Bakers demand more of their freezers, manufacturers respond
Industrial bakers are demanding freezers that offer reliability, extended run times, larger capacity and increased hygiene.
Many factors need to be addressed when purchasing a freezer. Bakers should start by considering the amount of time their product requires to freeze. Some freezer manufacturers use lab freezers to evaluate a product's freeze time. “The time requirement determines how big the freezer needs to be, and it can range from 15 min. to 60 min. or more,” says Chris Hanssen, freezer sales support and business development manager, FMC FoodTech Inc., Northfield, Minn.
In addition, bakers should consider the range of products they plan to run through each freezer and group similar products for maximum efficiency. Next, bakers must choose a belt speed that fits their capacity. “If running 200 pizzas per min., you need to be able to pull that product fast enough to prevent pile-ups, so that's where you get into fast belt speeds of 130 to 150 ft. per min,” Hanssen notes.
Bakers also should examine the plant space available, decide where the freezer out-feed will come from and check the vertical clearance needed for the product within the freezer.
The biggest decision may be whether to use a cryogenic freezer or a mechanical freezer, which dictates the type of refrigerant. Most mechanical freezing is done with ammonia. Plants located in strict zones, such as in a city, or near a school or residential area, might require a freon-type refrigerant. Some newer refrigeration systems use a CO2 cascade system, where CO2 is used for the low-side refrigerant and ammonia is used off the plant floor and kept in the engine room, Hanssen says.
Choose high quality
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Superior freezing and chilling
Bakers demand freezing, chilling, cooling and proofing equipment engineered for performance, flexibility, high volumes and safety. The innovative Northfield SuperTRAK® structure-supported spiral freezer from FMC FoodTech delivers on those needs, providing flexible configurations, different airflow options and a variety of belt types to optimize production and hygiene. Featuring a center drum drive system and patented F.A.S.T. sequential defrost, the SuperTRAK spiral helps processors achieve superior quality at a low total cost.
Processors are demanding wider freezer belts in the 54-in. to 60-in. wide range and faster belt speeds of 150 to 200 ft. per min. to handle increased capacities. “Downstream equipment, sheeting lines and laminating lines are becoming more efficient, so the freezers have to be able to keep up with that,” says Chris Hanssen, freezer sales support and business development manager, FMC FoodTech Inc., Northfield, Minn.
Sanitation also is a growing demand. Manufacturers who are running value-added products, such as pies, topped pizzas and cakes, are requesting more hygienic systems that allow for frequent cleaning.
In addition, more plastic and stainless steel belt options exist in a variety of strength ratings. “There are pros and cons to each belt, so you have to look at it on an application basis and take into mind customer preference,” Hanssen adds.
Operators also demand increased run times. One way to achieve this is using sequential defrost methods.
Freezer air circulates through a low temperature evaporator coil that has refrigerant running through it. After running for several hours, large amounts of frost accumulate on that evaporator coil because it is the coldest surface in the freezer. To keep running efficiently, bakers must defrost that coil. “The most basic system would run for the day, shut down, warm up the freezer and clean off the coil, but some bakers want to keep running for weeks,” Hanssen says.
To solve the problem, a sequential defrost system sections off the coils with sheeting for individual defrosting. This way three of the four coils can operate while one is defrosting. The refrigerant is shut off and hot gas refrigerant is run through the isolated coil followed by a water flush. “By oversizing the evaporator coil, you're not suffering a loss of capacity when one coil is down in defrost mode. You can keep up with the full demand and continue to run without any of the warm air migrating into the rest of the system.”
Different types of freezers
Both cryogenic and mechanical freezers offer benefits. Cryogenic freezers usually are tunnel freezers installed on the plant floor and piped to a remote tank supplying liquid CO2 or liquid nitrogen. The gas is injected into the tunnel, and fans circulate the gas. The operating temperature in a cryogenic freezer can be -80°F to -320°F, which is much colder than inside a mechanical freezer, which operates at -40°F.
“You mostly see cryogenic tunnels, but spiral freezers working on the same principle also are available,” Hanssen notes. “Cryogenic freezers allow for faster freezing and smaller equipment, but with bakery products, you also have to be careful as to how fast you freeze. You don't want to damage the yeast cells or cause crust flaking in your product by freezing too fast.” The benefit of a cryogenic freezer is lower capital costs initially because the equipment is smaller and easier to install than mechanical freezers.
In addition, gas companies often provide or lease the equipment because bakers will be buying their gas each month. Therefore, while operating costs are higher, the upfront cost may be lower. “Small processors that are getting started or have a smaller pilot line may want to consider cryogenic gas, but once a baker starts running medium to high capacities or operating more than five days a week, it can start to get expensive.”
Mechanical freezers have a closed loop refrigeration system and typically use ammonia as the refrigerant. The equipment sits on the plant floor and the refrigeration equipment resides in an engine room. “The cost of the cryogenic gas adds up with the higher capacities and longer run times, so that drives a lot of people to look at mechanical freezing for quicker payback,” Hanssen says.