Baking conditions are inherently dynamic–a situation that makes baking consistent products from the beginning of a production cycle to the end a challenge. And as critical as the baking process is, it’s important to recognize that the process begins with dough mixing, says John Squire, district manager, Kaak Group North America, Lithia Springs, Ga.

“An inconsistent dough means the baker will never be able to have real process control in the bakery. Attention to the fl our quality from the mill during seasonal changes and the required adjustments during mixing will enable the baker to begin to control his process,” Squire says. “[Other] factors, such as proper water temperatures, monitoring fl our temperatures and mix times [also] are important. Seasonal adjustments in the bake process are often needed due to changes in seasons as the humidity in the air is different winter to summer.”

 rough trial and error, bakers determine proper set points and controls for the baking process. But operators often must react to changing conditions, such as production stoppages and variances in load demands. Bakers also are faced with multiple changeovers. Unless the oven is emptied out completely between changeovers, product might end up overbaked or underbaked. That’s where production management plays a role. “ ere is such a thing as feathering, where you slowly increase the [conveyor] speed or decrease it, and you can change the temperature slowly,” says Geri Walker, president, Bake-Tech, Tucker, Ga. “Ideally, you have to empty the oven out.”

Bakers currently may bake their products in older-style ovens where there is limited opportunity to adjust to changing process conditions. But those in the market for a new oven may consider the multitude of technologies available for producing high-quality, consistent products based on the bakers’ product mix, desired throughput, available footprint, growth plans, available energy source and numerous other criteria.

Solving the lateral heat problem

“In the past, it was difficult to get consistent baking because as product moved through each of four zones in a typical 100-ft. oven, the lateral temperature, or temperature across the oven, would vary,” says Jim Diver, V.P. operations, Dunbar Systems Inc., Lemont, Ill.

“In other words, how do I get the same heat on this side where my gas is coming in, versus the far end where maybe I lost all my gas and used it across the burner,” Diver says. “[In newer oven models], you have an orifice that’s adjustable, which uses minimal gas [at one end], and opens up so you get more gas down at the opposite end.  e issue that comes up with lateral heat is that you can look at [one] side and see it is dark brown, while [the other] side is light.  at would be a direct-fired oven. You try to get balance. Various burner manufacturers have come up with different devices to adjust their lateral heat by adjusting the amount of gas flow that’s going through that tube.”

Heat source

Commercial bakery ovens vary in construction design, footprint and method of heating, among other parameters. Energy sources used to heat ovens include electric, gas, thermal oil and infrared. Ovens also are heated by convection, or circulating hot air.

“Electricity is the most expensive fuel for baking. It’s convenient and easy for a small operation to use without the expense of a thermal oil system to pipe in,” Diver says.

Yet more bakers are turning to thermal oil as an energy source as concerns about carbon emissions increase. Thermal oil requires the least amount of energy for recovery. For instance, at Tasty Baking Co., Philadelphia, five newly installed Auto-Bake ovens use thermal oil that only require 5° F reheating on the return, Diver notes. Thermal oil gives consistent bake for all products. You don’t have to worry about light or dark product or lateral heat, he adds.

But Walker feels gas burners are the way to go. Gas responds immediately, whether it’s the beginning of a production run, the end or a line stoppage. “You have to be able to shut that heat off,” Walker says.

Flash heat, or a sudden burst of energy, can occur in ovens, particularly during short runs or large gaps in production. “Kaak’s MCS oven has a unique feature where it registers a gap in production so as not to create an improper bake. Often, bakers will load empty straps in the oven before and after a short run to absorb the heat and not flash the product,” Squire says.

In the old days, bakers would run pans with bricks or water in them to soak up the flash heat, Walker adds.

Continuously consistent

A wide variety of ovens exist for bakers, including tunnel ovens, rack ovens and deck ovens. But it’s the continuous oven that’s synonymous with consistent baking, Walker says. When a tunnel oven is loaded with seven pans on a 12-ft. tray, heat has to be applied evenly across all pans. In a continuous system, the width is not 12 feet, but three feet. “We group pans in groups of one as opposed to seven,” Walker says.

The continuous oven uses an endless type of conveyor system. Burners sit under the conveyor in the straight lengths. Air can be in the curves, straights, or recirculated via ceiling fans. The air blows consistently and helps even out the heat to the pan, he adds.

“Burners are parallel to the conveyor, and are typically 10 feet to 20 feet long. The burners run parallel under the pan and light the pan from right to left as it is conveyed down the oven. The front end of the burner may be on the right side of the pan and the tail end of the burner is on the other side of the pan. Sometimes there are burners on both sides of the pan,” Walker adds.

“Another point about a continuous system is you don’t have a lot of mass to heat. You have the conveyor system, while in a tray or tunnel oven, you have trays that are massive. The trays hold a lot of heat, so they take a while to heat up and take a while to cool off. They’re slow to change,” Walker says. “Basically, the product goes in and the burners respond to the load. The consistency you get out of a continuous system is superior to what is physically possible in a tray or a tunnel oven, just because of the mass.”

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