We’re wrapping up Frozen Food Month with an entry on blast freezing. What is it? Why does Americold use it? How can it benefit you?
Imagine it’s 6 pm. You wrap up work, the house is a mess, and the kids are hungry. You need a speedy meal solution so you turn to the trusty freezer. From precooked chicken tenders to veggies to ice cream, your frozen food options are almost limitless these days. It’s a convenience many take for granted and one that can be attributed to an invention that’s less than 100 years old.
Freezing food slows molecular and microbial activity, effectively extending product shelf life. When a product is frozen, its temperature decreases and some of the water in the product crystalizes. Traditional freezing entails putting food into a cold, temperature-controlled environment. It’s an effective method but takes time and the slower freezing process means the water forms large ice crystals that disrupt some food structures and subsequently deteriorates product quality over time.
Flash freezing, also known as blast freezing, was introduced by Clarence Birdseye (founder of the Birds Eye brand) in 1929. He discovered the process from watching fish being pulled up from under the ice in northern climates during the winter. Birdseye noticed the fish froze very quickly but maintained their texture when they were thawed. Attributing the fish's meat integrity to the quick freezing process and the minimal size of the ice crystals that had formed, flash freezing was born.
Today blast freezers use this concept on a commercial level and replicate the process by circulating very cold air, typically between -10oF and -20oF, over pallets of products at a high velocity. This method promotes rapid freezing. The fast freezing process means water freezes more quickly, reducing the size of the ice crystals that form and maintaining the product’s integrity - ideal for manufacturers and end consumers. Product that’s subject to blast freezing is then moved to conventional freezer storage.
An Americold Blast Freezing Cell
In 2020, Americold blast froze 4.8 billion pounds of product at more than 75 facilities around the world. Check out our blast freezing facilities.
Blast Freezing as a Science
Because blast freezing is energy intensive, it makes sense to maximize process efficiency when and where you can. For Americold, that means optimizing each blast freeze cycle based on product type, ensuring proper case and spreader slat placement, and running the blast freezer cells only when full.
Time in the blast freezer varies depending on product type, case size, and packaging. Americold works closely with food producers who require blast freezing and adheres to all government regulations regarding temperature blast times, monitoring and reporting.
Beyond that, for stationary blast freezing, opportunities to maximize efficiency lie within three primary areas:
Product loading & positioning: Product must be loaded onto pallets and then specifically arranged or configured into the blast freezer cell in order to optimize air flow on and around the product. If product is too close together, air flow will be obstructed and freeze times will be longer which could lead to larger ice crystals and a breakdown of the product’s integrity. If product is too far apart product will freeze more quickly but at the cost of wasted energy – more product could have been blast frozen for the same amount of energy usage.
Air flow: The velocity of the air being passed over the product should be equal throughout the room to ensure uniform freezing. Pallet spacers create air flow channels that ensure cold air has contact with multiple sides of each case of product, promoting ideal freezing conditions. This, along with proper evaporator function (air handling), optimizes freeze time and energy use.
Refrigeration system design & operation: A well designed refrigeration system should have the condenser capacity necessary to easily maintain the lowest required temperatures throughout the cold storage facility during both expected peak system usage and the warmest months of the year. The condenser’s efficiency is enhanced with a quality evaporator unit with optimized refrigeration fin surface area and spacing. This reduces stress on the entire refrigeration system by minimizing the temperature difference requirement (TD) necessary for effective heat transfer. These design features allow for efficient operation by minimizing the pressure difference between the lower and upper system pressures, also known as “compressor lift.”
Americold Associates prepare layers of product with spreaders in between to aid in the freezing process
At Americold, we strive to optimize all our processes, including blast freezing, to maintain responsible energy consumption levels for the work that we do in the communities in which we operate. Our blast freezing services provide the ability for producers and distributors to deliver harvest-fresh products to their customers.