Dry ice

Depending on the temperature and pressure, carbon dioxide (CO2) exists in three states – as a gas, liquid or solid. Essentially, dry ice is solid carbon dioxide.
It is made by reducing the pressure and temperature of liquid CO2 till it converts into a clean, white snow. This snow can then be compressed under high pressure to form blocks, slices and pellets.
Because dry ice has no taste or smell, is non-poisonous and non-flammable, it is an ideal and highly- effective cooling and freezing agent for food. It is particularly convenient for in-transit cooling, where power supply can be an issue.