The quick-freezing process of food preservation was developed in the early 20th century by the american inventor Clarence Birdseye.
Flash freezing (aka blast freezing) is the process in which different objects are quickly frozen by subjecting them to cryogenic temperatures. It is mostly used in the food industry in order to quickly freeze perishable food items. In this kind of situation, food is subjected to very low temperatures – below water’s melting/freezing point (32°F or 0°C), making possible the instant freeze of the water inside the foods, without forming large crystals, thus avoiding damage to cell membranes.
From the exact same reason (not damaging the samples), flash freezing is also used to freeze biological samples. This rapid freezing is done by submerging the sample in liquid nitrogen or a mixture of dry ice and ethanol.
A supercooled liquid will stay in a liquid state below the normal freezing point when it has little opportunity for nucleation; this happens if it is pure enough and has a good enough container. Once agitated it will rapidly become a solid.