March 19, 2013
by Shane Whitaker
Have you ever wondered why bread and dough are popular slang for money? One thing is certain: To make steady profits, bakers and snack manufacturers must first create consistent dough. Pun intended.
Dependable doughs come from the mixing process, and bakers rely on their mixers to make the same quality dough batch after batch or through continuous mix cycles.
“If you ask bakers to list their top goals for mixing systems, the list will be very diverse; however, the No. 1 goal of nine out of 10 bakers would be make the same dough all the time,” said Jim Warren, director of mixing sales, Reading Bakery Systems, Robesonia, PA. “Consistency is the No. 1 goal. The entire process depends on this.”
Bakers strive for consistency in time and temperature. “If they can get optimum dough development at the right time and on target for the temperature their process is designed for, then the mixer has done its job,” said Bruce Campbell, executive product manager, dough systems, AMF Bakery Systems, Richmond, VA.
Keith Graham, marketing manager, Baker Perkins, Grand Rapids, MI, noted cookie and cracker manufacturers need consistent dough properties. “This is achieved through good dispersion of ingredients, homogeneous formation of dough and, where appropriate, fast and uniform development of gluten,” he said.
Bakers also want rapid mixing and efficient discharge, Mr. Graham noted, pointing out that the company’s High Speed (HS) multipurpose batch mixers feature a unique blade design that imparts faster mixing and dough development along with minimized cleaning costs.
“A shaftless blade ensures thorough mixing through good dispersion and rapid dough development because there is nothing that prevents the ingredients or dough from circulating freely around the bowl,” he explained. “Having no shaft also eliminates a static point where the dough can hang on discharge and debris can build up.”
At the end of mixing, the bowl almost completely inverts for fast, fully automatic discharge. “As well as not having a shaft, the mixer has no other ‘dead’ spots where debris can accumulate, so no operator assistance is required to remove the dough from the bowl,” Mr. Graham added.
Other primary issues in mixing include changeover time and labor reduction, Mr. Campbell noted. AMF has focused on three areas to optimize its traditional horizontal batch mixers that range from 400- to 3,200-lb capacities.
First, it employed Finite Element Analysis (FEA) to develop a new bowl design. “We measured the actual shock load in a production mixer to determine the live forces that are impacted on the bowl during the mixing process,” he said. “We then used FEA to enhance our bowl structure and welding to ensure infinite fatigue life for the cooling jacket.”
As its second step, the company used a lab mixer and changed variables such as agitator design, bowl shape and glycol flows. The result? Overall mix time dropped by 10 to 20%. “Third, we have increased the efficiency of the cooling circuit so cooler dough temperatures are attainable on a consistent basis with less energy demands on the glycol system,” Mr. Campbell added.
To help bakers achieve cooler dough temperatures, Shaffer-Bundy Baking Solutions, Urbana, OH, introduced a refrigerated agitator that decreases final dough temperatures by 6 F°, according to Terry Bartsch, vice-president, sales.
Variable frequency drives (VFDs) continue to push improvements in mixing and lend themselves to new technological features in the equipment. “They enable the design of direct-drive systems and open-frame mixers,” Mr. Bartsch said. “They also provide a built-in soft start, a more efficient transfer of energy and the ability to program an automatic discharge sequence for a fully automated system.”
Additionally, VFDs can run at any speed to customize proprietary products and allow bakers to mix multiple products on a single machine, he noted.
OEMs adopted VFDs because bakers wanted higher levels of control, according to Mr. Graham. “The ability to select mixing speed at-will means that a mixing profile can be developed to match the characteristics of each type of dough,” he said.
This type of motor improves working conditions, with less noise and vibration as the machine starts up and changes speed. “This also reduces maintenance requirements,” Mr. Graham observed. “An additional maintenance benefit is the use of an off-the-shelf motor rather than the special unit required for two-speed mixers.”
Focusing on safety
VFDs eliminate mechanical parts such as belts, chains and sprockets, Mr. Bartsch said, decreasing maintenance requirements and failure points. He also pointed out that they allow safer operation, using an emergency stop to kill power to the motor.
Ensuring employees work in a safe environment and equipment designed with the latest safety features are some of the greatest concerns for bakeries, Mr. Bartsch added. Mixer features now include new bowl seal materials and designs that eliminate up to 99% of flour leaks during mixing. Two-way tilt systems and employee platforms keep employees from having to stretch to add ingredients through doors or over dough handling equipment in front of the mixer.
Mr. Bartsch added that placing ports for Ethernet connections and 120-volt outlets on the outside of electrical panels keeps panel door closed at all times, thus protecting employees from arc
To minimize arc flash concerns, Topos Mondial Corp., Pottstown, PA, designs panels on its mixers with all Touch Safe components.
Mixing to energy
Advance Food Systems’ high-speed mixing systems also feature VFDs. Denny Vincent, president of the Columbus, OH-based equipment manufacturer, described the company’s ABM mixing systems as somewhere between continuous and horizontal mixing systems. The high-speed batch mixers’ processing tools rotate at 200 to 1,200 rpm. A slower-moving scraper bar, running at 24 rpm, moves in the opposite direction and keeps ingredients in nearly constant contact with the main mixing tool.
Available in three sizes, 350, 1,000 and 2,000 lb of finished dough per batch, ABM mixers use various tools to create batters as well as short and developed doughs. Batch mixing times typically range from 30 seconds for donut batter to a little more than 3 minutes for saltine dough.
However, the high-speed machines generally mix to energy, rather than operate on specific timed cycles, Mr. Vincent noted. “The cumulative energy that goes into a dough is a true indicator of the development taking place in the mixer,” he said.
The ABM’s mixing tool is its motor shaft with no transmission or anything between. Thus, when the PLC reads the amperage or kilowatt energy load on that motor, it knows exactly what is taking place in the mixer, Mr. Vincent observed.
Mixing to energy also allows a bakery to adjust mixing times as it receives new crop flours. “If your new flour is a strong flour, it might take 15 to 20 seconds less mixing on a 2-minute mix because a stronger flour develops more quickly than a weaker flour,” Mr. Vincent explained.
Undoubtedly, consistency and repeatability in mix and process represent the greatest challenges for bakers and snack manufacturers. Because the high-speed mixer makes smaller and more frequent doughs, Mr. Vincent said that many bakers believe they get greater control throughout the process. “It’s not continuous but about as close to it as you can get in terms of controlling the variance in your doughs during machining,”
The high turbulence in the ABM mixers increases absorption rates, according to Mr. Vincent. “When we do a test at a bakery, we start using its formulation. When the dough discharges from our mixer, it typically feels dry and tight to them,” he said. “So we then will add 3 to 4% more water and mix. We continue to add more water until the dough feels more like what they are used to and want to run down the line.”
Another relatively new mixing system also allows for increasing the water levels in doughs. Rapidojet mixers increase hydration levels of flour yet maintain the same dough characteristics, according to Ken Schwenger, president of Bakery Concepts International, LLC, Mechanicsburg, PA. The mixer’s gentle mixing physics typically raise water levels by 5 to 10%. “Rapidojet creates a homogeneous product by eliminating free water and increases existing sensory attributes such as volume, taste, aroma and shelf life,” he said.
Bernhard Noll, PhD, a food technologist from Schwabisch Hall, Germany, invented the Rapidojet technology in 2002. The mixer injects water at high pressure into freefalling dry ingredients. Other ingredients can be dissolved in the injected water, and the system can be used to prehydrate ingredients or as a final mixer.
Rapidojet also offers energy savings because it generates virtually no friction; the dough temperature is controlled by the temperature of the incoming water.
Because Zeppelin System USA’s core competency is raw material and ingredient handling, the company’s Codos continuous mixing and kneading systems offer fast changeovers and compensate for raw material quality fluctuations, according to Stephen Marquardt, sales director, food for the Odessa, FL-based supplier. The company can install fully automated sponge-and-dough systems as part of the Codos line, which produce consistent dough quality and dough temperatures for a variety of fresh and extended-shelf-life baked foods.
AMF has been working with Reading, which is a member of the Markel Bakery Group with AMF, on adapting the Exact continuous mix system for bread and buns. “To date, we have been successful making some very high-quality buns in our lab and will be taking this technology to a production line in March,” Mr. Campbell said.
The continuous mixing system underwent some minor modifications to the standard design elements to process highly developed doughs like buns and English muffins, Mr. Campbell noted. “But we have been successful and are ready to roll this technology out to bun producers,” he added. “The advantages of continuous mix for bakeries that have large runs of similar doughs are primarily consistency and labor cost reduction, which are two of the main ingredients to a more profitable bakery.”
Making bread — aka money — always begins with developing a consistent dough, and mixing technologies today feature designs that ensure dependable dough batch after batch and throughout continuous mix cycles.