Food Engineering

Tech Update: Cooking & Frying

March 1, 2011
Improved energy efficiency, fun shapes, healthier eating: myriad market demands are driving changes in commercial cooking and frying systems.

Growing popularity of sous-vide meats is a boon for Wolf-tec’s water-emersion cookers and chillers. Molded meats and deli logs measuring 10 ft. or longer are automatically conveyed in and out of the systems, allowing processors to attain throughputs of 330,000 lbs. a day. Source: Armor Inox.


Processors can apply grill marks to one or both sides of formed and natural products with Heat and Control’s Rotary Brander. Source: Heat and Control.

In the 20th century, thermal workhorses such as cooking and frying systems were judged on gross throughput. In the 21st century, other factors come into play. Overall equipment efficiency forces food manufacturers to consider changeover time and product waste and rework. Rising energy costs bring operating efficiency into the equation. But perhaps the greatest influence is the change in people’s consumption patterns: Whether driven by whim or the trend toward healthier foods, those demands require manufacturers to consider versatility, flexibility and modified outcomes when evaluating equipment options. Integration of vacuum to both cooking and frying systems is a case in point.

Scientific evidence is mounting that vacuum frying results in less oil pickup in potato chips and novel vegetable and fruit chips than conventional frying. In the January edition of the Journal of Food Science, researchers reported vacuum-fried carrot and potato chips absorb half as much oil, compared to those produced via atmospheric frying. A less dramatic 25 percent reduction in oil pickup was observed with apple chips. Earlier studies have noted that vacuum frying allows a reduction in oil temperatures.

Fry shortening prices are up more than 50 percent in the last year, and additional price shocks are anticipated. Technology that addresses human health concerns while lowering processing costs falls under the heading of win-win.

To date, vacuum frying has been a curiosity in the North American market, and the few applications involving commercial products have fallen flat. Deep fryers and conventional fryers are entrenched, and healthy snacking products have come and gone. But obesity concerns put the status quo in doubt, and January’s release of the new Dietary Guidelines for Americans from USDA and the Health and Human Services department will nudge change along. Snack food manufacturers have modified product formulations in recent years to deliver healthier products with reduced sodium, sugar and fat. New equipment also is coming into play. An example is a heated de-oiling centrifuge that Hayward, CA-based Heat and Control Inc. developed for use with batch fryers. The centrifuge removes one-quarter to a third of the surface oil residing on chips as they exit the fryer, reports Doug Kozenski, sales manager-processing systems.

Less oil pickup isn’t the only health benefit with vacuum frying, however. Lower operating temperatures eliminate the formation of acrylamide, the possibly carcinogenic chemical compound that forms when sugars and the amino acid asparagine found in starchy foods are subjected to high-temperature cooking. “We fry at 120°-125°C (248°-257°F) instead of 180°C (356°F), so there is no caramelization of the sugars,” explains Marcel Kloesmeijer, commercial director of BMA Nederland BV in Woerden, the Netherlands. His firm’s Florigo unit began supplying vacuum fryers in the 1960s, when poor potato crops forced European snack manufacturers to try alternative technologies to prevent discolored chips. Vacuum frying languished as a niche technology until health concerns renewed interest in it. Several US food companies now use vacuum fryers for their European snack products. Tokyo-based Calbee Foods Co. uses more than a dozen units to produce Jagabee potato sticks, a healthy snack that has attracted a huge following since its introduction in 2006.

Major US fryer suppliers have not developed vacuum systems. Reduced oil pickup comes at the expense of greater water loss, points out Ramesh Gunawardena, manager-technology & process development at JBT FoodTech, Sandusky, OH. “If you sell by weight, yield comes into play,” he cautions. “It all depends on how companies value the product.” JBT’s research and development focuses on continuous fryers.

Because frying occurs in a vacuum tube, vacuum frying essentially is a batch process, a fact that limits throughput. Even the largest units, which measure 40 ft. long and 10 ft. in width, can only produce about 660 lbs. of product an hour, says Kloesmeijer. And the units are expensive. But last year, PepsiCo secured a patent for a process that incorporates a pre-fryer that can push production to 3,000 lbs. an hour. PepsiCo’s patent covers the temperature profile in a multi-stage process. BMA holds the patent on the fryer itself, and the two companies are now “linked at the hip” and will soon join forces in a promotional effort, Kloesmeijer says.

Some searing occurs when meat and poultry pass through a grill-mark unit, but the main affect is aesthetic. Catering to diners’ desire for food that looks as good as it tastes is driving widespread installations of such equipment.

Advances in IR

Vacuum cooking has followed an easier technology-adoption curve, and Santa Rosa, CA-based Blentech Corp. has augmented it with kettles that also offer vacuum chilling. The technology can’t compete with scraped surface heat exchangers when consistent commodity cooling with large volumes is the goal, allows Daniel Voit, vice president & chief operating officer, but “when batch processing high-end soups, sauces and slurries, vacuum chilling becomes more attractive.”

Blentech’s cook/chill vacuum technology was widely adopted in the UK market when refrigerated ready meals became a supermarket sensation. “Quality was number one on the minds of a lot of our UK customers, and they gravitated to this,” says Voit. Problems with violent boiling while chilling with vacuum were addressed with improved controls technology, but vacuum cooling is a relatively slow process. Blentech addressed this by using the kettle’s double-walled jacket to both heat and cool. Assuming 40°F water is used, the jacket accelerates product cooling down to 104°, at which point the vacuum system kicks in.

Engineering innovations in oven design that significantly reduce energy consumption are being brought to market by Souhel Khanania, president of Coppell, TX-based IET Combustion LLC. Khanania designed an oven for Shearer’s Foods’ Massillon, OH plant that lowered energy inputs 40 percent, compared to conventional ovens. A well-insulated frame that restricts air inflow by about two-thirds accounts for part of the savings, but Khanania’s infrared burners added a higher level of technical innovation.

Metal matrix emitters replaced ceramic emitter faces in food applications of infrared burners because of the risk of glass contamination and higher maintenance requirements. IR burners with a metal matrix face address those issues, but Khanania says the surface of the burners have operating temperatures approaching 2,000°F. “Metal oxidizes in a matter of months, and the higher the temperature, the faster the deterioration,” he says. His solution combines a convection component with infrared. “The hotter you fire it, the longer it lasts,” Khanania boasts. “There’s nothing like it in the world.” His engineering team is adopting the burners for fryer applications.

Conventional ovens rely on the convection effect of outside air to dry product, but that cooler air must be heated. “The stack has this enormous draft, and you create suction and a cooling effect,” he explains. Khanania’s burner already has a convection component, negating the need to draw in cooler air. “The only thing we want to exhaust is the energy through the burners,” he says. Khanania estimates his firm has retrofitted almost 200 ovens for PepsiCo, but the Shearer’s project gave him a clean slate to apply his burners and resulted in significantly greater efficiency.

A worker performs a QA check on seasoned sweet potatoes with a temperature probe as product exits an AirForce oven. Source: Heat and Control Inc.

Technology transfer

Silo syndrome can prevent processors in one segment of food production from reaping the benefits of technical advances in another. That is especially true for fryers: Bakery units have not received the research and development focus that was poured into units designed for meat, poultry and snack foods. Fortunately, change is occurring.

The process began a few years ago when Heat and Control built a 36 ft.-long donut fryer with a 40 in.-wide belt. The dimensions were “outside the comfort zone” of most donut fryer manufacturers, says Kozenski. Heat and Control’s expertise in zone control, temperature control and other engineering issues in meat and poultry frying helped ease the transition to baking applications.

As attendees at September’s IBIE baking show in Las Vegas discovered, another meat-frying expert also is getting involved in donut frying. Seattle’s Belshaw Adamatic has partnered with JBT FoodTech to fabricate fryers up to 40 ft. long. More significantly, the larger units incorporate advances JBT FoodTech developed for protein frying. Commercial availability is expected this summer.

The collaboration is expected to yield both quantitative and qualitative improvements. Electro-polished heat exchanger fins resist sediment sticking, resulting in less temperature differential and oil breakdown. Centrifugal filtration will effectively remove starch from the bottom of the fryer, reducing oil degradation. And while conventional donut fryers have combustion efficiencies of about 60 percent, the hybrid unit is expected to operate at greater than 80 percent efficiency.

People want food that not only tastes good but also looks appealing. Some flavor enhancement, but mostly surface-color development, is added when infrared burners are included in a cook line to create grill marks on meat and poultry. Grill marks also can be added with “floating rings” that follow the contours of the meat as it is conveyed, says Kozenski. That’s the approach taken with Heat and Control’s “rotary brander,” a machine that heats metal rings to temperatures of 1,100°F or greater. With formed products, fixed bars create the grill marks.

La joie de sous-vide

Nothing says high-volume and automated production like the cook/cool/chill water emersion systems manufactured by Wolf-tec Inc., a Kingston, NY division of Armor Inox. Applied primarily to molded meats such as deli logs and hams, the system combines an age-old cooking process with advanced material handling. Two operators on two shifts can produce 300,000 lbs. of finished goods a day, according to Josef Rohrmeier, Wolf-tec product manager.

Water bath is riding the crest of sous-vide (under vacuum), the French culinary method that requires precise temperature control over extended periods as food is cooked in airtight plastic bags. Sous-vide’s roots are in the 18th century, but the methodology was impractical for commercial purposes until precise temperature controls could be applied. Inexpensive PID controllers have brought sous-vide into home kitchens, but the precision of the heat application also makes it a favorite of top chefs and foodservice operations.

Just as steam cooking is much more precise than hot air, water cooking is a quantum improvement over steam. Rohrmeier says water temperatures vary less than 1°. With steam, 3°-5° variances from set point occur. Tighter tolerances also result in uniform color.

When complex flavor profiles are desired, water bath isn’t an option. Surface coloration can be added by coating the inside of plastic wrappers with chemicals, though the penetration is less than 2mm, Rohrmeier says. On the plus side, a wide range of smoke flavors can be imparted with the film. “You no longer need a smokehouse,” he says.

Because water never contacts the meat, fish or other product being cooked, the water can be filtered and recirculated continuously. Wolf-tec’s largest systems employ three heat exchangers as the cook/chill cycle is repeated for each batch. All steps occur in the same tank. “It’s more economical to pump water in and out of the same tank than to transfer 15,000 lb. batches of product,” Rohrmeier points out.  

While the process has remained essentially the same for decades, new wrinkles continue to be added. The customized molds that hold Virginia hams and turkey breasts often are used to create a netting effect on molded meat without using actual nets. Molds built for Disneyland Paris are creating ham sandwiches with the profile of Mickey Mouse: a head and two ears. 

If energy efficiency was the only consideration, water baths would cook all meats. But energy use is only one of many criteria, just as throughput is a single consideration. Whether the objective is healthier foods, funky shapes or some other goal, cooking and frying technology is being modified and improved to deliver the desired results. 


For more information:
Daniel Voit, Blentech Corp., 707-523-5949, dvoit@blentech.com
Marcel Kloesmeijer, BMA Nederland BV, 31-348 435 490, mkloesmeijer@bma-nl.com
Ramesh Gunawardena, JBT FoodTech, 419-626-0304, ramesh.gunawardena@jbtc.com
Doug Kozenski, Heat and Control Inc., 847-395-6478, dougk@heatandcontrol.com
Souhel Khanania, IET Combustion LLC, 847-946-5578, souhel@ietcombustion.com
Josef Rohrmeier, Wolf-tec Inc., 845-340-9727, jrohrmeier@wolf-tec.com