Not long ago, bakers had to wait for a half hour or longer to adjust their ovens before running another product requiring different temperatures, times and myriad other baking parameters.
Now changing overs can be done in minutes, which enhances a production line’s yield while reducing waste and improving overall product quality.
Overall, adjusting oven temperature depends on various factors. In an Auto-Bake convection oven, for instance, the transition time between temperatures of +/- 30˚F and less can be achieved in fewer than 5 minutes, noted Scott McCally, president, Auto-Bake Serpentine, a Middleby Bakery company.
He pointed out that the size of the zonal package burners along with large exhaust fans, which bring in a high volume of cool ambient air when necessary, reduces oven temperature quickly.
Brent Grantham, national account manager, Middleby Bakery, suggested that some baking profiles can change almost instantaneously by focusing more on Btu input than temperature to optimize oven performance in Baker Thermal Solutions ovens.
“In fact, theoretically we can have multiple products in a single oven at the same time,” he said.
Jerry Barnes, vice president, Babbco, pointed out that the company’s air impingement ovens come with stainless steel interiors that provide hygienic design and avoid flash heat.
“Flash heat is the bane of a direct-gas-fired (DGF) oven, no matter how good the cutback or gap control,” he said. “Our air impingement ovens automatically change damper settings and zone temperatures within minutes, providing extremely quick changeover capability. Products entering or leaving the oven do not suffer from dark or light coloring. Because changeover is so quick and waste is not produced, the utilization is very high, leading to greater throughput.”
Kevin Knott, technical sales manager, Haas, a Bühler Group company, noted that 5- to 10-minute changeovers can be made when using convective heat. However, that’s not always the case with other types of thermal heat, which can take 45 to 60 minutes to take full effect.
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“Most of today’s ovens have automated controls on dampers and temperatures, controlled by a PLC with a recipe management system that enables the operator to make the changes in an efficient manner,” Mr. Knott said.
Marie Laisne, Mecatherm’s oven product manager, said fast changeovers depend on an oven’s responsiveness. Mecatherm’s M-TA oven offers direct heat, a powerful fan and a modulating burner to swiftly refresh the air flow to the required temperature inside the oven while avoiding flash heat. Along with recipe controls, Mecatherm can optimize the steam damper’s settings.
“This feature allows bakers to quickly set the optimum baking settings to achieve the desired product quality with minimum energy consumption,” she said.
Ken Zvoncheck, director of process technology, Reading Bakery Systems (RBS), said changeover times and temperatures vary on the type of heat.
On baked snack lines, changeovers typically take about 20 minutes to prepare dough’s and adjust other front-of-the-line settings. During that period, a DGF oven will begin to overheat, prompting bakers to shut off burners and increase belt speed to prevent new products from burning during the start of the next run. A convection oven, he added, can sit idle and not overheat because the burner is in a separate chamber, relying on hot-air velocity to heat the oven.
While RBS offers DGF and convection ovens, Mr. Zvoncheck observed that the latter is simpler to operate. A convection oven has only one burner per zone compared to a DGF oven, which may have up to 40 burners per zone.
“As you might imagine, the amount of maintenance spent on those few convection burners is much less,” he said. “It also gives the operators more standardization of baking. If you have 250 burners in the oven, they have many more burners to turn off and on to choose. Rather than turning on multiple burners on the top and bottom in each zone, all we’re doing is simply punching in a number from zero to 100% to set what convection velocity we want above the belt and below the belt.”
In theory, the baking process seems as simple as 1-2-3, but it takes a combination of the latest in technology and process controls to make sure that a wide variety of products are baked to perfection every time.
This article is an excerpt from the November 2020 issue of Baking & Snack. To read the entire feature on ovens, click here.