Ovens: In the zone
October 3, 2016
by Dan Malovany
A high-radiant steel ceiling ensures a consistent, uniform bake by storing and re-radiating heat to crackers.
When it comes to baking, it’s not necessarily about going with the flow but adjusting it to adapt to multiple varieties of baked goods that often require dozens of changeovers on any given day — and sometimes on any given shift. For the most part, gone are the days of dedicated lines where operators fired up the oven and forgot about it. Baking profiles can now be tweaked or tailored not only to a product’s type or size — it doesn’t matter if it’s a cookie, snack, snack cake, bread or par-baked artisan hoagie — but also to its exact specifications.
Even on high-volume continuous ovens, which can churn out thousands of pounds of buns per hour, adjustments can be made to fine-tune consistency in real-time during an extended run or switch over to a new pan size or product variety with barely a hitch. That versatility is needed because change remains constant, even among the nation’s largest quick-service restaurants, now sequentially turning to Old World breads as well as currently on-trend brioche, pretzel rolls and other premium sandwich carriers to boost margins and differentiate themselves from the competition.
“The world is changing, and [bakers] all can look back at their own product mixes from five years ago compared with today’s and see they have added more and different types of products that require an oven with flexible baking performance,” observed Dennis Kauffman, director of baking systems, AMF Bakery Systems. “We offer more independent zone control of heat and recirculated air so the oven can be fine-tuned to a variety of products, all having memory set-points for exact repeatability.”
Air and heat flow often vary in so many ways in ovens today. At the International Baking Industry Exposition (IBIE), set for Oct. 8-11 in Las Vegas, bakers will be able to pick and choose from direct-gas-fired (DGF), indirect-heat, convection, radiant, infrared, cyclothermic and a host of hybrid ovens and a whole lot more.
For instance, Mecatherm’s new FTA oven — a continuous, upgradable single-deck oven — offers six baking combinations, including top convection heating with bottom convection or bottom radiant heat; top radiant heat with bottom convection or bottom radiant heat; or top radiant heating and convection with bottom convection or bottom radiant heat. The company noted such mix-and-match capabilities can bake everything from pizzas, crusty bread on the hearth to panned bread and buns or even bagels, muffins, crème caramel or pies.
Others like Topos Mondial are ratcheting it up a notch at IBIE, promoting the newest J4 oven technology that includes the high-temperature oven outfitted with chain-mounted cast-iron hearth plates for baking Middle Eastern-style pitas and other regional authentic flatbreads, according to Ondrej Nikel, director of engineering. The J4 oven technology uses special burner-radiators to apply intense radiating heat to reach temperatures as high as 500°C (930°F).
“The width, length, number of heating zones and, of course, the temperature profile can be fully tailored to the product’s variety and desired throughput [lb per hour],” Mr. Nikel said. “This is new technology that we didn’t have a few years ago that is now in our repertoire.”
Some of those customizations, he admitted, are a bit unconventional, but an anecdote illustrates the extent of challenges that engineers encounter in today’s global marketplace. One European bakery — desiring to find a way to be independent of natural gas — recently contacted J4’s headquarters in the Czech Republic to develop an oven fueled by wood chip pellets.
“Unlike gas or oil, this unconventional fuel can vary widely in energy content and purity,” Mr. Nikel explained. “But J4 didn’t shy away from the substantial R&D it took to make sure the final bake is right, and the fuel doesn’t have to go on the label among the ingredients. From my perspective as an engineer, we are featuring more customization than we ever did before.”
To accommodate existing and brownfield bakeries where space is a premium, Koenig Bakery Systems USA at IBIE will highlight its new redesigned PU Integral oven, which features a compact layout that leverages modular design and vertical space. The oven’s separate, independent baking zones offer controlled temperature, humidity and air volume as well as an individual steaming cycle prior to baking.
In many ways, noted Rich Breeswine, president and CEO, Koenig, the PU Integral operates like several single ovens. The energy-efficient, thermal-oil convection oven — gas burners are optional — can reach temperatures as high as 280°C (540°F) for baking everything from par-baked to fully baked breads and rolls as well as a plethora of pastries.
Through enhanced independent zone control of heat and recirculated air, continuous ovens can be fine-tuned to a variety of products.
Living with improved circulation
In many ways, ovens are arguably the heart and soul that define the baking process and, ultimately, provide the lifeblood to producing consistent final products. Maybe that’s why circulation — in terms of air and heat — will be the hot topic of discussion throughout IBIE.
BakeRite Systems, for instance, invested in computer technology to improve airflow and application to the baking process. “This new technology has resulted in across and up-and-down-the-band bake consistency,” explained Bill Grutter, vice-president. “Our customers can control the volume of air applied, the areas it is applied to, the amount of direct or indirect heat and amount of recirculating air to be discharged as exhaust. Rather than simply cutting holes in sheet metal for air application, we have engineered nozzles to columnize the air and ensure equal application. We have adjustments to modify the radiant and convective contributions of heat energy and assist in the product’s development, spread, stack height and bake characteristics.”
At IBIE, BakeRite will also display its new Euro-American oven, which, as its name implies, incorporates the latest in European indirect recirculating concepts into a system built in America. “BakeRite has improved and increased the air flow and access to components for service, increased thicknesses of wear parts and provided better control,” Mr. Grutter observed. “We have taken customer comments and complaints on similar units and made changes.”
BakeRite has also enhanced the direct recirculating air oven to increase air flow and outfitted it with motorized dampers that position the air and configure the baking profiles. The system’s control scheme incorporates such variables as temperatures, air flow, baking characteristics and more into its PLC and recipe management system.
Meanwhile, the Gemini W&P Thermador indirect-fired tunnel oven is modular in design and comes in a wide range of custom-tailored widths and lengths. “It is a high energy-efficiency oven featuring high-volume inverter controlled recirculation blowers, a stainless steel steam section with targeted steam delivered directly to the product for minimal waste,” said Ken Johnson, president, Gemini Bakery Equipment Co.
To ensure uniform distribution, the steam quantity and flow direction can be manually adjusted and supplied to both sides of the oven. With W&P’s turbulence design, he added, airflow is reversible and can be from top-to-bottom or bottom-to-top. Each of two blowers in every 20-ft-long turbulence section comes with variable-speed capabilities.
To reduce burner shadowing and increase the allowable space for airflow, Baker Thermal Solutions, a part of the Middleby Bakery Group, designed its 960 Hurricane tunnel oven in 7-ft modular sections. The oven can bake panned or artisan products and comes with a 17-ft-wide flat wire belt that does not require lubrication or tracking and can be flipped for double the lifespan, according to Scott McCally, vice-president of engineering for the group.
The 960 Hurricane uses center-fed chevron burners that — in combination with a variable-speed top and bottom forced convection system — balance lateral heat across the oven without the need for complex zonal burners. Each 7- to 28-ft zone contains its own set of convection and exhaust fans to enhance the oven’s baking performance while saving up to 20% on fuel usage. “The 960 Hurricane boasts true zone control of temperature, humidity and steam, as well as top and bottom radiant and convective heat flux for precise product development,” Mr. McCally noted.
To streamline its tunnel oven’s operation, Babbco air impingement technology features consistent lateral heat balance without the need to continually monitor or adjust a multitude of individual ribbon burners, according William Foran, CEO, Babbco, Inc.
For faster baking times using lower temperatures, Mr. Foran noted, the oven’s variable-speed, recirculating air-impingement fans with automatic damper controls provide independent and powerful top and bottom heat profiles in multiple zones. “High-product yield is another benefit of the Babbco air impingement technology as this style of oven requires much less ongoing and unexpected maintenance,” he said.
Den Boer Baking Systems, meanwhile, has developed a system that can recirculate process air around baked goods to increase the heat transfer to the products while maintaining the advantages of a DGF oven, noted Jim Cummings, president, Tromp Group Americas.
The effect of this flow provides a considerable increase of heat transfer during the baking process, which is reflected by the color and thickness of the crust on the sides of the products. The convection unit comprises a dual-speed or frequency-controlled speed-regulated centrifugal fan, which together with the accompanying air ducts, is installed in the center line on top of the oven. The air extracted from the baking section enters a valve area, which distributes the air over the upper and lower ducts. To control the amount of airflow, servo motors can open and close the valves independently of one another, or a fixed valve position can be chosen.
For flexibility in producing high-quality artisan products, WP Bakery Group will feature at IBIE the Ober Pro, an integrated intelligent control system for loading and unloading processes on deck ovens. The oven loader and unloader can be partnered with the Matador MDV deck oven, which has up to eight decks and can handle more than 800 kg (1,760 lb) an hour. In addition to reducing workload by eliminating heavy physical work, the loader/unloader increases productivity and increases efficiency using WP SmartControl technology that optimizes the fully automated process, according to Patricia Kennedy, president, WP Bakery Group USA.
Ovens with a small footprint can accommodate existing and brownfield bakeries where space is a premium.
Redefining conventional thinking
At IBIE, Reading Bakery Systems (RBS) will exhibit a small section of its PRISM DGF Oven. For many years, Thomas L. Green has used refractory bricks in the crown of DGF ovens to provide a high-radiant surface that stores and evenly redistributes radiant heat back to the products on the baking mesh.
“Radiant heat is a key element in baking crackers — particularly crackers that do not receive post-oven seasoning like oil sprays or slurry application,” explained David Kuipers, Reading vice-president of sales and marketing. “Our research indicated that materials other than bricks can be used to effectively deliver radiant heat to the product.”
RBS recently developed the Thermatec High Radiant Steel Ceiling that ensures a consistent, uniform bake by storing and reradiating heat to crackers, according to Mr. Kuipers. The oven also features large clean-out doors for sanitation and easy access; thick, factory-applied insulation; modular construction; Flynn burners; preheat sections and more. The DGF ovens can be supplied with various burner configurations — either high- or low-density burner patterns — to meet the heat requirements of specific products.
Food safety continues to play a primary role in the evolution of oven design, noted Amaury de Ricqlés, product manager, Haas-Meincke. “Our latest oven design upgrades focus on further improvement in sanitation and efficiency,” he said. “For example, we believe that easy clean comes with easy access, so we can offer our oven modules with height-hinged cleaning doors, staggered on each side, to allow full access inside the oven.” (See “Killer ovens for enhancing food safety” on Page 144.)
Likewise, energy conservation remains top-of-mind, even though natural gas prices — and oil, for that matter — have declined in recent years. That’s because many bakers see energy-efficient ovens as a hedge against unpredictable spikes in energy costs in the future.
In a total cost of ownership analysis, Mr. Ricqlés said, gas and electricity represent around 20% of end product value with about 70% coming from ingredients and other raw materials. Haas-Meincke’s new IFC heat exchanger helps lower energy consumption in a sustainable way.
At IBIE, AMF will introduce a wider continuous system that can produce up to 1,600 buns a minute. To obtain a proper bake at such high speeds, Mr. Kauffman explained that many bakers rely on scientific calculations to determine the amount of energy needed for the process. However, often those preliminary numbers eventually need to be tweaked to accurately reflect the actual baking requirements, and constant monitoring provides greater consistency in the long run.
“Science tells us the BTU per lb to bake bread, but every oven uses more than that in actual operation,” he pointed out. “We are adding more insulation to reduce heat losses. The continuous ovens have a feature to allow baking by humidity, to guarantee optimum moisture within the oven, which is related to bake-out loss — and improving yield and shelf life — and to avoid blotches on buns. There are operator screens that now can display the energy-use rate based on pounds of products in the oven and BTUs being used to bake that product.”
Stewart Systems, a member of the Middleby Bakery Group, will highlight “The Titan” that is capable of cranking out more than 30,000 lb per hr of baked goods. The conveyorized oven features center-fed chevron burners, which light in half the time and with much greater lateral flame consistency producing more than 2,000 BTU per in.
Mr. McCally noted the new dual-zone impingement system delivers a high volume of air from 0 to 4,500 FPM in two zones to control convective heat flux through the pans in one zone and through the products in the second one — both independently controlled by variable-frequency drives. The new system also increases fuel efficiency by as much as 30% by using the waste heat that is otherwise lost through the exhaust system.
An integrated loading and unloading system for deck ovens provides flexibility for producing artisan breads and rolls.
Mind the gap
With bakeries producing so many SKUs, changeovers and shift changes — and, unfortunately, pan jams and breakdowns on the front part of the line — can lead to partially or fully empty ovens in high-volume operations.
That’s why companies such as the Kaak Group incorporate gap control into their systems. “The oven is able to detect precisely when a discontinuity in the product flow upstream is approaching the baking chambers, and through an algorithm, it can track the transit of this gap along the baking chamber,” explained Ashley Morris, Kaak Group sales manager. Simultaneously, the burners’ temperature and the heat distribution dampers are regulated by the amount of product flowing throughout the oven. “This allows precise dosing of the thermal power delivered proportionally to the product distribution into each regulation zone of the oven,” Mr. Morris said.
The so-called “smart control system” can regulate modulation of baking parameters — temperature and humidity — delivering a consistent production and a uniform baking profile even when there are several factors impacting the stability of the product flow, according to Mr. Morris. In the long run, he added, gap management can result in improved yield, minimized waste and reduced energy consumption.
At IBIE, bakers can scout out ovens that also have enhanced safety features. Babbco, for instance, will feature a fully integrated water mist fire suppression system inside the oven chamber to better protect the equipment.
From a food safety and security standpoint, the Kaak Group has incorporated fingerprint administration on its ovens’ HMI to allow access only by approved operators and supervisory personnel.
In the end, the best way to remain in the zone for major capital investments such as ovens involves exploring all of the options and calculating the total cost of ownership for both the short and long run.