Rapid Chilling of Foods without Refrigeration
Any food processor in the business of making potato salad realizes that the only practical way to satisfy regional distribution requirements is to make a whole lot of product ― literally, thousands of pounds per hour. Only by using advanced cooking and chilling technology can a food processor ensure that the potato salad is fresh and delicious, and that it offers optimum shelf life without the use of preservatives.
Among the cooking systems suited for producing potato salad is a vacuum-sealed retort, a vessel used to cook diced potatoes within half an hour. The retort then chills the product to 35°F within just 17 minutes via an evaporative cooling system that does not use refrigeration.
“This type of system enables producers of fresh potato salads to cook and mix high volumes very quickly with equipment that requires a relatively small footprint compared to linear systems that require refrigeration or mechanical cooling,” says Carl Illiff, vice president of CMI Equipment & Engineering, Glencoe, Minn., a fabricator of specialized food processing equipment.
Illiff says that because the potatoes are cooled and chilled within a sealed retort, the food is not exposed to the air when being chilled as can occur with mechanical systems such as blast coolers.
“If the potato salad producer were to chill the diced potatoes in a blast cooler, it will take 18 to 20 hours to cool it,” he says. “And in the process, it will be exposed to bacteria, mold and yeast that are being circulated through these fans on the cooler.” When food is exposed to such biological organisms, shelf life is compromised unless the processor adds preservatives, something that consumers do not want to see on the labels of fresh foods.
A Purpose-Built Machine. The diced potato retort, which some food processors use to cook chickpeas and other vegetables, is designed by CMI as a complete package. The main part of the system ― a cylindrical chamber loaded with carts and trays ― is stainless steel and capable of a holding a vacuum. Normally, the retort is 12 to 22' long and about 5' in diameter, depending on customer specifications. Smaller models can cook and cool 2,000 lb of potatoes per hour; the largest ones can cook up to 8,000 lb per hour.
Contained inside an upper chamber in the retort are a shell-and-tube condenser and a liquid-ring vacuum pump that is, in turn, connected to a cooling tower. The shell-and-tube condenser provides evaporative cooling under high vacuum pressure created by the pump. Evaporated water is circulated from the condenser to the cooling tower and back to provide a continuous chilling effect.
A Purposefully Selected Cooling Tower. When you have 8,000 lb of potatoes steaming with heat, you need a reliable cooling system or you will end up with four tons of mashed potatoes.
When selecting the cooling tower to use the CMI's retort cooking system, “We were very concerned about the reliability, service requirements and lifespan of the cooling tower,” Illiff explains, "because our cooling system is dependent on it working correctly for a long period of time."
Illif selected a design that included a high-density polyethylene (HDPE) shell and enclosed direct-drive motor assembly manufactured by Delta Cooling Towers, Rockaway, N.J. Besides the HDPE shell design, Illiff cited Delta’s 15-year factory warranty as a reason to select the Delta cooling tower.
The shell-and-tube condenser provides evaporative cooling under high vacuum pressure created by the pump. Evaporated water is circulated from the condenser to the cooling tower and back to provide a continuous chilling effect.