Blast freezers
A blast freezer is a freezer that blows very cold air at high velocity over food to freeze it quickly, much faster than an ordinary cold store could. Blast freezers sit after cooking, blanching, forming or packing and before frozen storage. On a french fry line product goes from the fryer through cooling into a freezer; on a vegetable line from the blancher and dewatering into the freezer; in a bakery or ready-meal plant from the oven or assembly line into the freezer, and then into frozen storage. The freezer's job is to bring product through the freezing zone, where most of its water turns to ice, as quickly as practical. Fast freezing forms small ice crystals that cause less damage to cell structure, so thawed product keeps better texture and loses less drip. It also limits the time product spends at temperatures where micro-organisms can grow. Blast freezers take many forms. Batch blast freezers and blast rooms freeze trolleys or pallets of product and suit smaller plants and varied products. Continuous freezers carry product on a belt: spiral freezers wind the belt around a drum to fit a long freezing time into a small footprint, and are common for bakery, meat, poultry and ready meals; tunnel freezers move product in a straight line; fluidised-bed freezers lift small pieces such as peas, diced vegetables and fries on an upward air stream so each piece freezes separately, which is known as individual quick freezing; and impingement freezers direct high-speed air jets at thin products. Cryogenic freezers use liquid nitrogen or carbon dioxide instead of mechanical refrigeration and freeze very fast, with a lower equipment cost but a continuous cost for the refrigerant gas. Mechanical blast freezers use refrigerants such as ammonia, carbon dioxide or synthetic refrigerants. Regulations in many countries are phasing down synthetic refrigerants with high global warming potential, which affects long-term running and service costs. Cost and performance depend on capacity, the freezing time your product needs, freezer type, refrigeration plant and refrigerant, energy efficiency, defrost system, hygiene design and footprint.
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Buying criteria
Start with the product: its size, shape, packaging, entry temperature and the final temperature required. These decide freezing time and the freezer type. Choose between batch, spiral, tunnel, fluidised-bed, impingement and cryogenic freezing based on product, throughput and floor space. Look at refrigerant and energy. Refrigeration runs continuously, so efficiency drives running cost. Check the regulatory outlook for the refrigerant in your country and the skills available to service it. Check defrost arrangements and how long the freezer can run between defrosts and cleans. Review hygiene: cleaning access, drainage, belt washing and the materials used inside the freezer. Finally, check the footprint and building requirements, how product is loaded and unloaded, and how the freezer connects to cold storage without warming product on the way. Ask for freezing trials on your own product where possible, since published capacities depend on product and entry temperature.
Buyers ask
How much does a blast freezer cost?
It depends on capacity, freezing time, freezer type and the refrigeration plant behind it. A batch blast room costs far less than a continuous spiral or fluidised-bed freezer. The refrigeration plant, refrigerant choice, building work, insulation and electrical supply often form a large part of the total. Cryogenic freezers cost less to buy but carry an ongoing gas cost.
What is the difference between a blast freezer and a cold store?
A blast freezer is built to freeze product quickly, using high-velocity cold air and a large refrigeration capacity. A cold store is built to hold already-frozen product at a steady temperature. Putting unfrozen product into a cold store freezes it slowly, which harms quality and can raise the store's temperature.
What is IQF freezing?
IQF means individually quick frozen. Small pieces such as peas, diced vegetables, berries or fries are frozen separately, usually in a fluidised-bed or tunnel freezer, so they do not stick together. Customers can then pour out the amount they need.
What is a spiral freezer?
A spiral freezer carries product on a belt that winds around a rotating drum inside an insulated enclosure. The spiral fits a long belt, and therefore a long freezing time, into a compact footprint. It is common for bakery, meat, poultry, seafood and ready meals.
Is cryogenic freezing better than mechanical freezing?
Neither is better in all cases. Cryogenic freezing with liquid nitrogen or carbon dioxide freezes very quickly, needs less equipment and suits seasonal or delicate products, but the gas is a continuous cost. Mechanical freezing costs more to install but usually less to run at high, steady volumes.