long time, sometimes well over 24 hours. Unlike cooking in a slow cooker, sous-vide cooking uses airtight plastic bags placed in hot water well below boiling point (usually around 60°C or 140°F).
The method was developed by Georges Pralus in the mid-1970s for the Restaurant Troisgros (of Pierre and Michel Troigros) in Roanne, France. He discovered that when cooking foie gras in this manner it kept its original appearance, did not lose excess amounts of fat and had better texture. Another pioneer in the science of sous-vide is Bruno Goussault, who further researched the effects of temperature on various foods and became well-known for training top chefs in the method. As Chief Scientist of Cuisine Solutions, Goussault thoroughly developed the parameters of cooking times and temperatures for different foods.
The sous-vide method is used in several gourmet restaurants under Thomas Keller, Jesse Mallgren, Paul Bocuse, Joël Robuchon, Charlie Trotter, and other chefs.
Amtrak has used this method of cooking in the dining cars of its long-distance trains, and recently began using the method on its Acela Express trains. Non-professional cooks are also beginning to use vacuum cooking.
Clostridium botulinum bacteria can grow in food in the absence of oxygen and produce the deadly botulinum toxin, so sous-vide cooking must be performed under carefully controlled conditions to avoid botulism poisoning. To help with food safety and taste, relatively expensive water-bath machines (thermal immersion circulators) are used to circulate precisely heated water. Differences of even one degree can affect the finished product.
In the USA and other English speaking countries, the technique of vacuum packaging may be known as Cryovaccing
Cooking at lower temperatures for extended periods of time has a wide range of benefits:
· Minimal loss of moisture and weight
· Preservation of flavour and aroma as water soluble substances - especially aromatics - are not lost
· Flavours are enhanced, colours retained and little or no salt is required
· Nutrients are preserved as water-soluble minerals are not leached into cooking water, as cooking in a vacuum bag eliminates this
· Research has shown that sous vide gives the highest retention of vitamins vs. steaming and boiling
· Little additional fat is required during cooking
· Consistent results every time a dish is cooked
As chefs the world over are aware, these benefits result in enhanced textures, flavours and tenderness.
Because Sous Vide involves specific cooking times and precise temperatures, the risk of human error is eliminated provided the right equipment is used.
Sous Vide allows kitchens to maximise advance preparation. Provided the food is chilled quickly after the cooking process has finished, it can be safely stored until needed. It also reduces wastage, making sous vide a highly cost effective cooking method.
Sous vide gives kitchens substantial operational benefits:
· Minimise wastage by advance preparation of controlled portions
· Minimum shrinkage of contents during cooking process, typically from 30% to less than 5% in most cases resulting in greater yield.
· Cheaper cuts of meat can be used as the sous vide technique dramatically improves tenderness
· Extra demand can be drawn from cold store or less used in quieter periods
· Low energy consumption compared with ovens and gas ranges
· Non-use of gas reduces ambient temperature in kitchen, and fire risk
· Several meals from starter to dessert can be regenerated simultaneously in the same bath reducing clean up time
· With minimal training, unskilled staff can use the equipment, this simplifies service and is especially useful for room service during the night
· Work planning, preparation and cooking outside of service times is improved, e.g. planning ahead for banquet preparation
· As garnishing plates/mis en place work can take place whilst service items are poaching, valuable time is save
The amount of time saved creates an opportunity to enable more development work, which leads to improved job satisfaction
· Extending menu content and planning
· Operational procedures
When using the sous vide method, it is vital to establish procedures and policies to demonstrate that all efforts have been taken to minimise the risk from anaerobic bacteria e.g. clostridium botulinum.
Typical Steps to Establish a Food Safety Policy:
· Source only the highest quality ingredients from known suppliers and have a system of traceability in place.
· Separate food areas for raw and cooked.
· Establish minimum cooking temperatures for meat and fish.
· Adhere to maximum storage temperatures and times.
· Strict labelling of contents with date (including expiry date) and identification of contents.
· Consider using disposable sterile gloves when filling sous vide bags.
· Use two separate vacuum machines, one for raw and other for cooked foods
· Put in place HACCP - Hazards Analysis and Critical Control Point Programme
This covers the movement of food from delivery to service.
Identify points of risk - some if which may include the following:
· Quality of water in Kitchen
· Potential breaks in the 'cold chain'
· Unnecessary 'holding' time
· Potential contamination points with other foods/ items in the kitchen environment
· Improper stock identification and rotation
· Time taken to cool cooked food for storage
It is recommended that the cooking temperature should be greater than 65ºC to ensure pasteurisation. However enough time to ensure that the core temperature has been reached must be allowed. This can be done at trial stage by using a probe and digital thermometer.
Ideally temperatures should not exceed 70ºC to ensure that the moisture and flavour is not lost. Cooking in this way is ideal for mis en place (indirect) as the storage and preservation of the product will last a great deal longer.
Direct cooking can be done at lower temperatures as long as the food is consumed immediately. The risk of bacterial multiplication is small as the length of time the ingredients stay in the risk zone is minimal. It is vital however that the ingredients are as fresh as possible.