Low pH and water activity make many food products shelf stable, and commercial sterilization and packaging allow other foods to be handled at ambient temperatures. For everything else, refrigeration is necessary for preservation, and food processors can choose from a number of options to address cost, throughput and quality considerations.
Options are needed, too, as industry reacts to spiking prices for R-22 refrigerant. Because of its contribution to global warming, this hydrochlorofluorocarbon is being phased out, and prices are surging as supplies dwindle. At $15 a pound, recharging a mid-sized industrial refrigeration system of 30,000 lbs. now costs $450,000, calculates Don Stroud, a senior engineer with Stellar Inc., Jacksonville, Fla. By contrast, a similarly sized ammonia system would cost $30,000 to recharge.
Stroud, a former corporate engineer with Kraft’s Oscar Mayer division, advises food companies who are expanding or replacing refrigeration systems that rely on R-22 to give serious consideration to switching to ammonia, which is “very efficient, environmentally friendly and a natural refrigerant.”
In fact, most food companies already have made the transition. Lingering safety concerns keep some food companies from installing ammonia systems, but the overwhelming majority of Sterling Industrial Refrigeration’s mechanical installations are ammonia, with perhaps 5 percent opting for Freon, estimates Rich Matrunick, project engineer at the Morrisville, N.C., firm.
Another deterrent to anhydrous ammonia use are state regulations, with particularly tight controls in California and New Jersey, where Sterling is bidding a cascade system that would restrict ammonia to the engine room, where it would chill a carbon dioxide loop that runs through processing and storage areas.
Alternatives other than ammonia exist for R-22, but neither engineer considers them efficacious. None of them performs as well as R-22, believes Matrunick, and Stroud points out they typically are a blend of two or three refrigerants. When a leak occurs, “You leak more of one than the others, and then you lose the characteristics of the blend” if the system is topped off. To ensure the desired characteristics are retained, a complete recharge often is necessary.
CO2 and ammonia may become the dominant refrigerants in mechanical systems. For cryogenic freezing, liquid CO2 and nitrogen are the refrigerants of choice. Processors are gaining greater flexibility in which refrigerant to use, depending on gas costs in their location.
An example is a bottom-injection system from Linde North America that can use either liquid nitrogen or carbon dioxide. Following a successful beta test at Interstate Meat Distributors Inc. in Clackamas, Ore., Linde introduced the versatile system at January’s International Production & Processing Expo in Atlanta.
The two-gas option is Linde’s latest refinement in bottom injection for mixers and blenders, explains Mark DiMaggio, head of food and beverage for Linde, Murray Hill, N.J. Known as the Accu-Chill, the system overcomes the inherent inefficiency of top-loading of a cryogen.
“We asked, ‘Why are we allowing the cryogen to go through an air medium and lose refrigeration potential?’” DiMaggio recalls. “It’s much easier to put a snow cone on the top of a mixer, but from an empirical standpoint, you get out a lot more BTUs with bottom injection.”
The firm works with several manufacturers of mixers and blenders to engineer bottom injection when machines are fabricated. It also retrofits machines already in the field. With a ribbon blender, workers might weld 10 nozzles on either side of the tank, replacing three or four top-loading cones. When combined with a weighing system that factors in the fat:lean ratio in a batch, bottom injection can result in 5-15 percent lower operating costs and faster cycle times, according to DiMaggio.
In the case of Interstate Meat, cycle times for ground beef destined for patty forming shrank to three minutes from eight, the company reports, a savings that not only boosted throughput but also produced less emulsification of the fat content, resulting in a more attractive patty.
Calling the Accu-Chill “the hottest product we’ve got,” DiMaggio says the system chills “not only more efficiently but also more accurately” than top-mounted injection. The best scenario is integration of the cryogen nozzles when the mixer or blender is built.
Integration of refrigeration during machine fabrication usually results in better performance, a fact not lost on managers at Provisur Technologies Inc., the Chicago-based consortium that numbers Formax among its forming, slicing and grinding brands. The firm recently formed a partnership with Scanico A/S, an Aalborg, Denmark, specialist in commercial freezing technology.
Precise temperature control is critical when meat, poultry, seafood and other proteins are delivered to a forming machine, and Provisur hoped to add that competency three years ago when it acquired a Dutch firm.
“Behind every Formax, there must be a freezer,” says Lars Colding, Scanico managing director. Adds Brian Perkins, vice president of global product management, “Frankly, we were weak when customer discussions shifted to freezing.” By partnering with Scanico, Perkins believes the firm can engineer integrated systems that optimize performance and throughput.