When it comes to the science of baking, establishing the proper initial heat profile remains particularly vital to consistency and quality because that’s where the development of the product takes place.
“Setting the proper temperature, exhaust and type of heat application in this zone can be the difference between achieving a decent final product texture versus something that is superior in terms of development,” said Ken Zvoncheck, director of process technology, Reading Bakery Systems. “Thin products tend to be baked more quickly at higher temperatures whereas thicker products generally need more time in the oven in order to achieve a thorough bake throughout the center of the product.”
With breads and rolls, applying a mist of water between the proofer and oven moistens and cools the dough pieces. This allows the steam to condense more readily.
“It actually amplifies the steam in the oven,” said Ondrej Nikel, director of engineering, Topos Mondial. “It’s the holy grail of simplicity for adding steam to your products.”
Normally placed just inside the oven entrance, steam lances rely on low-pressure conditioned steam.
“The key is to not overheat this entrance section to where the steam effect is diminished,” cautioned Jerry Barnes, vice president, Babbco. “An extraction fan is most often employed directly after a steam lance zone to prevent steam migration throughout the bake chamber. Failure to use this effectively can create corrosion in later oven sections not having a stainless interior.”
Phil Domenicucci, baking systems specialist, AMF Bakery Systems, pointed out that steam tunnels are used only at the oven infeed when the products are cool enough for the steam to condense on their surface.
Remco Bijkerk, executive product manager, AMF Den Boer, AMF Bakery Systems, added that controlling such condensation prevents the products from drying out too fast on the outside. By adjusting the humidity level, the dehydration rate can be controlled. He added that condensation will only take place when the products’ surface temperature is below the dewpoint temperature of the process air.
“Once the product surface reaches a certain temperature the so-called dewpoint temperature, additional steam is useless because it will not condense and may cause blotches from water droplets on the product’s skin,” Mr. Bijkerk said.
At the end of the steam tunnel, Mr. Domenicucci said a separate exhaust removes the excess moist air, which develops the crust and a shiny texture.
Sveba Dahlen, a Middleby Bakery company, uses a steam generator that creates a mist by flushing water on heated steel balls and/or aluminum rods. Mikael Ljunggren, master baker, Sveba Dahlen, noted the product can spend anywhere between 5 and 30 seconds under steam depending on the desired characteristics.
“If you see that your products require more steam, you can easily add extra by pressing and holding the steam button on the panel for as many seconds as you want, and the extra steam will be injected instantly,” Mr. Ljunggren said.
Billy Rinks, national sales account manager, North America, Stewart Systems, a Middleby Bakery company, noted its ovens rely on up to five steam banks in the first zone for proper crust texture and appearance. Automatic controls and exhaust vents control the amount of relative humidity throughout the ovens’ other zones.
“The way we achieve this is by adding steam into the first zone of an oven rather than if it’s a conveyorized or tunnel oven,” Mr. Rinks said. “We only use saturated steam for this process. We have several banks of nozzles in the steam tunnel, which is used to isolate the steam in that zone. Typically, the burners are off in this zone when using steam.”
On Gemini Bakery Equipment’s indirect-fired tunnel oven, targeted steam is delivered directly to the product for minimal waste.
“Steam quantity and moisture levels are manually adjustable or can be automated and custom-profiled for each product,” said Ken Johnson, president, Gemini Bakery Equipment. “A stainless-steel moisture evacuation duct with a manually adjustable damper is in each 20-foot-long oven temperature zone. These dampers can be automated with linear actuators for best repeatability. The ideal rate of steam retention or removal can be profiled for each product.”
To obtain the proper baking parameters, Davide Deppieri, master baker, Tecnopool, observed that studies have documented the proper interaction between the dewpoint and the oven, crust and dry bulb temperatures.
“We normally suggest our customers use low-pressure steam, and we have created a customized pipe system for the injection,” he said. “However, the system to remove the steam excess is more complex to manage, particularly in a tunnel oven. The extraction dampers play an important role since the oven spring and the addition of steam involves more than 15% of the total length of the oven.”
Mr. Nikel noted that Topos Mondial designs its J4 ovens to tailor the amount of steam throughout baking process. In the initial zone, it can offer up to twice the number of steam injection pipes if the product requires them. Automatic controls wait until the oven zones rise to the proper temperature, then adjust the amount of slightly pressurized steam so that it readily condenses on the product.
“There is a challenge with injecting steam, so it is not too hot and not too pressurized,” he said. “It will want to condense, and you may get droplets coming from the steam supply, so they could ruin your product. For that reason, our steam injection pipes are equipped with an outer jacket, a design that ensures the liquid condensate droplets are removed from the injected gaseous steam.”
If necessary, bakers can lower a mechanical curtain made of a heat-resistant, woven mesh to effectively cause the steam to flow throughout the entire baking chamber to obtain a chewy, thicker crust. Another option, Mr. Nikel noted, involves a hot-air curtain that controls the distribution of moisture. A fan outside the oven blows ambient air that gets heated up when it passes through a tube embedded in the hot burner chamber.
“The hot air expelled via array of nozzles then effectively forms a curtain, which works much like the curtain that we all know and experience at the entrance into a mall or a hotel during winter season,” he explained.
This “wall of hot air” acts to stop the steam from propagating. Typically, he added, the J4 oven will have at least three or four valves or other control features to ensure the oven contains enough steam and provide additional control to achieve the desired bake on each product with quick changeovers.
This article is an excerpt from the June 2020 issue of Baking & Snack. To read the entire feature on ovens, click here.