Depositing difficult doughs
November 28, 2016
by Laurie Gorton
Screw augers, instead of rollers, deliver dough in this depositor.
Gluten-free baked goods continue to catch consumers’ eyes, thus presenting producers with the challenge of ratcheting up output. Rising demand means that the manual methods they relied upon to launch their products can’t keep up. But when automating such breads and rolls, it’s the dividing and depositing stages that present special difficulties.
Gluten-free and other non-standard doughs are often fragile. They depend on starch and gums for structure and can be easily damaged if put through conventional equipment. Their sticky, gassy nature makes them adhere to food-contact surfaces, and their leavening system can run ahead of divider speeds.
“With gluten-free doughs, you’re always pursuing a moving target,” said Stewart Macpherson, vice-president, sales and marketing, Unifiller.
It’s not just gluten-free doughs that act this way, so do ciabatta, focaccia and other high-absorption styles. The question is: How does a baker go from hand or semi-automatic methods to achieve the larger scale and full automation needed?
From a process standpoint, the nature of these doughs often sets them up for failure. “There are two chief challenges to gluten-free,” Mr. Macpherson said. “First, the structure of the dough is quite fragile and delicate. Second, there can be, depending on the formula, constant changes in specific gravity. The consistency of gluten-free doughs can change very quickly through rapid aeration.”
High-absorption doughs don’t run like other doughs. “They do not portion or cut like standard bread or bun dough,” observed John McIsaac, vice-president, strategic business development, Reiser. “Therefore, different portioning and dividing steps are required.”
The problems show up early in the process at mixer discharge and later during conveying and forming. “Comments on specialty doughs have remained consistent through the years, starting with the low-fat craze,” said William Grutter, vice-president, BakeRite Systems. “Oftentimes, more horsepower and larger shafts are required.” Some solutions involve reductions in batch sizes. But, he warned, “profits are made on larger batches and lower labor production costs, so process reductions are seldom acceptable.”
Such doughs are just plain more difficult to process, according to Keith Graham, marketing manager, Baker Perkins Ltd. “The challenge with any dough dividing is to achieve accurate scaling with minimal damage to the dough structure,” he said. “Dividers are volumetric devices, so the gassier the dough the harder it is to achieve the consistent density that is required.” He noted, as well, that sticky doughs can cause unacceptable build-up.
As a result, the equipment choice for dividing or depositing these types of doughs differs from the technology used for conventional bread and buns. At Rheon USA, for example, the company’s KN550 Co-Extruder offers an advantage. “Coextrusion can damage the gluten structure of regular doughs, but doughs without gluten run well because the machines are designed for high-hydration doughs as well as materials as sticky as caramel,” said John Giacoio, national sales manager, Rheon USA.
“It’s the act of forming that is the most difficult for these doughs,” he added. “With a coextruder, the dough comes out in stick or ball shapes, easy to make into hot dog or hamburger buns, even bagels. Our V4 Stress Free divider was designed to handle doughs with absorptions as high as 80 to 90%, and that’s in the same ballpark as gluten-free.”
While gluten robustly binds water, the rough handling of gluten-free doughs can release water undesirably. Starch granules in gluten-free flours, such as rice, tend to be more fragile than those of wheat and rupture more readily. These concerns can be answered by low-stress systems.
“Sticky doughs and doughs with high hydration points require different processing than drier or stiffer doughs,” explained Eric Riggle, vice-president, Rademaker USA. “The first thing Rademaker does is develop a solution that does not make the stickiness worse, and this usually involves some sort of a low-stress dough sheeter.”
Mr. Riggle recommended the company’s LSS low-stress sheeter and the DSS double chunk sheeting system. “These solutions do not create additional tension or damage to the dough during the sheeting process and, therefore, do not cause the dough to release any additional water due to stress,” he said. “The more gentle the process, the less dusting flour is required and the less build-up of dough on the equipment.”
Servo controls help lines run smoothly and quietly, according to Jim Cummings, president, Tromp Group. “Our Unimac Series works best for these products. We make a range from 24 to 48 in. wide. Customers are happy with the weight control and the simplicity of the machine.”
A double-screw pump delivers sticky doughs in accurate portions.
A matter of release
To dial in on the stickiness problem, manufacturers offer a number of approaches. Mr. Grutter cited better release materials and coatings, such as UHMW and Delran, for the hoppers of the company’s depositing and wirecut systems to reduce the coefficient of friction between the machine and the dough. “On occasion, we will also coat stainless-steel surfaces with food-grade materials that have high release characteristics,” he said. “These can be expensive and may require recoating in a couple years, but they greatly enhance the feeding and machining of dough pieces.”
There are mechanical answers, too. Mr. Grutter pointed to scrapers for conveyor belts that remove old materials that may have adhered to the belt.
“When possible, we modify the dough contact points rather than create new special machines for sticky or difficult-to-handle doughs,” Mr. Grutter noted. “We will also research the processing characteristics of the dough to see if drive train modifications are required.”
UHMD plastics used for the cutoff device play a vital role in Rheon’s coextrusion systems. “The only thing the dough touches is the shutter,” Mr. Giacoio said. “And nothing sticks to that,” he said.
The action of cutoff mechanism was also noted as another critical aspect described by Mr. Cummings. “With Tromp Group equipment, we provide shutoffs, but we find a traveling up-and-down motion or the use of rotating nozzles to be much cleaner ways of breaking the dough or batter between portions,” he noted.
Just getting the dough to the depositor or divider can pose problems, too. “In the matter of dough constantly changing over time, we can pump softer doughs using the Hopper Topper Max system,” Mr. Macpherson said. “It moves them from the mixer directly to the depositor’s hopper. The system keeps the level of the dough and its weight constant in the hopper.”
Mr. Giacoio observed, “The biggest hurdle is after the divider, getting such doughs through the moulder. It also goes back to the customer’s formulation. The biggest challenge is shaping of the final product.”
A driver roll inside this divider ensures transfer of 80%-absorption doughs from the pistons to the rounding drum.
Tooled for the job
Accuracy marks a common theme for bakery machinery that must run high-absorption doughs at the high speeds of automation.
Because flow problems characterize many specialty doughs, bakers can look to extrusion methods that use positive feed mechanisms such as augers. “Handtmann dividers feature a variable-frequency drive-controlled feeding auger in the hopper to consistently feed dough into the divider and guarantee the weight accuracy of dough pieces,” said Cesar Zelaya, bakery sales and technology manager, Handtmann, Inc. “For doughs with particulates, the company offers a bigger pump set with less stress and a shorter path for the dough going through the divider or depositor to minimize the damage to inclusions.”
Mr. Zelaya noted that the Handtmann VF-620B operates on a 1% standard deviation. “However, for cases where gentle dough handling is more critical than dough-weight accuracy, we can reduce the vacuum level in the machine and minimize the mechanical action on the dough through different dough pump configurations and still achieve a 2% weight variation between pieces,” he said.
Configuring Reiser’s Vemag with various double-screw pump assemblies can tailor the system to the wide range of viscosities common to gluten-free and specialty doughs. “We select the proper setup of the divider for the dough to ensure gentle accurate portioning,” Mr. McIsaac said.
“For smaller production, we recommend our Vemag 500,” he continued. “For higher production, we step up to our HP series. In either case, our engineers and bakery specialists work directly with the customer to tailor the machine setup to their needs.”
Screw augers cue productivity for Unifiller’s Uni-X system, Mr. Macpherson noted. “This is an intermediate-level machine with its own conveyor belt. It uses a screw auger instead of conventional rollers to deliver dough. Another new unit is the Uni Dopositor. One infeed roller is set at an angle, higher than the other, and both are independently controlled via servo motors.”
Because gluten-free doughs are subject to rapid shifts in density, Unifiller added to its computer controls a feature that allows changes to be made on the fly. “The operator can run a check sample and then tweak settings up or down,” Mr. Macpherson explained. “We use a color touch-screen terminal with icons, rather than English-language words. The operator hits an icon and can make up or down changes in partial grams or ounces. The speed of filling is also adjustable, whether you’re working with multiple deposits per row or one single deposit.”
Servo control of the ram enhances gentle handling of delicate doughs.
Piston, drum, ram
Piston dividers coupled with drum-style rounders have long been workhorses in producing conventional rolls. Now, the method has been adapted to high-absorption conditions. Design changes by WP Bakery Group engineered the Tewimat Soft specifically to handle doughs with 70 to 80% absorption, according to Patricia Kennedy, president. “Clearly, the problems of gluten-free products involve sticking in the pistons and divider area,” she noted.
Olaf Oertelt, export sales manager, WP Bakery Group, explained the changes to the machine. “The dough is cut straight into the central rounding drum,” he said. “We added flour dusting capability and a driving roller that ensures the release of the dough pieces into the drum.” The company won an award for innovative technology at iba 2015 for this machine.
“Accuracy in scaling while maintaining the integrity of the dough are the essential aspects,” Ms. Kennedy said. “The Tewimat Soft is already a very successful design even though the machine was released only in the past couple of months. Previously, people could not automate such doughs, but this divider provides the accuracy and gentle touch needed.”
Ram-and-knife methods haven’t been left behind; they have been enhanced with servo drives and drag-reduction methods, according to Mr. Graham. “The main driver for development of the servo ram was to improve the crumb structure of standard bread without sacrificing scaling accuracy,” he said. But it also pays dividends when scaling gluten-free doughs.
“Some compression of the dough is inevitable but is minimized by long, slow stroke of the ram,” Mr. Graham explained. “The gentle handling of the dough in the Accurist2.1 divider is enhanced by servo control of the ram, which stops the forward motion when a set pressure is achieved, rather than over-pressuring by advancing to a fixed position, which cam-driven dividers do.”
Mr. Graham reported an unexpected benefit. “Customers buy our dividers with the expectation that they will achieve good scaling weight, better bread quality due to minimum dough damage and easy cleaning/rapid changeover,” he said. “What they are not necessarily expecting, and often comment favorably on, is that there is zero temperature rise in the dough as it passes through the divider. This makes it much easier to handle through the rest of the process.”
Another manufacturer engineered a reduced-stress feature for its dividers. “This makes dividing more gentle on the dough,” explained Patrick Harp, sales application engineer, Gemini Bakery Equipment. “The Voluminator controls the divider’s action for delicate or dense doughs by limiting the mechanical force exerted by the machine.”
The company also recommends use of a Dough Preportioner, essentially a large hopper and chunker placed above the supply hopper of the divider. “The Preportioner can hold a full dough from the mixer,” Mr. Harp said. “Scaling accuracy of the divider is proportional to the size and weight of the dough chunk. A properly sized dough chunk will ensure an even distribution of dough across the weidth of the divider.”
Mr. Harp continued, “Gemini offers a range of versatile dividers with optional features to meet the most demanding applications.”
Engineered to handle sticky materials like caramel, these coextruders handle gluten-free doughs with ease.
The whole package
While a baker may buy a depositor or divider to handle a specific product, the purchaser should be looking at versatility, too. The quick-moving consumer market demands such flexibility.
“The trend toward stickier and gluten-free products is part of a broader trend toward rapid product development and broader product ranges,” Mr. Graham observed. “The effect of this is shorter production runs and product life cycles, meaning that dividers need to be capable not only of increasingly rapid changeovers but also adaptation to new products.”
Dedicated lines are traditionally more efficient and easy to run, Mr. Zelaya noted, but you need to think ahead to the next big new product. “As the gluten-free and non-traditional breads market continues to grow and expand bakers’ product portfolios for their customers, flexibility on the equipment capabilities is a great asset,” he said.