Flexible Ovens

by Shane Whitaker
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Ovens not baking products can’t be making any profits. All the same, an item introduced five years ago may not be selling as it once did, so the company may want to make something different in that oven than originally planned. How can a baker or snack processor ensure that its oven is flexible enough to bake not just one product but a variety of different baked foods or snacks?

That is the question any company should ask before making the major investment an oven represents. Because a wider variety of ovens are available nowadays with many more capabilities, engineers must do their homework before making a purchase.

“Manufacturers want equipment that will not sit idle if a new product fails in the marketplace,” said Terry Midden, industry manager, Wolverine Proctor LLC, Horsham, PA. “Asset utilization is one big key to profitability. Products come and go, so the equipment must be flexible enough to manufacture a wide variety of products.” Bakers understand new technologies are available, and many products can be made by more than one oven technology, he added.

While companies generally have one or two products in mind when they purchase an oven, bakers and snack producers usually have enough experience to know that not all new products are going to be successful. “They may want to alter them, or they may have to come up with something completely different,” said Joe Zaleski, president of Reading Bakery Systems, Robesonia, PA. To that end, they should have a fallback plan.

Hybrid styles abound

Reading specializes in ovens for cookies, crackers, pretzels and baked snack products. In fact, baked snacks such as potato crisps represent a rapidly growing segment as consumers’ desire for healthier snacks increases, Mr. Zaleski added.

For these baked snack lines, the company offers an oven with a separate inline dryer after the oven. Separation of baking from drying allows greater flexibility on some product attributes, he said.

If a snack manufacturer tried to reduce the moisture in a potato dough for a baked potato crisp from its initial 40 to 45% to its final 1 to 1.5% in a single baking chamber, the snacks would likely brown. This browning is often associated with higher acrylamide development, which is something the industry is trying to avoid, Mr. Zaleski noted. “By separating the baking and drying processes, it gives you more flexibility on output and controlling some of the coloring attributes of the product,” he added.

Bakers need to look at a couple of things when selecting an oven for the greatest flexibility. First, they need to consider the balance of radiant and convection heat, Mr. Zaleski said. While convection heat can remove moisture, radiant heat develops flavors in products such as crackers. Second, bakers must determine what type of belt they want to use. Often the product range that can be baked is determined by whether the oven’s baking belt is an open-mesh, closed-mesh or solid-steel band. Mr. Zaleski noted closed-mesh belts probably offer the greatest versatility for bakers because they can accept products like cookies that need a more solid belt structure as well as crackers that require airflow through the belt to assist with drying.

Reading’s modular ovens can include hybrid sections that feature radiant/convection zones, where the baker can switch between these two types of heat in the same zone for even greater flexibility. Plenums above and below the product distribute the heated air, and each plenum features a controlled blower, so the operator can vary the airspeed hitting the product, Mr. Zaleski said.

“A series of radiant tubes above the band more or less glow red when firing at maximum capacity, so if you want to bake in more of a still-air oven, you can slow down the convection,” he added. “You use radiant heat to allow the product such as a cracker to rise. Radiant heat doesn’t strip away the moisture layer as fast as an oven with a lot of airflow. The product develops better texture because you are not drawing away the water as quickly as in a drying environment.”

He explained that moisture sitting on the product’s surface fosters chemical reactions within the dough that develop desirable flavors in bread-type items. After dough pieces traverse the development zone in the front of the oven, they enter a section with higher-speed air that will then start drying the product.

Mesh-hearth tunnel ovens from The Henry Group allow a variety of products to bake in a single platform, according to Darren Jackson, COO of the Greensville, TX-based equipment manufacturer. When asked about its most versatile ovens, Mr. Jackson mentioned an oven the company built that included a combination loader/unloader for pan products as well as wing loader to strip products off peel boards to bake directly on the hearth.

Mr. Jackson said the company also supplies ovens that bake both cakes and buns. “Although they both cook in pans, one requires proofing and the other doesn’t,” he noted.

The Henry Group also manufactures a hybrid oven designed for energy savings. Its hybrid oven features an indirect-fired initial section heated by air exhausted from subsequent direct-gas-fired chambers with its ethanol burned off in an oxidizer.

Turbulence allows flexibility

Indirect-fired ovens with multiple baking zones equipped with vertical turbulence zones provide maximum flexibility for specialty bread and rolls, according to Mark Rosenberg, president of Gemini Bakery Equipment, Philadelphia, PA. Turbulence refers to air being withdrawn from the bake chamber and blown back without additional heating through orifices.

By adjusting the vertical turbulence, bakers can quickly tweak top color and help to develop the side walls of their breads and rolls. Turbulence also allows a bakery with a large product mix to adapt from product to product relatively quickly, he said.

In addition, Mr. Rosenberg noted, variety bakeries want to produce hearth and pan products with and without steam. “Our tunnel ovens have independent zone control for moisture evacuation with excellent radiation characteristics, which allows a client to adjust moisture retention during the baking process,” he said. “We can also relatively quickly adjust the heat needed for enhanced color and more stable side walls.”

Gemini recently delivered an oven targeted to produce only hearth products; however, before the oven was even commissioned, the baker determined it also needed to make pan products immediately. “Luckily, the oven purchased had been designed to handle both,” Mr. Rosenberg said.

Harry Jacoby, president, MIWE America, Hillsborough, NJ, claimed the convection heat transfer systems of rack ovens bake the fastest. “It may not be the best for each specific type of products, but it does bake all products well,” he said.

Reducing bake times

Heat and Control, Hayward, CA, and C.H. Babb Co., Raynham, MA, touted impingement ovens for maximum product versatility. Impingement ovens blow heated air at high rates of speed through orifices above and below the products being baked.

Air impingement is very controllable and offers a number of temperature zones,” said Bill Foran, president of C.H. Babb. Independent air distribution ducts above and below the belt gear the oven to product needs. “Let’s say you’re doing a cheesecake where you need a lot of heat into the bottom of the pan but not as much on the top depending on the color you want, then an air impingement oven allows you to transfer that air to the bottom and have very little to none on top. But then if you wanted to do another product like a pizza, where you really want a lot of top and bottom together, you can do that as well.”

Because of the higher air speeds, impingement ovens can significantly reduce dwell times. By controlling air distribution patterns as well as temperature and moisture, bakeries can produce a wide variety of products in air impingement systems, noted James Padilla, Heat and Control’s director of product development.

For even greater flexibility, bakers can adjust the impingement nozzles from 2 to 8 in. above the belt in the company’s standard air impingement ovens, Mr. Padilla said. “That allows you to run a thin product like a toaster strudel as well as something like a chicken pot pie or even a bun by raising the nozzles to the best height for the product to transfer heat at the rate that you want,” he said.

Impingement ovens allow bakers to be prepared should their product portfolios change or expand. “Our customers have their core products, but they also want to plan for the future,” Mr. Foran said. “It is difficult to know what may be the next big thing for your particular company, so flexibility is key. Knowing you can bake a large variety of products in your oven is important.”     

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