Linde's hygienically designed cryogenic injector for chilling mixers and blenders can be used with liquid nitrogen or CO2. 

Solid results

Processors are using CO2 in different ways, as suppliers have developed and enhanced technologies for product quality and safety as well as operational benefits, such as cost savings, employee training and efficiencies.

Quality is a priority for chilling. “Processors require rapid chilling of products to cool them quickly to a maintenance temperature for handling, shipping and further processing. Automated and precise delivery of carbon dioxide snow ensures no hot or cold spots which, when present, may translate into re-work. Maintaining low temperature preserves product quality and greatly reduces bacterial growth and resulting spoilage that would negatively impact the product,” Davis says. Praxair produces carbon dioxide snow from pressurized liquid as it is released through snow horns, a process that may be monitored and maintained electronically.

DiMaggio points to some employee-related benefits of today’s CO2 chilling systems compared to traditional ice or CO2 dry ice. “The utilization of pellets is associated with labor-intensive applications in which they’re loading pellets into boxes, combo bins, mixers and augers. But employees don’t have any real accurate method of adding pellets for consistency. So ultimately, the temperature profiles vary within the box and from box to box,” he explains. Adding, “Safety is also an issue when using pellets, because it’s challenging to maintain OSHA’s long-term and short-term exposure to CO2.”

Loss is part of the equation, too. In using CO2 pellets, the process of sublimation changes solids directly into a gas. “Pellets begin sublimating immediately after they are manufactured. While sitting in coolers ready to use, and then when you open bins on the plant floor, you increase the rate of sublimation. Losses are typically 15 to 20 percent with pellets, so the cost you are actually paying to chill is much higher,” DiMaggio says.

Using carbon dioxide snow to remove heat cools a variety of products effectively, including chicken patties.
To alleviate challenges in certain parts of the process, chilling system providers offer new automated solutions. Linde offers an automated box chiller that generates CO2 snow “on demand” and deposits it directly into open packing boxes as they move along a conveyor.

“The chiller installs in line with the current conveyor line. When it ‘sees’ the box, it automatically initiates a cycle of CO2 snow in a consistent amount that we calibrate to reach a final desired temperature,” DiMaggio explains.

Even with advances in automated snowers, pellets still have their place, including in plants that may not need automation. “Pellets are also produced by Praxair for operations requiring cooling in areas throughout the production and are often added by manual addition,” Davis says.

Meanwhile, other cryogenic chilling systems have been the focus of improvement, including chilling in combo bins. Praxair uses PLC controls to add carbon dioxide snow through an even-chill system for bulk product chilling. “The computer control system is programmed to balance the weight of the product and bin in order to calculate the exact amount of carbon dioxide snow needed to reach a pre-determined target temperature. The system allows even layering of product and snow to ensure a thorough and uniform chill,” Davis says.

Recently, Linde launched hygienically-designed cryogenic injectors (called LIXshooter) for chilling mixers and blenders, which can be used with liquid nitrogen or CO2. “The LIXshooter design not only provides higher reliability, but important aspects of food safety. The injectors only open when there is pressure from the CO2 or nitrogen to eliminate the entrapment of any food product or moisture in the nozzle orifice,” DiMaggio explains. In addition, a dual-cryogen option makes it possible to switch between liquid nitrogen and CO2 in a matter of minutes, he says.

“For liquid products, Praxair has worked with processors that need cooked, pumpable liquid foods cooled quickly,” Davis says. “For them, our in-line process uses liquid nitrogen added directly into the product pipe as it is pumped through the process to the holding tank.”