Custom Curves
For a tailor-made bake profile, bakers can explore the possibility of hybrid ovens. Hybrid ovens — some of which are modular, some are not — incorporate multiple heating methods into one oven. These combinations allow bakers to optimize their ovens’ profiles.“Hybrid ovens are designed around the baking profile of a specific range of products,” Mr. Kauffman said.
The company supplies hybrid ovens that match two or more methods of baking — direct-fired, indirect-fired, convection or impingement and steam— to get the desired profile and finished product. Understanding the role of each heating method can help bakers recognize how they work together to make the most efficient bake.
“Each product is a little different, but the physics of baking comes down to three modes of heat transfer: radiation, direct contact or conduction, and contact with the flow of hot air or convection,” Dr. Nikel said. “These three modes are present in every oven, but the oven modules can be optimized to emphasize one over the other three.”
Cyclothermic modules likes those in J4 ovens, sold in the United States by Topos Mondial, balance all three heat transfer modes. Radiation is produced with STIR and controlled by setting the temperature. Convection may be set in real time with the speed of the fan, and conduction is controlled by the choice of hearth material and via the baking pans.
Direct gas-fired, which uses radiant heat transfer, can set the product’s initial shape and size. Conduction heating is surface-only heating and works well with thin products such as pizza crusts and flatbreads. Air impingement or convective heating relies on air turbulence to remove moisture from the product.
Bakers can combine these heat-transfer methods and others into one oven in the appropriate sequence to get the exact baking profile to best suit their products.
“Another benefit would be the ability to use different heating methods above and below the product either for surface finish of a hearth-baked product or for maximizing efficiency of getting energy into a pan-baked product,” Mr. Stockton said. “The ability to change from conventional direct-fired to infrared to variably controlled impingement heating technology in the same space may be beneficial to customers who need to produce multiple products in the same production space.”
In a pizza crust application, this could include air impingement above the hearth and direct-fired burners below.
“This would allow for better control of the bake throughout the oven,” Mr. Stockton explained.
Babbco’s hybrid ovens can combine any of seven different technologies: air impingement, direct-fired, thermal oil, radiant, indirect-fired, electric or infrared.
“Although any types of oven could be combined in any order to form a hybrid, by far the most common is direct gas-fired at the start followed by sections of convection heat in the middle and at the end,” said Keith Graham, marketing manager, Baker Perkins.
Having direct gas-fired at the front of a hybrid oven allows bakers to transfer heat to the product using only radiant heat.
“So direct gas-fired is great for starting to set the product and the initial shape and size and even a little color, but we don’t want the turbulent air of convection style of impingement to dry the skin of the product so that moisture can’t escape,” said Scott Fischer, vice-president, sales and marketing, Advantech.
The combination of direct gas-fired and impingement delivers this bake profile commonly used in hybrid ovens and beneficial to products like cookies and crackers. Hybrid ovens for these products are often composed of convection, direct gas-fired and radiant zones, said David Kuipers, senior vice-president of sales and marketing, Reading Bakery Systems (RBS).
“There are often three primary sections to the baking process: development, setting and coloring/drying,” Mr. Kuipers said. “Hybrid ovens where the last zones are convection will allow these final sections to be more efficient at drying. This helps with uniformity of moisture in the final product and product quality.”
Balancing the removal of moisture without over-coloring a cookie or cracker can be tricky. Adding a dryer after the oven can assist in striking that balance. Radio Frequency’s Macrowave RF Post-Baking Dryer preferentially targets excess water remaining in the interior product while also equilibrating the moisture throughout the product to achieve the desired quality.
“Without the over-cooking and over-coloring that additional convection cooking causes, the Macrowave efficiently and cost-effectively accomplishes the desired result, improves shelf life and eliminates checking,” said Lisa Mitchell, marketing manager, Radio Frequency.
