Food Engineering

Two fronts in the cold-zone war

November 5, 2003
Food processors have two options in their efforts to boost efficiency and product quality from flash-freezing systems: invest in the latest technological advances, or simply learn to optimize the systems they already operate.

Ground beef exits a former enroute to Holten Meat’s cryogenic freezing tunnel. Source: Air Products and Chemicals Inc.

Holten Meat Inc., a Sauget, Ill., processor of hamburger patties, opted for the latter approach last year when management sought improved productivity from its liquid nitrogen freezing tunnels. After consulting with a needs assessment team from Air Products and Chemicals Inc., Holten began addressing operational issues with the cryogenic tunnels, such as improved maintenance of exhaust fans and other components, equipment updates and better reporting and management practices. The changes are expected to produce net savings of at least $1.5 million over three years, much of it coming from reduced nitrogen use.

Better QA management is another strategy many users of cryogenic freezing could benefit from, according to Air Products' Dietmar Gamm. Liquid nitrogen is a relatively expensive freezing option, and QA personnel need to be as diligent in dialing down nitrogen infeed as in dialing up. "The adjustments tend to always be made in one direction, and that is toward higher consumption of nitrogen," he says.

Processors who have adopted that approach and still are unsatisfied with the results might consider equipment advances, such as Air Products' new Z tunnel freezer. The unit uses indirect impingement freezing with nitrogen, employing heat exchangers and ducts. Heat transfer is approximately twice as high as with conventional cryogenic units, and response to variations in product load is much faster. Most systems don't react to changes in the amount of product being fed through until the food reaches a thermostatic control in the middle of the oven.

"If you have an ideally sized freezer, it's impossible to improve efficiency," Gamm says. "But there are no optimally sized freezer tunnels because of the constant shifts in load." That's where different technological approaches come into play.