Snap freezing (or cook-chill or blast freezing) is the process of rapid cooling of a substance for the purpose of preservation. It is widely used in the culinary and scientific industries.

Culinary uses

Cooked meals can be preserved by rapid freezing after cooking is complete. The main target group for these products are those with little time for cooking such as

school A school is an educational institution designed to provide learning spaces and learning environments for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is sometimes compu ...

prisons A prison, also known as a jail, gaol (dated, standard English, Australian, and historically in Canada), penitentiary (American English and Canadian English), detention center (or detention centre outside the US), correction center, correc ...

, and hospitals. The process involves the cooking of

meal A meal is an eating occasion that takes place at a certain time and includes consumption of food. The names used for specific meals in English vary, depending on the speaker's culture, the time of day, or the size of the meal. Although they c ...

s at a central factory then rapidly chilling them for storage until they are needed. Snap frozen foods need to be packed in shallow trays to make the process more efficient. The food is cooled to a temperature under 3 degrees Celsius within 90 minutes of cooking and stored at a temperature of 0 to 3 degrees Celsius. The meals can then be transported in refrigerated transport to where the food is to be reheated and consumed when needed. The length of storage depends on the method used but is usually five days. For longer storage the food may be subjected to

pasteurization Pasteurization or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life. T ...

after cooking. These processes have the advantage that preparation and cooking of meals is not tied to the times when the food is to be served, enabling staff and equipment to be used more efficiently. A properly managed operation is capable of supplying high quality meals economically despite high initial equipment costs. There are potential problems; careful attention has to be paid to

hygiene Hygiene is a series of practices performed to preserve health. According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...

as there are a number of points in the process where food

pathogens In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ger ...

can gain access. This requires careful attention to both the control of the process and to staff training.

Scientific use

Snap-freeze is a term often used in scientific papers to describe a process by which a sample is very quickly lowered to temperatures below -70 °C. This is often accomplished by submerging a sample in

liquid nitrogen Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is wi ...

. This prevents water from crystallising when it forms ice, and so better preserves the structure of the sample (e.g.

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

, or live cells){{cite journal , title=Collection, Storage, Retrieval and Distribution of Biological Materials for Research , journal=Cell Preservation Technology , date=1 March 2008 , volume=6 , issue=1 , pages=3–58 , doi=10.1089/cpt.2008.9997

References

Food preservation Heating, ventilation, and air conditioning

Culinary uses

Scientific use

See also

References