A perfect match

by Charlotte Atchley, Baking & Snack
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While mixing may seem straightforward — blending ingredients and developing sponges or doughs — each batch has its own specific needs in the mixing bowl. Meeting those needs is the trick.

“There is more to what seems like a simple process than meets the eye,” said Keith Graham, marketing manager, Baker Perkins, Grand Rapids, MI. “If you don’t get something that will actually mix the dough correctly, you’ve wasted your time and money.”

Some bakers approach their new mixer purchase knowing what kind of equipment they want while others let the final product determine what systems they buy. Each approach impacts the questions they ask their equipment suppliers. According to Jim Warren, director of mixing sales, Reading Bakery Systems, Robesonia, PA, bakers who are equipment-focused will rely on project managers while bakers who are product-focused will rely on R&D teams to guide the discussion. Project managers will ask questions about capacity, temperature and mixing times. R&D teams will focus on whether the mixer will create the desired final product.

“You have to carefully consider all of those things, and you need to have people on your team who have the ability to be experts in the equipment and some people who are experts in the process,” Mr. Warren said.

Oftentimes the product itself will narrow down a baker’s choices between roller bar, sigma, spiral, continuous or other styles of mixers, but beyond that, bakers must consider capacity, efficiency, flexibility, automation and, of course, how the mixer will impact product quality. Working with equipment suppliers, bakers should be able to determine all these factors and more.

“The goal is to place the most efficient mixer in the line every time,” said Sherri Swabb, director of marketing, Peerless Food Equipment, Sidney, OH.

Dough meets mixer

A mixing process must match the product’s specifications. If it doesn’t, bakers can experience a loss of quality and, subsequently, profits. For example, when increasing capacity, large batches aren’t necessarily the answer. “For some products, it’s better to do more frequent, smaller batches equaling the rate per hour that the customer needs to run,” said Kevin Wilkinson, North American sales, Tonelli Group, Redwood City, CA.

Yeast-raised baked foods do best in smaller batches because they are living doughs. With a larger batch, these doughs take longer to process, giving the dough time to change. This causes consistency problems between batches. Smaller batches of yeast-raised doughs help curb these challenges while batters without yeast, such as cookie dough, don’t necessarily have that issue.

Absorption also comes into play with yeast-raised products. Bagels sit at the low end of the absorption spectrum with about a 45% rate, which creates very stiff dough. Terry Bartsch, vice-president of sales, Shaffer, a Bundy Baking Solutions company, Urbana, OH, suggested bakers working with such doughs put horsepower on the top of their priority list when shopping for a new mixer. “The biggest requirement is making sure you have enough horsepower to mix the dough properly,” he said.

On the other end of the spectrum, he said, are English muffins, having absorptions as high as 80%. With such slack doughs, refrigeration becomes critical to maintain machinability.

Proper absorption is essential for a homogenous dough mixture, which in turn is crucial to making consistent dough. Inconsistent dough not only causes final product quality issues but also can make it difficult to process downstream. Pre-hydrating ingredients before the final mixer can improve absorption.

 “The handling of raw materials up front before mixing is the most important part,” said Stephen Marquardt, sales director, Food, Zeppelin Systems USA, Odessa, FL. “With raw material prep, there’s a lot of advantages you can get out of your product quality and savings.”

For example, properly hydrating ensures that minor ingredients will be totally dispersed into the dough batch. Denny Vincent, president of Advanced Food Systems, Columbus, OH, explained that if doughs are not properly hydrated, bakers will need to incorporate higher levels of ingredients like salt, leavening agents and dough conditioners to get the proper effectiveness. When ingredients are properly hydrated, bakers can use smaller amounts of these expensive ingredients.

“We’ve seen some of our customers reduce their ingredient amounts with better hydration,” he said. Advanced Food System mixers ensure this happens with a bowl scraper that incorporates all ingredients into the high-speed mixing tools.

Pre-hydration makes savings possible because it creates a stronger, more homogenous bond between liquid and dry ingredients. Rapidojet, represented in North, Central and South America by Bakery Concepts, Mechanicsburg, PA, improves this bond using a high-intensity mixing process where free-falling dry ingredients are shot with high-pressure atomized water. Higher levels of hydration increases yield, product quality and consistency from batch to batch as well as improve shelf life while maintaining the same level of machinability, according to Ken Schwenger, president of Bakery Concepts.

While non-yeast raised products such as cookies may be more forgiving in these matters, they often carry delicate inclusions that can be damaged during mixing. When Baker Perkins removed the central shaft running through the middle of its cookie and cracker mixer, it cut down the opportunity to damage inclusions. “If you’ve got a shaft getting in the way, it will slow down the process, and you won’t get as even dispersion,” Mr. Graham said. “You will end up with chocolate chips being smeared, nuts being broken or raisins being damaged.”

Exerting control over what’s happening in the mixing bowl also gives bakers the opportunity to ensure product quality. Speed, time, temperature, pressure — all are variables that a baker can control to create the perfect product that’s repeatable. Bruce Campbell, vice-president, AMF Bakery Systems, Richmond, VA, said computer controls allow bakers to monitor dough development while recipe management systems ensure the same results every batch.

Mr. Warren noted bakers can benefit from highly automated production lines that maintain consistent dough day to day. “If you are making a product that has very specific guidelines for the manufacturing, that dough needs to be very consistent to get finished product that you’re looking for,” he explained. “If it’s very sensitive, then you really need to look at equipment that has the necessary controls.”

Falling in line

While a mixer may be one piece of equipment, bakers would do themselves a favor by thinking of it as a part of a broader automated system.

“We start by taking a look at interaction with this mixer from an automated standpoint. How do you load the ingredients from an automated system?” Mr. Bartsch said. “And then we ask to what degree bakers need to be able to access the mixer for hand-add ingredients. When we get to hand-adds, it always seems to be a question they may not have considered.”

When evaluating how to automate a mixing system, bakers must consider any manual steps in their process. For example, must minor or micro ingredients, such as chocolate chips, be manually scaled into the cookie dough?

Many bakers now automate their minor and micro ingredients to improve dough consistency. Reading Bakery Systems’ mixers are self-monitoring, ensuring the consistent feeding of proper amounts of ingredients into the system. If the right amount isn’t met, an alarm sounds. If an operator doesn’t address the problem in a timely fashion, the line shuts down. To accommodate operations that still rely on manual add-ins, some suppliers are enhancing their mixer’s tilting capabilities. For example, a backward-tilting mixer bowl allows operators to add ingredients that are difficult — or too expensive — to automate.

“How do you introduce a block of fat to the mixer?” Mr. Bartsch asked. “The easiest way is with a reverse-tilt so the operator can hand load from the rear, and then they’ll discharge the dough onto equipment in the front.”

Shaffer’s cookie and cracker mixers offer a range of two-way tilting options with 90° reverse-tilting capabilities up to 120 to 140° forward-tilting designs.

Baker Perkins also offers a bowl that tilts backward to accommodate power dough feeders in the front. This 90° reverse tilt enables the baker to incorporate many different kinds of dough feeding arrangements and plant layouts, Mr. Graham said.

Accessibility is also vital when it comes to maintenance and sanitation. “Specifically for a mixer, bakers should ask if they have space to pull out the shaft or change the bowl without impacting other lines,” Ms. Swabb said. While this example may seem extreme, it should be taken into account, she added.

A new mixer can also impact the other equipment in the production line. If bakers are simply upgrading their existing mixing technology for increased capacity, ingredient handling systems and downstream equipment may also need to be updated to handle larger runs of dough or smaller, more frequent batches. However, if a baker is shifting from batch to continuous mixing systems, additional adjustments may be necessary to downstream equipment, Mr. Marquardt said, such as transfers that can handle continuous dough flow instead of dough batches.

No matter what kind of system a baker chooses, dough discharge can be difficult business. After the mixer tilts 90°, operators often have to manually scrape leftover dough off the bowl, agitator and shaft. “It’s a long operation that requires one or two people,” Mr. Graham said. “It’s messy. You’re going to get dough on the floor. It just happens.”

To make this process easier, Baker Perkins gave its mixer a 150° forward tilt, which puts the mixer practically upside down. The mixer is also shaftless, so the dough simply falls out of the mixer unimpeded.

Reading Bakery Systems also incorporated automated discharge into its continuous mixers. Older designs depended on the new dough coming into the process to push existing dough out of the mixer, but now these systems are self-purging, pushing the dough the entire length of the mixer.

Automating the discharge of the batch is another option that allows the baker to do more than just combine ingredients and develop dough. Advanced Food Systems also incorporates dough chunker capability to up the automation ante, therefore automating four steps with one machine.

AMF Bakery’s diverse equipment portfolio helps bakers streamline their process with fermentation rooms, trough hoists, pumps, chunker conveyors and more.

Poised for growth

When automating, bakers should take into account future growth and opportunities. “You don’t want the mixer to be the limiting factor for the line,” said Damian Morabito, president, Topos Mondial, Pottstown, PA. “If the line can do 5,000 lb per hour and your mixer can only produce 4,000 lb per hour, your mixer is undersized for future growth and capacity.”

Ms. Swabb of Peerless echoed this idea that bakers need to always accommodate for the future. “Frequent under-loading or over-loading a bowl can be detrimental longevity,” she said.

Flexibility can exist on several levels including ratcheting up capacity, cranking out a wide variety of products or adapting to other equipment systems.

“If bakers must increase their production rates, or their recipes, their mixer should help to do it through easy tool release and changeover,” said Claire Auffrédou, marketing manager, VMI, Montaigu, France. “All kneading parameters should be variable to adjust to do what the baker wants.”

The mixer design and bowl configuration determines the mixer’s efficiency. The variable-frequency drives (VFDs), agitator configuration and control panels on Topos Mondial’s mixers can be adjusted for various dough absorptions and for the kneading characteristics that are optimal. Their bowl geometry accommodates different sizes of dough. With the appropriate roller bar and stretcher bar positions set, bakers can efficiently mix 300 lb of dough in a 1,400-lb mixer.

“Flexibility is customization, basically,” Mr. Bartsch said. Shaffer offers bakers three tilt options as well as three frame and agitator options that can then be further customized. While bakers can easily anticipate the need for greater capacity, they may find it more difficult to anticipate future new product trends. Mixers come with a considerable amount of longevity, lasting 20 to 30 years. While a production line may now be making buns or flatbreads, 10 years later, the company may diversify.

“The more flexible the layout, the more useful the investment will be as production demands change over the years,” Mr. Campbell said. AMF Bakery offers a range of sizes in four different frame styles that bakers can match plant layout and production requirements.

Adaptability — not just durability — is key to a mixer’s longevity. “On the one hand, the mixer must be able to increase the production rate, but on the other, it must help the baker diversify recipes,” Ms. Auffrédou said.

Having a mixer that can handle those changes can eliminate the need to purchase a new mixer. “If you’re going to keep this equipment [for decades], the more things that equipment can do, the more flexibility it gives the baker,” Mr. Vincent explained.

Advanced Food Systems designed variable speed capabilities into its mixers, letting them handle a wide variety of doughs and batters, including baguette, flatbread, pizza, muffins, cookies or snack doughs, with a 15-minute changeover. If a baker decides to adapt the production line to a new product, all that’s needed is a new set of mixing tools.

For bakers making cookie and cracker doughs, Baker Perkins developed a mixer that handles both. While cookie dough is primarily a blending operation, cracker dough requires the development of gluten. “Usually those products are made on different lines, and you would often have different mixers with different blades, which restricts your versatility,” Mr. Graham said. To address this, Baker Perkins designed a blade profile not only to make soft cookie doughs but also perform the stretching and shearing necessary to develop cracker doughs. This allows bakers to switch to a new product with minimal cost or shift dough output to another production line if a mixer breaks down.

Nimble not only involves flexibility, but it also requires speed — as in how fast changeovers can be made. “All mixer manufacturers are focused on decreasing the amount of time it takes to make a changeover and decreasing the resources required to clean a mixer between changeovers,” Mr. Warren said.

Bakers have long questioned continuous mixers’ ability to deliver speedy changeovers since the technology is ideal for lines with minimal changeovers. To answer that question, Reading Bakery Systems redesigned its continuous mixers to stop the ingredient feed and empty the mixer in preparation for a new product. A PLC holds all the information for every formula, and operators simply choose the formula to change parameters automatically.

Mr. Marquardt said scheduling is important in ensuring fast changeovers. Bakers using continuous systems can switch between varieties with minimal disruption. “For example, if you start with a tortilla that has spinach and then you have a tortilla that has tomato powder in it, we add these ingredients at the end,” he said. This prevents the entire system from being cross-contaminated and simplifies cleaning between quick changeovers with the hygienic design.

Conserving energy

While today bakers may look at buying a new mixer because of growing needs for more capacity, Mr. Morabito predicted that soon bakers’ will look for new equipment for the energy savings. Topos Mondial’s mixers can cut amps and cooling needs in half and mix times by 30%. “You’re making money by upgrading your mixer because you’re saving all this energy cost,” he said. “Going forward, energy efficiency is going to justify new mixer upgrades.”

Topos Mondial achieves those energy savings with its VFDs, bowl geometry and proper roller/stretcher bar positioning. This creates an efficient mix at a lower rpm, saving horsepower, amp draws and bowl cooling energy.

Variable-speed drives (VSDs) are critical in making mixers more energy efficient. As Mr. Graham explained, mixing processes require two speeds: low for blending and high for dough development. Two-speed mixers create a sudden spike in energy, which creates expensive energy bills. VSDs start the mixer gradually without power spikes. “It’s kinder on the mixer, it’s kinder on the electricity bill, and it’s probably kinder on the product as well,” he said.

Continuous mixers also help with those energy spikes, according to Mr. Marquardt. Because the mixer creates a continuous flow, bakers can see up to 30% less energy costs, raw material savings, no ice or CO2 for cold doughs and a line efficiency increase up to 5%.

Rapidojet’s instantaneous dough development happens with limited energy input. While a traditional mixer uses approximately 15 kw-hours per tonne of dough, Rapidojet consumes about 1.5 tor 1.6 kw-hours for the same quantity, making it formidable in beating energy costs.

These levels of savings will encourage mixer upgrades as bakers continue to search for ways to save on cost. 

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