Freezing food very rapidly with intensely cold, fast-moving air so it reaches a frozen state quickly and keeps its quality.
Freezing food very rapidly with intensely cold, fast-moving air so it reaches a frozen state quickly and keeps its quality. Blast freezing is the process of freezing food quickly by surrounding it with very cold, high-velocity air. The speed matters because slow freezing lets large ice crystals form inside food, which damages its texture and can degrade quality. Rapid freezing produces smaller ice crystals, so the food is better preserved and closer to its original state when thawed. From a food-safety point of view, blast freezing quickly takes food below the temperatures at which food-poisoning bacteria can grow. While freezing does not kill most bacteria, it stops them multiplying, so getting food frozen fast and then holding it in frozen storage limits any bacterial growth during the transition. Under Australian practice, food to be frozen should already be safe and, where relevant, cooled correctly before freezing rather than relying on the freezer to fix an earlier temperature-control failure. Australian manufacturers and larger kitchens use blast freezers for products such as portioned meats, seafood, bakery items and prepared meals. Staff load food in a single layer or shallow trays so cold air reaches all surfaces, then hold it until it is frozen solid before transferring it to a normal freezer or cold store running at a stable frozen temperature. Because freezing preserves food in the condition it was in when frozen, the food must be fresh and handled hygienically beforehand. Frozen items should be labelled and date-marked so stock is rotated correctly, and the freezer temperature should be monitored so food stays frozen throughout storage and transport. A seafood processor blast freezes fillets within hours of filleting. The fillets are laid in a single layer and frozen hard in a blast freezer before being bagged, labelled with the freezing date and moved to the main frozen store, which keeps the flesh firm and limits quality loss compared with slow freezing in a domestic-style freezer.
Frequently asked questions
Why freeze food quickly rather than slowly?
Fast freezing forms smaller ice crystals, which protects texture and quality. Slow freezing forms large crystals that damage the food's structure.
Does blast freezing kill bacteria?
No. Freezing stops most bacteria multiplying but does not reliably kill them. They can become active again once the food thaws, so hygienic handling before and after still matters.
Can I freeze hot food directly in a blast freezer?
It is better to cool cooked food correctly first. Freezing should preserve already-safe food rather than being used to rescue food that was cooled too slowly.
How is blast freezing different from blast chilling?
Blast chilling cools food to fridge temperature around 5 degrees C, while blast freezing takes it well below zero to a frozen state for longer storage.
Should frozen food be labelled?
Yes. Date-mark and label frozen food so it can be rotated and used in order, and so you know how long it has been in frozen storage.
