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Potatoes and other foods chilled rapidly without refrigeration

Cooling towers ensure reliability of vacuum/retort cooking system that chills tons of ingredients per hour

March 01, 2013
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Because the potatoes are cooled and chilled within a sealed retort, the food is not explosed to the air when being chilled, such as occurs with mechanical systems like blast coolers.

In the potato salad-making business, one practical way to profitably maintain and grow regional distribution is to make a whole lot of product — literally thousands of pounds per hour.

It is also the case that today’s advanced cooking and chilling technology can ensure that potato salad is fresh and delicious, and offers optimum shelf life — without the use of unappealing preservatives.

Among the more sophisticated cooking systems appropriate for potato salad is the vacuum-sealed retort, a vessel used to cook diced potatoes within half an hour, and then chill the product to 35 F within just 17 minutes, through an evaporative cooling system that uses no 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,” explains Carl Illiff, a vice president with Glencoe, Minn.-based CMI Equipment & Engineering, a designer and 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 air while being chilled, such as occurs with mechanical systems such as a blast cooler.

“If the potato salad producer were to chill the diced potatoes in a blast cooler, it will take 18-20 hours to cool it,” he explains. “And in the process, it will be exposed to bacteria, mold and yeast that are being circulated through these fans on the cooler.”

Illiff adds that when food is exposed to such biological organisms, shelf life is compromised unless the processor adds preservatives, something that consumers don’t want to see on the labels of fresh foods.

Amazed reaction

The diced potato retort, which some food processors use to cook chickpeas and other vegetables, is designed as a complete package. The main part of the system, a cylindrical chamber loaded with carts and trays, is all stainless steel and capable of holding a vacuum of over 30 inches. The retort is normally between 12 and 22 feet long, and about 5 feet in diameter, depending on customer specifications. Smaller models can cook and cool 2,000 lbs. of potatoes per hour; the largest ones can cook up to 8,000 lbs. per hour.

Contained inside an upper chamber in the retort are a shell-and-tube condenser and a liquid-ring vacuum pump, which 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.

“This cooling process is amazing,” says Illiff. “When you remove the diced potatoes they are nice and cold, and ready to mix with the potato salad dressing, then package and ship to the customer — all with hardly any exposure to air.”

Illiff adds that because his equipment is meant to operate reliably for many years, he was especially particular when it came to sourcing the cooling tower that is integral to the cooking retort systems.

Evolved breed of cooling tower

When 8,000 pounds of potatoes are steaming with heat, nothing less than a reliable cooling system will do. Otherwise you’ll end up with four tons of mashed potatoes.

“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.”

In exploring available cooling options, he found that the majority of models were of the traditional, galvanized metal-clad design.

Eventually he found an alternative, a design that featured a high-density polyethylene (HDPE) shell and enclosed direct-drive motor assembly that promised to provide highly reliable operation with very low maintenance.

HDPE cooling tower shells are virtually impermeable to corrosive elements, including water treatment chemicals such as chlorine, as well as UV rays. “We found this HDPE cooling tower at Delta Cooling Towers, the manufacturer that originally developed the ‘plastic’ design, and has installed industrial, commercial and institutional systems nationwide since the 1970s.”

The HDPE shell design has a 15-year factory warranty, testimony to its lifespan and able to ensure the reliability of the retort-based cooking system. The cooling towers are available in a wide range of sizes from 10 up to 2,000 tons, but most typically in the 250- or 500-ton sizes.

“These cooling towers are also lighter in weight,” Illiff concludes.

The variable-speed, direct-drive motors that run the system fans also deliver benefits. Far more efficient than belt-driven or gear drives, the cooling tower design requires considerably less horsepower and therefore consumes less energy, providing some users up to a 50% savings in electric power.

For more information, contact Delta Cooling Towers, Inc., Rockaway, NJ 07866; Phone (800) BUY.DELTA (289.3358); Email: sales@deltacooling.com; or visit www.deltacooling.com.
 

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