The Benefits Of Dry Ice

Dry ice is carbon dioxide in a solid form. It is used rather like ice from water to rapidly cool all sorts of materials including food. The benefits are mainly from having a much lower temperature than water ice and it never leaves a residue. The material is ideal  for maintaining frozen foods in a way where conventional mechanical freezing is unavailable. It is ideal for keeping foodstuffs cold during transport such as ice-cream, ice lollies and other frozen produce. Meat and poultry processors find it especially useful for reducing temperatures rapidly during processing and maintaining a very cold temperature during transportation of meats. It ‘s also ideal when transporting biological samples especially blood where they are contained within insulated polystyrene boxes.

Chemical Properties 

Dry ice has a freezing point of minus 109 degrees Fahrenheit (minus 78 degrees Celsius). It is worth consulting the freezing point curves for carbon dioxide to get a sense of how it behaves at various food processing temperatures. As dry ice melts, it undergoes a process called sublimation, in which the solid is converted directly into a gas. This is a classic example of the process – the only other chemical that is usually encountered showing such behaviour is iodine.

Availability

Dry ice is typically produced in three standard forms:

• large blocks or chunks which are broken up with a an ice pick for easier handling
• cylindrical small (¹⁄₂ or ⁵⁄₈ inch [13 or 16 mm] diameter) pellets often of varying length. The density of the pellets are between 1.4 to 1.6 g/cm³
• cylindrical tiny (¹⁄₈ inch [3.2 mm] diameter), high surface to volume pellets that float on oil or water and do not stick to skin because of their high radii of curvature. 

Uses

Dry ice is ideal for special occasions, celebrations and parties where a centre piece is required with  a white spectral-like cloud  which flows over the surface. The cloud is actually a fog because this white cloud is made up of frozen water droplets. These are heavier than air which falls to the ground. When the water they are added to for example is hotter, the effect of the cloud is even more dramatic. It should not be used in water which is warmer than 80 Centigrade because the fog just disappears upwards.

Dry ice is used in the pre-fermentation maceration process for rapid cooling of materials and for aiding extraction. It sublimes away so there is no residue or addition in weight to the product.

Safety Regulations

Dry ice should be kept in small quantities in an insulated “cold box” or similar transport medium that is maintained at (-94.0^ºF (-70.0^ºC) or in an open, well-ventilated space. When a company ships dry ice the shipment must be prepared by an employee trained in the Dangerous Goods regulations of the respective countries.

It is dangerous to handle without skin protection so gloves are always worn otherwise frost bite and burn is possible. It must be used in a well ventilated area because it readily sublimes to its gaseous form.

Carbon dioxide in its own right is not poisonous but it will be an issue if confined in a tight place where on sublimation it builds up pressure and displaces atmospheric air. When dry ice is not stored properly and contained in a place with poor ventilation, then people will inhale large amounts of carbon dioxide which displaces oxygen in the bloodstream. The effect is to produce confusion, headache, disorientation and death. Respiratory and CNS changes can occur within seconds of exposure to high levels of CO₂, suggesting that the toxicity of CO₂ might be related to systemic effects that are not fully understood.

Persons with signs or symptoms of illness while exposed to dry ice should be moved to an area with fresh air and provided with supplemental oxygen. Usually, the long-term outcome for patients with mild-to-moderate CO₂ poisoning is excellent. 

The Center For Disease Control has reported all those  incidents where dry ice has caused serious illness  as reported in 2004. In that example dry ice was used because normal refrigeration methods had been knocked out by hurricanes.         

 According to United nations regulations, dry ice refrigerant using either of the proper shipping names  DRY ICE or CARBON DIOXIDE. SOLID must be assigned to UN 1845.   Dry ice is not a dangerous or hazardous material according to the United Sates Department of Transportation or the European Union for ground transport. When shipped by air or sea then particular regulations apply  it is treated as a dangerous good and carries the IATA packaging instruction 954 (IATA PI 954). This takes the form of a diamond-shaped black and white label.                                                                   

Commercial Forms Of Dry Ice

A new product known as ALIGAL™ Blue Ice (ABI) incorporates ozone in dry ice pellets, combining the high cooling capacity of dry ice pellets and the antimicrobial efficacy of ozone. It has been tested as an antimicrobial agent which is suitable for destroying food poisoning micro-organisms.

Typical producers include Air Liquide.

References

Baxter, P.J., Kapila, M., Mfonfu, D. (1989) Lake Nyos disaster, Cameroon, 1986. The medical effects of large scale emission of carbon dioxide? BMJ 298 pp. 1437-41.