Shock freezing, or blast freezing, works on the same principle as blast chilling but goes further, taking the food core well below freezing. A commonly cited benchmark is reaching around −18 °C at the core within about four hours from cooked temperature. Many cabinets do both jobs and are sold as blast chiller-freezers.
Speed matters because of ice crystal size. When food freezes slowly, water forms large crystals that rupture cell walls; on thawing, the food leaks moisture and turns soft or grainy. Fast freezing forms smaller crystals and keeps texture closer to fresh. That is why shock freezing is used for pastry, laminated dough, seafood, ready meals and gelato bases.
A bakery in Mumbai supplying croissants to several cafés might shape and shock-freeze them unbaked, then store them in an ordinary freezer. Each café bakes off what it needs. A shock freezer is a process tool: once frozen, food moves to storage freezers, which only need to hold temperature.