Bars are interesting products. In the past decade, the category has exploded to include varieties ranging from cereal and snack to energy and nutrition, and they’re made with every thick, chunky, sticky or crunchy concoction a formulator can dream up.

In April, Mintel predicted that the sky’s the limit for bars, based on data in its “Snack, Nutrition and Performance Bars” report. According to the research firm, it’s that wide range of product types driving the growth. The report indicated that 53% of consumers are eating bars as a treat, and decadent fillings and inclusions are catering to that desire.

Not to discount the protein craze, that is. Mintel noted that nuts — specifically peanuts and almonds — are big growth drivers for bars, and innovation with ingredients like cashews is also gaining ground.

“The bar category has experienced a lot of innovation in the past couple of years,” said Sebastian Clemens, sales account manager, Bühler. “Ingredients and format have changed drastically, and this requires flexibility and advancements from the manufacturing equipment.”

Moving this type of dough (if one can even call it dough in the traditional sense) through the process without damaging it — or the transfer equipment — takes a bit of mastery and attention to detail.

Staying together

Today’s bar doughs often come with big, heavy inclusions that must maintain their integrity throughout transport. Think of products like KIND Bars with clear wrappers showcasing whole nuts, fruit pieces and other wholesome ingredients.

“Maintaining product characteristics that were developed during the mixing stage through the transferring and extruding process is a major concern for the bakers. Naturally the dough will slightly change over time, and the forming or extruding equipment will start working it. Selecting equipment that minimizes these changes is critical,” said Cesar Zelaya, bakery sales and technology manager, Handtmann, Inc.

This also can present some challenges in equipment like chunkers, pumps or extruders. “When processing dough with hard and dried inclusions such as nuts and seeds, bakers need to look for heavy-duty versions of pumps and chunkers,” Mr. Zelaya said. He noted the company’s Vane Cell pump is designed to minimize breakage of inclusions like these.

Viscous ingredients such as molasses, honey and corn syrup make for dry, stiff dough. The lack of water content makes the dough more difficult to handle, which can affect the process and necessary equipment.

Bar inclusions can also be fragile, so it’s important to have a transfer system that can handle a variety of textures. “Mixed materials can be soft, fragile, flakey or dense, so you need to look after all aspects and components of the mixture,” said Norman Schmidt, president, Food Machinery Engineering (FME), which partners with Reiser for dough handling equipment.

One option for consistency in dough is the use of continuous mixing, especially for high-protein doughs that have a tendency to change with time. “Proteins in dough undergo change as it rests, which makes it more difficult to form,” said Sam Pallotini, director, cookie, cracker and pet food sales, Reading Bakery Systems. “This change can occur randomly for different products depending on temperature, hydration and protein levels.” He suggested that a continuous mixing system can limit the need for additional auxiliary equipment to transport dough and feed the forming equipment.

Moving right along

All the inclusions — and the honey, gums and syrups that hold them together — have bar dough slogging slowly down the line, and that creates all new obstacles compared with handling more traditional bread and roll dough.

Oftentimes, the challenge starts the minute the dough leaves the mixer. “Good handling of sticky dough starts here,” said Damian Morabito, president and CEO, Topos Mondial Corp. The company recently built a mixer with a 160-degree overtilt so that the bowl can face all the way to the floor. “The product can discharge straight down onto a belt, trough or some sort of feeder, and it won’t get hung up in the mixer,” he said.

But the mixer isn’t the only thing the dough is going to stick to. Consider all the surfaces that are moving the product down the line. “The next challenge is that when it goes into a hopper or a chunker, it wants to stick to the walls, the chunking blades, even the belts,” Mr. Morabito explained.

One way to keep from leaving so much product on the equipment is with the finishing on the food contact surfaces. For instance, Topos will often use a swirl finish on stainless steel hoppers to aid in release. “The swirls you see on machinery may look decorative, but it actually aids in the dough release because it minimizes the tension between the dough and the metal surface,” Mr. Morabito said. “If you think of it microscopically, it’s raising the metal edges up, and there’s less surface for the dough or mixture to stick to.”

That sticky consistency might seem impossible to release, but advances in coatings are making a big difference. “We’ve had success with doughs that were so sticky we never thought it would chunk,” Mr. Morabito recalled. “We’ve done FAT tests with certain sticky material and found that a traditional triad blade chunker, with three blades on the shaft, has been able to chunk it and feed it onto a belt, up the belt elevator and into the hopper.” Part of the easier release is due to the coating on the blades; part of it, though, also comes from their programmable rotation back and forth.

Moving bar dough out of the equipment is one thing, but bakers must also address the challenges that come with getting it the next point in the process. “The feeding of mixed materials has to be at a more consistent rate than with other bakery products,” Mr. Schmidt said. “Too much, and you can overload the bar formers; too little, and it starves out.”

Mr. Schmidt also pointed out that storing a reserve of dough in a hopper, as done with traditional dough, doesn’t equate in bar production. “You have to look after a wide range of bar mixes, so dedicated transfer equipment built for single purpose products is not acceptable,” he said. “Whatever we have to contend with for bread and roll bakeries, the needs for bar producers has been an order of magnitude — 10 times — higher and more demanding.”

Geometry can help, according to Mr. Morabito. For example, hoppers used for traditional doughs typically have an inverted pyramid shape, which doesn’t bode well for for a mixture for bar products. “For sticky products, you need to build hoppers like chimneys, straight up and down. Let gravity be your friend and allow the dough to go directly onto a belt or chunking blade,” he said. This will avoid getting the dough stuck on the sides and wedged into the narrowest part of the hopper.

Powering up

One way to ensure that dough stays on the move, Mr. Schmidt noted, is by designing specialized equipment that has enough power to handle the dough. “When you build a lot of specialized machines, you know what to expect, and by doing a few tests, you can gauge what is required from your drive system,” he said.

Oversizing the drives — the service factor or safety factor — provides the necessary torque. “We typically oversize motors and drive systems to increase the service factor, which helps avoid issues and failures,” Mr. Schmidt said. He suggested paying close attention to shaft and bearing loading. “Shafts with longer overhung loads will usually have higher stress levels than motor and gear output shafts,” he said.

Remember the adage, “Less is more” … now, throw it out the window. Think more: more horsepower, more gearbox size, more safety factor. “These firmer, drier ‘doughs’ will add a lot of power requirements, so you need to engineer the gearboxes to a higher, heavier-duty spec,” Mr. Morabito said. On a belt, the stickiness will act like a brake, and the dough won’t convey, so oversizing a gearbox with a safety factor of 2 or more (Topos recommends 1.25 or 1.5 on traditional dough applications) will give it the power it needs.

Mr. Morabito advised that the safety factor doesn’t apply when the operation is in a steady state. “It’s when things go awry — someone added too much molasses or not enough gum so it became extra sticky and firm — that’s when the product becomes abnormal and still runs through the machinery; that’s when you can break it,” he said. Designing the gearbox, belt rollers and bearings with a safety factor will ensure that the transfer equipment will be able to handle it. “Or at least set off an alarm so it doesn’t create damage downstream,” he added.

High sugar content makes dough sticky, and that problem increases exponentially for bar doughs. To address this, Handtmann designed its transfer equipment with an adjustable vacuum pump. “This allows us to vary the required power to process different types of dough formulations from soft and fluffy to hard and dense,” Mr. Zelaya said. “For cases where high torque is required to pump and process dough, Handtmann offers a high-pressure extruder that can operate at a high-pressure level to pump hard and sticky dough that will not work under standard extruding conditions,” Mr. Zelaya said.

On the other hand, Mr. Clemens suggested that a “go big” mentality isn’t necessarily the only choice. “It is important to determine and resolve the root cause rather than just using larger motors,” he said. “Depending on the application, we will use belt materials that minimize the sticking as well as cooling tunnels and a design that ensures the residual binder is scrapped and washed off properly for smooth transfers.”