Donuts are hot, hot, hot on the retail scene, with super-gourmet styles pushing $3 each. Could wholesale versions be far behind? And how about all those variety ingredients being added to snack foods? Whether or not such new product initiatives succeed, the need for quality products continues to change the configuration and operation of commercial-scale fryers and auxiliary equipment.

Premium ingredients shouldn’t present much of a challenge to modern frying systems. That applies as well to the ongoing transition out of partially hydrogenated oils into new-generation blends. Frying equipment manufacturers defer to oil suppliers to answer questions about oil performance and choice. “But it’s worth saying that no two customers are using exactly the same oils,” observed David Moline, sales and marketing manager, Moline Machinery LLC, Duluth, MN.

Consider, too, all the variety now showing up on snack food shelves. “We are seeing many new ingredients being added these days,” said Don Giles, director of sales, processing systems, Heat and Control, Inc., Hayward, CA. These materials range from jalapeño peppers to bean and soy flours and sesame seeds, which the industry refers to as inclusions.

“For the most part, this does not impact the operation of the fryer,” Mr. Giles observed, “however, sometimes they result in more fines, or particles, left in the fryer. This can increase the need for more oil filtration to prevent degradation of the cooking oil.”

Fryers have long been engineered to accept the product formulations their users require. “When a new product with new characteristics emerges, we can usually adapt by adding or altering components to suit the product,” said Irene Kimmerly, vice-president, sales, Belshaw Adamatic Bakery Group, Auburn, WA.

Click for a slideshow of high-quality fryers.

The process of adaptation starts with the customer, noted Ken Weekes, international sales manager and product manager, roll lines, WP Kemper, WP Bakery Group, Reitburg, Germany. “This is done within the adjustable parameters that we have available, such as dwell time and temperature in the fryer or proofer, as well as the position of the turning station in the fryer.”

Results of such work are worth the effort, according to Patricia Kennedy, president, WP Bakery Group USA, Shelton, CT. “The major challenge for all producers, from small bakery operations to large-scale snack food plants, is basically the same: how to introduce new or better products to the marketplace without increasing costs,” she said. “Standing out is key. The player that is there first sets the tone in the market.”

Observing the universals

Frying is different than other bakery and snack processing methods because the heat transfer medium — the hot oil — becomes part of the finished food. These foods cook by submersion in hot oil and through surface frying action. Cooking oils transfer heat efficiently. A product that takes four to six minutes to cook in a fryer might take 25 to 35 minutes in an oven.

Steady, consistent heating is even more important when frying than baking. Cook at too low a temperature, and the products absorb too much oil; too high, and they burn. Temperature control also affects oil ­quality. “If you can maintain low, steady-state heating, you minimize oil breakdown,” Mr. Moline said. “You need to maintain accurate temperature control with zone-based control.”

Because the quality of the finished product depends on the quality of the cooking medium, oil filtering can be an essential discipline for frying operations. Some products, donuts especially, absorb enough oil that replenishment normally will ensure optimum fat quality. Oils that fry most salted snacks, however, absolutely require filtering to remove the byproducts formed when the escaping moisture bubbles through the hot oil. And filtering is mandatory any time foods throw off fines.

Long an essential component of chip frying, filtering is getting more attention from donut processors. “Sediment removal and continuous filtering is essential when working with yeast-raised donuts or those containing fruit pieces,” Mr. Moline said. “These items come out of the proofer, or off the depositor, with starch or inclusions that can come loose and sink to the bottom of the fryer.”

Older fryers often had to be cleaned out once or twice a week to remove the accumulated fines and particles, but new designs equipped with automatic sediment removal and oil polishing can run continually for three to four weeks before needing a shutdown for cleaning.

Advancing the technology

Evaluating today’s choices in frying equipment, buyers will notice improvements in capacity and temperature controls as well as capacity increases.

Among mid-range systems, Belshaw Adamatic reworked its Century Donut System, Ms. Kimmerly explained. Fryers now extend to 14 ft long and output up to 10,000 pieces per hour, an increase of 40% over the previous capacity limit. The line uses PLC-based temperature controls coupled with modulating pre-mixed gas delivery systems “to smooth out temperature fluctuations and reduce overall energy consumption,” she said.

Physical changes also included conveyor hoists to facilitate cleaning, slide-in shortening ramps to simplify shortening insertions, faster speeds for turners and submerger swap-outs to save production time. Ms. Kimmerly said that taking such a “heavy duty” approach to construction enables usage approaching 24/7/365.

When Moline Machinery reengineered its fryers about four years ago, it developed the Libra design. “The Libra fryer is all about continuous sediment removal and rapid oil turnover,” Mr. Moline noted. This design also employs a lift system that permits separate handling of heating elements and conveyors to make the unit easier to maintain than the company’s earlier models.

For batch cooking of potato chips, Heat and Control raised capacity with its MasterTherm Kettle thermal fluid heated fryers that produce 500-plus finished lb per hour. Also new is the company’s Longitudinal Direct Kettle Fryer, capable of 200 to 300 finished lb per hour. Mr. Giles noted that these batch fryers incorporate PLC-controlled Chip-Stirr automatic slice agitation systems. Both designs of fryers feature a full-length hood enclosure with a motorized hoist, exhaust Oil Mist Eliminator and continuous fines removal.

And to produce variety products, the company’s range of continuous fryers readily handle nuts, pellets, tortilla chips and other snacks.

Fryer choice has also been altered by two changes among equipment suppliers. In one, Belshaw Adamatic Bakery Group partnered with JBT FoodTech, Sandusky, OH, to produce industrial donut fryers. In the other, WP Bakery Group added frying to its capabilities by acquiring Zeppelin’s frying equipment assets two years ago and using them to develop its Kemper high-volume, industrial donut line. In 2013, WP Bakery Group bought Riehle, a producer of frying systems, and is ­currently bringing its frying knowhow together.

The Belshaw-JBT project resulted in a high-volume fryer, which can be manufactured in lengths of 19 to 40 ft and capacities ranging from 10,000 to more than 20,000 donuts per hour, “more for mini-donuts,” Ms. Kimmerly noted. The new system features JBT’s THERMoFIN heat exchanger technology for gentle heat transfer, fast shortening turnover, low frying volume and continuous shortening filtration.

WP Riehle fryers incorporate digital temperature control and hydraulic lifting systems, capable of elevating both the conveyor transport unit and the entire heating system. Ms. Kennedy explained that these lifts are also computer-controlled for easy cleaning, filling and maintenance.

Raising energy efficiency

Many of the design changes in today’s fryers focus on energy efficiency and savings. “Operating cost can make or break the processor’s return on investment,” Mr. Moline observed. Energy efficiency helps raise sustainability ratings, too.

Heat exchangers capture heat from the fryer’s exhaust and help reuse it. “It is not uncommon for such devices to operate at the 80% level of efficiency and above,” Mr. Giles said.

Heat and Control potato chip batch fryers feature a full-length hood enclosing the full frying area, replacing the older style of area hoods partially open to the plant environment. This feature is safer, reduces energy usage and prolongs oil life. “Exhaust volume is significantly reduced,” Mr. Giles said. “This means a smaller, more energy-efficient exhaust fan can be used. The hood also retains heat and steam, which blankets the oil and purges oxygen to reduce oil degradation.”

Fryer manufacturers typically offer both natural gas and electric fuel options. Because utility rates in the US are usually higher for electricity than for gas, most fryer operators have traditionally chosen gas. But that is beginning to change, according to Mr. Moline. Actually, they can have both. The company’s Libra fryer offers gas, electric and hybrid styles.

“Hybrid offers a combination of both fuels,” Mr. Moline explained. “When you need to bring up temperature quickly, as when doing sanitation or starting up, the gas system does the job. And when you get into continuous operation, you switch to the electric system to maintain steady temperatures during long run times.”

Sophisticated energy-saving technology is trickling down from high-volume frying to medium-sized units, Ms. Kimmerly observed, with pre-mixed gas and PLC controls now featured on the company’s 10-ft fryers as well as its largest models. Sensor readings taken at short intervals feed into digital controls programmed to interpret very small fluctuations. “The heating units — whether gas or electric — can apply to smaller amounts of heat rather than being ‘full on,’ ” she said.

The new fryers from WP Riehle take advantage of digital heating controls, using solid state relays. “Digital [control over] heating gives the opportunity to introduce ‘double heating power,’ ” Ms. Kennedy said. “Some open and filled products require significant frying power. If you do not have it, when the products are introduced to the fryer, the temperature of the oil will dive significantly; the ­product absorbs oil and becomes soggy.”

Most of the heat of frying snacks goes into boiling off moisture from the raw pieces. A post-frying drying system can drive off moisture as well. Radio Frequency Co., Inc., Millis, MA, introduced a custom-engineered Macrowave dryer that reduces the moisture of fried snack foods to very low targeted moisture levels. “The new system helps producers of fried foods conveyed through continuous fryers to meet the challenge of obtaining the appropriate color, moisture content and moisture uniformity,” said Timothy Clark, president and CEO, Radio Frequency Co., Inc., Millis, MA.

The dryer uses radio frequency energy, which preferentially heats and dries the moist portions of the load being conveyed through the system. It handles products at bed depths of up to 4 in., thus reducing the length of the fryer while fostering moisture uniformity without over-coloring the product.

Totaling cost of production

Frying equipment must be able to justify its capital cost by delivering finished goods that make a profit. “The current trend is to reduce costs to a minimum while maximizing the return on investment,” Ms. Kennedy said. “In the frying world, this just isn’t the case.”

It’s a fact that new generation oils are more expensive than the partially hydrogenated oils they replace. And as consumers seek more variety in their fried foods and snacks, the costs to procure the required ingredients will increase, too. Premium ingredients will require additional investment in fryer lines, including oil filtration, sediment removal and enhanced temperature control. Fortunately, many of these equipment improvements also aid energy efficiency and sustainability of resources.

Americans love their fried foods — their donuts and snack chips. It’s up to bakers and snack producers to make these foods as attractive as possible.