Food Engineering

Tech Update: Mixing and Blending

February 1, 2010
Complete knowledge of your process and product can improve quality and yield.

In this pizza dough application, the ABM 1000 can produce up to 1,000 lbs of finished dough in 30-50-lb. chunks in one to three minutes. Source: Advanced Food Systems.


Given the variety of mixing/blending equipment options available to food processors coupled with seemingly endless combinations of food and beverage applications, selecting the right equipment can be a challenge. Processors can, however, choose equipment that accomplishes their goals with the proper planning.

According to Denny Vincent, president of Advanced Food Systems, most customers know what their finished food product should be, but may not know how to produce the desired results on a large scale. This is especially true if they used a test kitchen mixer, such as a small Hobart, to make something like puff pastry dough. While mixing the dough on a test mixer may take eight to ten minutes, the mixing process on an industrial mixer will take about two minutes. While this is exciting news for the processor, it means some consultation will be needed to set up the process.

Because quickly scaling up is key to competing successfully in the market, “the old analogy of scaling from a Waring blender or food processor in the lab no longer cuts it,” says Pete Leitner, Admix vice president of sales. Many suppliers are investing in test kitchens, labs, or pilot plants staffed by industry-experienced food scientists or quality assurance personnel. State-of-the-art equipment in these facilities is critical to help processors set up and validate a process, says Leitner.

“The key to solving a mixing problem is to know the product-the viscosity, density, shear sensitivity-and also to know the process,” says Mike Terry, Anderson Dahlen project engineer. Terry says he worked with one processor that wanted to use the same equipment to blend cinnamon into peanut butter in one application and whip a light, watery product in another. “You have to work very closely with the customer to see what the final outcome is-whether he wants to suspend solids, mix powders into a liquid, or homogenize a product,” says Terry.

“More than 80% of the time, our customers require a test on their product or request a reference that has used our equipment on a similar product,” says Daniel Osiedacz, Fristam Pumps blending/mixing product manager.

(Left): Munson’s Model 700 rotating drum with proprietary mixing flights achieves total batch uniformity in less than three minutes at Pro-X Nutraceuticals. (Right): Internal mixing flights elevate the material, which is discharged through a plug gate valve into plastic-lined drums. Source: Munson Machinery

Meeting application needs

Food processors require mixing and blending solutions that provide economy of scale, according to JD Larson, DCI Inc. sales engineer. This equipment should accommodate increased working volumes and reduce batching time, stand up to increased production cycles, and provide maximum cleanability (with verifiable, CIP-ready designs). Robust designs that decrease maintenance time and deliver specified performance and commercial requirements within a restricted project budget are desirable.

Increasing throughput is a reason processors upgrade mixing equipment. Pro-X Nutraceuticals (Irvine, CA) was founded in 2004 as part of Roex, a manufacturer of vitamins, dietary supplements and herbals. Production Manager Kory Seitz realized that the company’s only mixer, a 30 cu.-ft. ribbon blender, became a bottleneck due to its small size. Batches had to be split up, requiring extra labor for feeding, weighing, discharging and cleaning.

After considering V-blenders and rotary batch mixers, the company installed a 110 cu.-ft. Model 700 TS 110 stainless steel rotary batch mixer from Munson Machinery. Where the original ribbon blender had a capacity of 1,741 lbs, the new rotary batch mixer handles up to 5,358 lbs, tripling mixing capacity. The company also realized the unexpected benefits of reduced labor, shorter blending cycles, ease of cleaning and minimized waste.

“Think of the productivity gains in being able to mix once versus three times,” says Seitz. “Not only are we mixing fewer times, but we’ve also reduced labor for weighing, screening and staging prior to mixing. “When running several batches to fill a single order, we were performing these tasks several times. Now those tasks are done only once.”

With no moving parts inside the mixer, it’s capable of achieving 100% uniformity in less than three minutes, although Seitz runs the mixer for longer cycles for absolute insurance of uniform blends. The mixer discharges 5,358 lbs of product into about 20 plastic-lined drums, with each drum receiving 241 to 321 lbs of powder. While the mixer takes about 20 seconds to fill each drum, only 17.5 oz are left behind, making waste negligible and cleaning an easy task.

Similarly, Gewuerzmueller GmbH, a premium mixed herbs producer, wanted to increase its marinade production. Johann Rimboeck, technical CEO, designed the plant, which consisted of a FrymaKoruma MaxxD 1300 vacuum processing plant that can prepare up to 15 tons of marinade per day. (FrymaKoruma is the processing division of the international Romaco Group.) Four tanks, each about 20 ft tall and weighing 5.3 tons, were installed in the headquarters plant in Korntal-Münchingen, Germany.

Using the PAS 4 recipe/automation system-part of the MaxxD 1300-oil is mixed with spices, and the mixture is then suspended using a special emulsifying process developed by Gewuerzmueller technologists. Remaining in suspension, 15 tons of the marinade is produced daily. According to Rimboeck, the versatile unit will also be used to produce salad dressings in the future.

Improving yield and decreasing ingredient costs

Creating and maintaining a consistent product while using less of its expensive ingredients can improve yield and save money, but it presents a challenge for the mixing process.

According to Vincent, mechanical mixing action (mechanical hydration) during the dough-making process can be intensified to expose more surface area of the flour particles, enabling the flour to absorb more water and increasing the hydration rate. Since this moisture is “bound up,” sticking can be controlled and shelf-life is not reduced. The increased absorption equals higher yields using less flour and saving ingredients.

Vincent also recounts early experiments with mixing pie dough under vacuum. While the meat industry has used vacuum mixing for some time, Vincent’s company applied it to mixing flour, water and shortening. Under vacuum, trials found that 20% of the shortening used in standard atmospheres could be substituted with equal parts of water and flour in high-speed mixing under vacuum. Not only did the pie maker save on fats, the pie could also be promoted as having a lower-fat crust.

Gary Barber, general manager for Ross Systems and Controls, says that mixing vessels can be designed for vacuum applications with an extra port in the hood. The vacuum can be controlled using a vacuum transmitter, automated valves and a pump. An advantage to mixing under vacuum, Barber says, is the process keeps the air out, preventing contamination.

In this batter application, an in-line, high-shear mixer was added between the batter mix unit and the enrobing system to remove lumps in the batter, which caused an unsightly product appearance and tended to jam the packaging equipment. Source: Silverson.

High- and low-shear applications

High-shear mixers can make lumpy slurries more fluid. For example, a processor of fish fingers and chicken nuggets had problems during preparation of the batter mix, where flour and other powdered ingredients were forming lumps that the existing mixing equipment couldn’t break down. These stuck to the product in the enrobing stage, resulting in an unsatisfactory appearance, and in some cases, misshaped or oversize products that couldn’t be packaged. A Silverson in-line, high-shear mixer was installed between the mixing vessel and the enrobing unit, smoothing out the batter and solving the enrobing problems.

Often it makes sense to offer separate products for low- and high-shear applications, says Ken Langhorn, Charles Ross & Son Company technical director. Langhorn suggests a tool that is very gentle but provides efficient and thorough agitation for mixing vegetable soup where the potatoes and carrots should not be reduced in size. If a processor is making a sorbet where the product really needs to be ground, Langhorn would recommend an entirely different high-shear tool.

For a sauce product, a processor receives the primary whey ingredient in 20-kg frozen blocks, says Larson. In the past, significant time was needed to reduce these blocks to chunks that could be introduced into a standard food processing vessel. “To limit this up-front prep time, we demonstrated a processing vessel that also had high-shear capability,” adds Larson. This dual-agitated equipment broke up and dissolved the frozen commodity ingredient blocks directly, saving time  and limiting the potential for error and external contaminants. After this dissolution, the system functioned as a standard processor to complete the product. Since then, the system has also been used by a confectioner to reduce similarly sized commodity blocks of chocolate and butter.

Toward more green mixing

As is the case with most process equipment, energy use is under scrutiny in mixing technology, says Jim LeClair, SPX Flow Technology product manager. A critical aspect of mixer development involves finding wasted energy within the mixing process.

At the same time, LeClair says mixers must be able to handle variable product viscosities. “The goal is to be able to provide enough energy within the process to meet the customer’s final product composition requirement,” adds LeClair.

Often capable of using less energy, static mixers are inline systems (typically inside piping) with no moving parts where ingredients will be injected, and the components will be swirled and mixed within the interior of the piping. The flow itself provides the motive force to do the mixing. Terry says that for some limited applications, static mixers have actually replaced batch mixers, but he cautions processors to examine applications thoroughly before committing to a choice.

An inherently low user of energy, a mixer using a gas bubbling technique is suited especially for large tanks of liquid, such as oil or wine fermentation systems. According to Dick Parks, Pulsair Systems’ owner, the power requirements in a 100-ft. diameter tank are as low as 0.0060 hp per 1,000 cu.-ft., which is a fraction of what mechanical mixers use. He notes that to reduce trans-fat levels, a potato processor mixed two oils with inert nitrogen bubbles, using approximately $50 worth of nitrogen, which saved $5,000 in off site mixing. Nitrogen is also used in 300,000-gallon wine tanks to mix wines in 10 to 15 minutes. Parks has also installed these bubbling systems in rail tank cars of chocolate to eliminate the heel when the chocolate was drained from the cars. Likewise, one corn syrup customer used the mixing system with heat applied to rail cars of HFCS to reduce the time necessary to heat and drain the cars.

Another use of gases is for cooling product as it’s being mixed mechanically, says Vincent. When flour and sugar are coming from outdoor silos in the summertime to make cookie batter, for example, the batter will be too warm to send down the line for forming and baking. Carbon dioxide or nitrogen can be injected into the mixer bowl to bring the temperature down to the 55 to 60°F needed for further processing.

When the application calls for mixing powder into liquid while viscosity changes, Terry says mechanical blending, rather than gas, can provide the horsepower to get the job done. In addition, heating and scraping the side of the tanks to prevent caramelizing is better suited to mechanical systems.

CIP funtionality

To meet regulatory specifications, processors are looking at clean-in-place functionality for several reasons. Eliminating allergens from products is very important, says Leitner. But from a design standpoint, a mixing system must allow for quick changeovers from one recipe to the next.

Knowing that food safety is critical, suppliers are designing mixers and blenders to be more CIP compatible since this provides two advantages, according to LeClair. First is the ability to have confidence that the unit is completely clean after the CIP cycle. Second is the ability to shorten cleaning times through CIP automation, facilitating more processing capacity and requiring less time in the cleaning cycle while providing the processor with a better return on investment.

In the future, processors may have access to one-time use “throw-away” mixers that can be used in small applications where contamination risks are high and cleaning is not always a viable option, says Richard Adams, SPX Flow Technology product manager. Presently, however, units and materials that can withstand CIP solutions are part of the design in his company’s LIGHTNIN mixers, and also meet ASME-BPE design specifications and 3-A standards.

Automation eases the process

Automation varies from completely automated batches to totally manual batches, where chefs still want the personal touch. But for processors concerned with FDA’s 21 CFR Part 11 recording of data, Barber suggests implementing a PLC-based data acquisition system. Barber has seen these applications expand from manual additions of ingredients to tracking of silo levels for ingredients. Barber will automate the mixing process-including vacuum systems if necessary-but he will call in local system integrators for integrating the larger-scale system.

Other benefits to automation include the more obvious. According to Barber, the use of icons on touch screens makes it easy for operators who may have trouble reading, and automation can guarantee weigh and mix consistency every time while ensuring that batch and CIP records are kept whether or not operators remember to take readings.

For more information:
Denny Vincent, Advanced Food Systems, 614-939-0011, dv@advancedfoodsys.com
Mike Terry, Anderson Dahlen, 763-852-4700, term@andersondahlen.com
Daniel. Osiedacz, Fristam Pumps, 608-831-5001, dosiedacz@fristampumps.com
Pete Leitner, Admix, 603-627-2340, pleitner@admix.com
JD Larson, DCI Inc, 320-252-8200, jdlarson@dciinc.com
Gary Barber, Ross Systems & Controls, 866-797-2660, gbarber@rosssyscon.com
Jim LeClair, SPX Flow Technology, 262-728-4912, jim.leclair@apv.com
Ken Langhorn, Charles Ross & Company, 631-234-0500, klanghorn@mixers.com
Dick Parks, Pulsair Systems Inc, 425-455-1263, dickp@pulsair.com
Richard Adams, SPX Flow Technology, 585-527-1937, richard.adams@spx.com
Steve Knauth, Munson Machinery Company, 315-797-0090, info@munsonmachinery.com
Brian Martin, Silverson, 413-525-4825, bmartin@silverson.com
Mike Starer, Romaco FrymaKoruma, 973-709-0691, mike.starer@romaco.com