Design Improvements Help Lock In Moisture And Protect Flash-Frozen Foods

Regardless of the refrigerant used, freezing systems are taking a bigger role in producing superior products while preserving as much floor space as possible.

By Kevin T. Higgins, Managing Editor

Product preservation is the primary mission of refrigeration, and for perishable food and beverage products, it’s a necessary cost of doing business.

Efficiency is important, but it’s not the only metric companies consider. When flash freezing is the application, product quality in general and moisture retention in particular is important.

An IQF contact freezer from Akranes, Iceland-based Skaginn 3X (www.skaginn3X.com) has enjoyed success with individually quick frozen seafood and poultry products since it was introduced, with approximately 60 installations worldwide.

Scallops are a particular sweet spot: Moisture loss as low as 0.2 percent has been achieved, a factor in the decision by the U.S.’s largest scallop processor to commission a unit with a capacity of 9,000 lbs. per hour. Atlantic Capes Fisheries Inc., which processes 22 percent of landed scallops from its 17 sea vessels, is operating the system at its Fall River, Mass., facility.

Mechanical freezing with ammonia or Freon-type coolants was the usual method with the earlier freezers, according to Sigurdur Skulason, regional sales manager, although Atlantic Capes uses carbon dioxide to achieve flash freezing temperatures of -58°F. Extreme cold isn’t the freezer’s distinction, however: Rapid crusting in a low air-velocity chamber is the key to locking in moisture prior to freezing items to their core.

Unlike most cryogenic freezers that use liquid nitrogen, “It’s a closed loop, so you’re not spreading gas into the environment” and driving up costs, Skulason explains. A flat modular belt can be used to convey product, but Skaginn’s proprietary Teflon-coated aluminum droplet belt accelerates crusting.

“We are crusting the product in 3-5 minutes,” he says. “On a regular belt, it takes 10-15 minutes to crust. By minimizing the amount of air hitting the product, you maximize yield.”

Crusting of surfaces that did not adhere to the belt occurs in this still-air zone. When the belt reaches its turning point, the outside of each item is fully crusted, and the area in contact with the belt has shrunk slightly, allowing it to break free of the belt and be deposited onto a lower belt, where high-velocity air blasts it.

Compact design is part of the system’s appeal, Skulason notes, and the footprint can be further reduced by locating the freezer itself outside the processing building, as was done at Atlantic Capes. Loading and unloading is done indoors.

Coils are designed to minimize ice buildup. Some food companies operate the freezer up to six days between defrosting and cleaning cycles, he says. Coupled with faster freezing, the result is less downtime and higher throughput.

Given Skaginn’s Iceland roots, it’s logical that seafood would account for a significant proportion of installations. IQF poultry applications also are well represented. Besides installations at chicken companies in Brazil and Chile, half a dozen units are installed at Tyson Foods facilities.

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Little feet

Compact design also is a benefit in Linde North America Inc.’s (www.lindefood.com) latest IQF freezing advancement. The Bridgewater, N.J., vendor introduced at IPPE Expo an agitation feature for its cryogenic impingement freezer that cuts floor space in half for the same throughput, according to Mark DiMaggio, head of applications and marketing.

A series of cams, spaced about 14 inches apart, are under the conveyor’s wire belt. They produce a roller-coaster effect and propel products airborne to expose all surface areas to high-velocity, -320°F air for faster heat transfer from the product core. The result is less dehydration and higher yields.

“This innovative design optimizes both the physical motion of products and the flow of cryogen through the freezer,” says DiMaggio, “and packs that technology into one compact unit.”

Phillips Mushroom Farms, a Kennett Square, Pa., grower of specialty mushrooms, served as the beta site for the wave-impingement freezer in a six-month shakedown application.

Cryogenic freezing on a micro-scale is being served by two suppliers, the latest being Dippin’ Dots Cryogenics LLC, a new business unit of the Paducah, Ky., maker of beaded ice cream treats.

Founded 30 years ago, the frozen novelties company vigorously defended its 17 U.S. patents for cryogenic freezing until the patent office voided them in 2007. Ownership changed in bankruptcy court in 2012, and Dippin’ Dots announced in January that it will make the equipment and intellectual property for its process available for licensing and sale.

The new venture will compete directly with Praxair Technology Inc., which introduced at IPPE 2017 a pellet and dot freezing system for sauces, purees and ice cream. For ice cream, a slip stream diverts about 10 percent of flow to a liquid-nitrogen bath, where immersion creates 3-4mm spheres that are then returned to product flow. The advantage is reduced load on the mechanical refrigeration system.

Stan Jones, chief technology officer at Dippin’ Dots (dippindots.com), says the key distinction with his system is throughput. “We can do a tremendous volume in a very small footprint,” says Jones.

He describes Dippin’ Dots’ approach as a “funnel-hopper type system,” with liquid droplets falling into a liquid nitrogen bath and quickly extracted in solid form through a screw conveyor. Ice cream spheres are typically 4mm. Different sizes can be formed, although tight tolerances demanded by some potential end-users are driving some fine-tuning of the process.

According to Jones, several systems have been commissioned and more are in the pipeline. Yogurt manufacturers are early adopters, applying the technology to starter cultures that are then freeze dried. Flash freezing is a safeguard against contamination prior to freeze drying and helps dairy processors meet growing demand without additional production lines.

Safeguarding against contamination is attractive to other products and processes, including probiotics and cheese. Pharmaceuticals likely will account for an outsized portion of early adopters. Dippin’ Dots made its trade show debut at June’s Bio International Convention in Boston.

The technology’s potential in food production is still coming into focus. “If pelletized meat was flash frozen, this technology could help in portion control,” Jones suggests.

Besides a compact footprint, the system is low maintenance. There is only one moving part, he says, and four of the company’s units have been in production for 20 years.

Managing cost of production and storage has made ammonia-based mechanical freezing the go-to freezing option in food, although cryogenic freezing continues to make inroads with value-added products. Regardless of the refrigerant used, freezing systems that lock in moisture and safeguard products from contamination meet a growing need for manufacturers intent on escaping commodity pricing and delivering superior products.

If their design is compact, so much the better.

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