Tech Update: Cooking and frying
Old fashioned high volume

May 3, 2007
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Processors insist on maintaining product attributes when evaluating new cooking systems. New technology meets old needs while boosting yield and throughput.

From breaded patties to whole chickens, demand for heat-and-serve meats is booming, prompting food manufacturers to demand cooking systems that can boost throughput while maintaining product consistency and quality. Source: FMC FoodTech.


Change is exciting and scary, and both emotions play out when food processors consider new-generation cooking and frying systems: higher throughput and yield are appealing possibilities, but if taste, texture, color or appearance is affected, the outcome is frightening.

Product diversity is the wild card in the mix. Products that reflect ethnic tastes, serve convenience demands and can help stake out a healthier-eating claim require production lines with greater flexibility. The challenge for suppliers is to leverage the principles of heat transfer to engineer systems that can produce new items while still doing justice to the old.

Nowhere is this more evident than with contemporary ovens. Heat-and-serve meat and poultry products are enjoying bullish growth, spurring continuous innovation in the pilot plants of equipment suppliers. Researchers at University of California-Davis utilized computational fluid dynamics (CFD) in designing a new spiral oven with a circular enclosure for Hayward, CA-based Heat and Control Inc. Dead zones in square configurations were eliminated with a 360

The tortilla has emerged as a global food wrap, and US oven fabricators are maintaining their technology lead with innovations such as the Odyssey oven’s diagonal burner array. Source: Casa Herrera Inc.

Sidestepping an oil crisis

Banishment of trans fats sounds the death knell for partially hydrogenated fats. While that’s good news for human health, “zero trans-fat oils break down more easily,” points out FMC’s Gunawardena. As a result, “continuous filtration is a must in a frying system,” and the more fines that can be removed, the better. The new-generation centrifugal filtration system for his firm’s fryers traps particles as small as 5 microns, five times smaller than the prior generation filters.

A double filtration system supports Heat & Control’s oil-curtain fryers, says Kozenski. Coarse particles down to about 200 microns are removed in a drum style or motorized mesh box, followed by filtration through stainless-steel mesh or a centrifugal press using paper or cloth media. “You can filter down to a single micron,” he says. Continuous filtration enabled Kar’s Nuts Co. to reduce oil use 35 percent and achieve a more even roast, compared to the direct gas-fired roaster it replaced, according to Kar’s Bill Elam (see story on page 70).

Used in conjunction with magnesium silicate to encapsulate free fatty acids, advanced filtration can dramatically cut down the amount of oil waste from a food fryer. The other key factor impacting oil maintenance is the turnover rate, the operating time in which all the system’s oil would be absorbed if no replenishment was done. “We target eight hours for turnover,” Kozenski says.

Besides submersion fryers, Heat and Control fabricates a unit marketed as HeatWave that slashes oil demand by using a series of oil curtains to fry foods. Continuous pellet-snack frying is the newest application, following breaded meats and nuts. Donuts are “something we’ve been playing with,” Kozenski says, though flat products with large diameters tend to exhibit color differences because steam and moisture can insulate the product’s underside. “We’re not averse to trying it on anything,” he says, “but we’ve learned there are things it doesn’t do well.”



The addition of an impingement zone at the back end of the Gyrocompact II oven provides significant flexibility in achieving different color and appearance without sacrificing yield. Source: FMC FoodTech.

Weirs above a conveyor divert oil into two thin curtains of oil from each weir, increasing the oil’s exposed surface area but not to the point that rapid oxidation occurs. Surface tension on the product helps the oil flow to the underside. For small products like nuts and pellet snacks, even color is achieved, even with multiple product layers.    

Two-stage filtration also is used in FMC FoodTech’s TFF-IV fryer. Coarse particles are trapped by a sediment conveyor belt that runs counter to the product’s path. Finer particles such as suspended flour are removed with a centrifugal filtration system. System improvements to control oxidation also have been made, according to Gunawardena.

The units typically are used to par fry product for 30 seconds before it is cooked. The heat exchanger’s electro-polished fins in a vertical array keep the build-up of free fatty acids to a minimum to extend oil life, particularly for less stable non-trans fat oils, he adds.



A circular enclosure around Heat and Control’s spiral oven helps promote 360º airflow up through the heat exchangers and down the sides to the racks, resulting in even heat distribution. Source: Heat & Control Inc.

Fry me, big boy

Few fryers can match the dimensions of units employed by North America’s largest potato processors to produce par-fried French fries for fast-food accounts. Throughput rates exceeding 50,000 lbs. an hour are possible in the largest units, and CFD has been used to engineer continuous systems that keep oil volume to a minimum. Controls have become highly sophisticated, though in some cases suppliers are hard pressed to keep up with innovations in the plant.

Nine years ago, GEM Equipment of Oregon Inc. began working on a recipe management system to regulate actuators for inflow and discharge of oil, optimize distribution from the heat exchanger and control fryer pumps, recalls Ed McKenney, president and cofounder of Woodburn, OR-based GEM. “It was a good system, but our timing was awful” when it was introduced two years ago, he says. Plant-wide controls architectures that could manage all the equipment were being put into place. “We missed the window,” says McKenney.

The company’s engineers didn’t miss the window on oil-volume control, however. GEM dominates the fryer segment with belt widths of 7 ft. and greater, McKenney boasts, and mastery of CFD to reduce oil volume has been a key to its success. Retooling existing fryers accounts for most of the firm’s work today. “With flow modeling, we almost always can improve the flow rate of a fryer,” he says.

A wire mesh belt with a center support and outside return conveys fries through a shallow oil pan in the firm’s fryers. The faster the oil flows through the fryer, the more rapid the heat transfer to the product. Flow causes turbulence, and when GEM began fabricating fryers 22 years ago, a series of humps prevented individual pieces from moving through the fry zone too quickly. With better understanding of forces such as the specific gravity of the potatoes vs. the oil and the friction between product and the belt, engineers have been able to eliminate humps in the design.

Many incremental improvements add up to greater control and repeatability in cooking and frying systems. They also give food processors confidence they not only can maintain consistency in their mainstay products but also tackle foods formulated to meet new consumer demands.


For more information:

Seth Pulsfus, Alkar-RapidPak Inc., 608-881-5234, seth.pulsfus@alkar.com

Wes Lowery, Casa Herrera Inc., 909-392-3930

Ramesh Gunawardena, FMC FoodTech, 419-626-0304, ramesh.gunawardena@fmcti.com

Ed McKenney, GEM Equipment of Oregon Inc., 503-982-9902

Doug Kozenski, Heat and Control Inc., 847-395-6478, dougk@heatandcontrol.com

The control panel for the oil-curtain fryers at Kar's Nuts in suburban Detroit takes the guesswork out of production while improving product quality and reducing oil waste.

Sidebar: Thin film gets two thumbs up

Managers at Madison Heights, MI-based Kar’s Nuts Co. found themselves in the early-adopter role two years ago when production began on two new roasters which recently had made their debut in a roasted nut role after years of starring in heat-and-serve meat and poultry productions.  Two of them had visited Heat and Control’s Hayward, CA, facilities in mid-2003 when the first HeatWave reengineered for nut roasting was completing production trials. After confirming the fryer would roast the top and bottom of nuts evenly, they ordered two of the units for their new plant, which began production in January 2005.

Instead of submerging nuts in oil, the fryers rely on a series of oil curtains, thin films created when oil falls over a weir, to fry the product. The system requires significantly less oil, and continuous filtration extends useful life.

 “You’re always looking for savings wherever you can find them, and the HeatWave system has reduced the amount of oil we have to discard to almost nothing,” says Kar’s Bill Elam. “But the biggest benefit was the improvement in terms of quality and consistency of our nuts.”

Each fryer has a capacity of 7,000 lbs. an hour, double the combined throughput possible on the company’s old roasters. Until sales catch up with capacity, roasting is done only part of the time, with an 8,000-gal. storage tank maintaining the oil’s integrity when the line is down.  When manufacturers stretch out production to fill a shift, “they run into trouble” by causing the oil to degrade, cautions Heat and Control’s Doug Kozenski. If a fryer runs at less than its rated throughput, turnover is negatively impacted, he notes.

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