Getting into the mix
October 1, 2012
by Shane Whitaker
Mixing isn’t magic. Like most steps in baking, it involves science, yet sometimes it benefits from an artistic flourish. Today, bakeries employ a variety of systems to hydrate as well as to knead dry and wet ingredients, forming doughs that can be used to make sundry baked foods and snacks.
Both batch and continuous dough mixers can develop dough to suit bakers’ needs, and original equipment manufacturers (OEMs) continue to improve their mixers’ capabilities and designs to meet their customers’ requirements. They work to make their mixing equipment safer and easier to clean and maintain. OEMs also look for ways that bakeries can reduce energy usage and mix times. Often, these flexible systems permit bakers and snack manufacturers to frequently expand their product portfolios.
Sealing in sanitation
Reducing sanitation and maintenance time drives many of the advances Shaffer Manufacturing, a Bundy Baking Solutions company, makes in mixing technology, noted Terry Bartsch, vice-president, sales, of the Urbana, OH-based OEM. For example, the company recently focused on improving its bowl and shaft seals. Its new seals reduce the amount of flour dust escaping from the bowl.
“We removed all the sealing components from the underside of the canopy, and they are now mounted to the top of the canopy,” Mr. Bartsch noted. “So we have a very clean underside.”
Another issue bakeries have with older seal designs, he said, is flour collecting along the top ledge of the mixing bowl, and when the bowl is tilted forward to kick out dough, this flour would fall onto the mixed dough. To eliminate this problem, Shaffer uses a flexible material mounted to the bowl. When the bowl moves under the canopy, the bowl seal is under pressure. “As flour is dumped into the bowl, air displacement creates even more pressure and a tighter seal against the canopy,” he added.
Whereas many mixers feature front and back seals from a rubber material that degrades over time and use ultra-high-molecular-weight polyethylene (UHMW) on the sides, Shaffer manufactures the front and back seals from UHMW, and the sides seals are a polyurethane material.
AMF Bakery Systems’ tilt and overtilt bowl mixers feature high-quality sealing systems to keep the dough in the bowl and the interior of cabinets clean, according to Bruce Campbell, executive product manager, dough processing technology, for the Richmond, VA-based equipment manufacturer.
Mr. Bartsch pointed out that open-frame horizontal mixers inherently are easy to sanitize because there is less surface area and the supporting structures are much smaller.
To improve sanitation on its mixers, Topos Mondial Corp. eliminated as many fasteners as possible because they can harbor bacteria and pathogens, according to Damian Morabito, president of the Pottstown, PA-based company.
Going to direct drives
Topos Mondial manufactures open-frame horizontal mixers in single- and double-sigma styles as well as 3-roller-bar mixers with 800-lb capacities or less. However, Mr. Morabito said he’s not yet convinced that a direct-drive gearbox would hold up over time in a larger open-frame roller-bar mixer.
Mr. Bartsch noted Shaffer’s open-frame design allows direct-drive technology to be used on horizontal mixers. “Direct drive has been a big factor for Shaffer and in what we have done over the past couple of years,” he said.
Direct drives reduce maintenance by eliminating components such as pulleys, chains and idlers. “Your drive now is just your gearbox and motor,” Mr. Bartsch noted. “We eliminate the couplings between the motor and the gearbox and the overhung load from the output shaft of the gearbox.”
All of Shaffer’s direct-drive mixers feature variable-frequency drives (VFDs). “VFDs made direct drive doable,” Mr. Bartsch said. “The startup torque on a 2-speed motor would cause the gearbox to chew itself up. With a VFD, we are able to do a soft start where you ramp up speeds, and it is a lot smoother on the gearbox.”
AMF also developed a small line of direct-drive mixers that are simple and easy to clean, Mr. Campbell said.
When redesigning its open-frame mixers, Shaffer wanted to drive out the need for greasing as much as possible. By using a composite material at the pivot joint for tilting the mixer bowl up and down, the company eliminated a major grease point that often fuels a constant battle between maintenance and sanitation crews. “Maintenance would grease the bearing, but during cleaning, they would hose away all the grease. And then maintenance would have to come back to grease it again,” Mr. Bartsch explained.
To further reduce maintenance, Shaffer remotely mounts hydraulic units for the mixers’ tilting systems. “We’ve removed this component from the mixing area that would need to be cleaned on a regular basis,” he said.
Topos installs self-contained hydraulics packages to operate its overtilt bowl assembly, and as an option, it offers a hand pump. “If you lose power to the mixer for any reason, this option gives you the ability to manually pump the hydraulics to discharge the dough,” Mr. Morabito explained.
Shaping the bowl
To help bakeries achieve the dough characteristics they desire from the mixer, Topos focuses on the science of kneading. “The key to our designs is that we configure the bowl to properly knead,” Mr. Morabito said. “It is important to get the bowl set for changes based on absorption. A stiff dough kneads differently than a soft dough, and the bowl needs to be configured appropriately for the absorption of the dough. The RPMs need to be adjusted to get the proper kneading.”
Topos’ roller-bar mixers feature a D-shaped bowl, and the bowl’s flat surface improves the kneading action of the dough, he said. To get the proper kneading action, positioning of breaker and roller bars can be reconfigured “We are reducing mix times, which increases throughput per hour,” Mr. Morabito said. “We also are dramatically decreasing the cooling load needed on the bowl. When you are properly kneading, you are not overheating the dough.”
Shaffer also engineered an exclusive bowl shape for its roller-bar mixers, known as its Superbowl design that features a curved back to impart less deflection to the bowl sheet, according to Mr. Bartsch.
In fact, the company did a finite element analysis (FEA) comparing the older and newer designs. “We had much less deflection in our bowl sheet compared to the U-shaped bowl,” he said. “During the last stages of mixing when you get a lot of dough development, you get a lot of violent action as the mass of the dough hits the back of the bowl. Anytime you can have less deflection in the back, you extend the life of the bowl, the jacket and the other components.
“We have a unique bowl shape for our yeast-raised dough customers that we believe is stronger and, in some cases, has shortened mix times,” Mr. Bartsch continued.
According to Mr. Campbell, one of bakeries’ biggest concerns as it relates to mixing is getting consistent dough development in the minimum amount of time. To this end, AMF offers several styles of agitators to match the requirements of specific dough.
AMF’s single-point integrated controls ensure the entire mixing and makeup system runs accurately on fresh dough.
Improving continuous mixers
Continuous mixing systems have benefited from recent developments designed to give them greater flexibility, make them easier to clean and enable more opportunities to monitor mixing.
The Exact Mixing FX2 continuous mixer from Reading Bakery Systems, Robesonia, PA, provides the versatility that permits manufacturers to make baked potato, corn, wheat and multigrain crisps using the company’s Multicrisp line, according to Jim Warren, director, Exact Mixing.
“Now, the snack manufacturer doesn’t have to invest in a new line that only makes one type of product,” he said. “This reduces the risks of adding a new line and increases the chances the new investment will be a big hit quickly.”
The Codos continuous mixing and kneading system from Zeppelin Systems USA, Odessa, FL, provides consistent dough quality and dough temperatures. The preparation, handling and continuous feeding of raw materials to the mixers represents the most important factor of a highly functioning continuous mixing system, according to Stephen Marquardt, sales director, food, North and South America. He pointed out that the company’s core competency is raw material handling and ingredient preparation. Its fully automatic mixing systems feature fast recipe changes and immediate compensation of raw material quality fluctuations.
Zeppelin recently installed its first fully automated sponge-and-dough system with Codos for the production of rusk with a 4.5-hour continuous fermentation time.
Invented in 2002 by Bernhard Noll, PhD, the Rapidojet continuous mixing system is revolutionizing the doughmaking and hydration process, according to Ken Schwenger, president of Bakery Concepts International, LLC, Mechanicsburg, PA, which represents the technology in North, Central and South America. The Rapidojet shoots high-pressure water into a free-flowing stream of dry ingredients, hydrating them instantaneously.
Bakeries using Rapidojet can adjust hydration and recipes via PLCs, and these changes occur almost immediately. It can run doughs from 10% to more than 350% hydration, Mr. Schwenger said.
Because the Rapidojet creates a homogenous mix with higher hydration levels — 8 to 10% more water must be added to achieve the same dough consistency — it increases product quality and softness, reduces ingredient costs, and imparts a longer shelf life and better volume and strength to baked foods, Mr. Schwenger said.
The technology also eliminates heat created from mechanical force, thus bakers controls dough temperature solely via incoming water temperature. They can also significantly reduce yeast and dough conditioner requirements with the mixer because Rapidojet doesn’t generate the friction and heat that can affect gluten structure, Mr. Schwenger said.
Using Rapidojet as a pre-mixer to produce a sponge or to hydrate minors such as bran, rice flour or whole wheat flour prior to adding them to the final dough mixer can reduce overall mix time. “We cut the final mix time in a large horizontal mixer for bran bread by 20% just by introducing fully hydrated bran,” Mr. Schwenger observed.
Rapidojet is easy to disassemble and clean, and doors are completely sealed for exterior washdown.
Reading’s customers report cleaning times on its new Exact mixers have been reduced by as much as 70% compared with sanitizing mixers built as recently as five years ago, Mr. Warren said. The mixer’s clamshell design not only improves the ability to clean the unit but also to inspect it after cleaning.
Monitoring the process
One of the greatest challenges in mixing remains the diligence of operators. “The quality seldom suffers when the production manager is in the mix room,” Mr. Warren said. “That’s because everyone is on their toes. But it’s difficult to maintain that intensity level 24 hours a day.”
If an issue arises in mixing, often it isn’t even detected until the packaging line by a quality control operator or system, which can lead to a lot of wasted product, Mr. Warren added. “Our control systems monitor all aspects of the mixing system 24 hours a day,” he said. “Problems are detected immediately and not repeated. The process can be monitored anywhere in the plant, including the QC department or in the production manager’s office.”
Lots of improvements are being made to mixing systems. Equipment manufacturers work with their customers to ensure that these systems not only create the doughs they desire but also are easily cleaned and maintained, versatile, and robust enough to last a long time.