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Adding Ingredients Under Vacuum Prevents Air Inclusion

Aug. 20, 2007
Adding ingredients under vacuum and other solutions to mixing and blending challenges.

Air is great stuff for breathing and inflating basketballs, but a genuine nuisance when you are adding dry powder to a liquid. More and more powders are entering the food processing mix, a by-product of delivering more nutrient- and flavor-packed products to the health-minded masses. Beverage formulations in particular are becoming more complex.

"We are able to reduce the air in our mix by going to equipment that brings powder in under the liquid via vacuum," says one processor whose company has profited from a co-packing relationship to produce a major brand of isotonic beverage. The equipment is of recent vintage, he notes, and he wonders why the solution took so long to come to the fore.

Admix's VacuShear provides vacuum conveying and blending of dry ingredients without aeration and foam (in partnership with A&B Process Systems).

Reducing the amount of air that enters the mix may not sound like a Nobel Prize-worthy accomplishment, but don't tell processors that. The latest generation of mixers is answering some of the longest running nuisances in processing.

The challenges of mixing are as familiar to the kitchen counter chef in your home as they are to the processor of mass quantities of food and beverage products. Traditional mixing incorporates air into the powder/liquid mix causing foaming, clogging and lumps. If the ingredients contain fat, separation of that fat can be a problem as well.

Difficulties with drinks

Always an issue in beverage mixes incorporating powders, solubility has become a more serious challenge as processors attempt to add a wide range of complex ingredients such as aspartame and other sweeteners, vitamins, minerals, amino acids and new waves of healthful ingredients into small quantities of liquid.

"In some nutritional drinks, such as isotonic beverages, it is often difficult to dissolve the ingredients," says Jean Pierre Berlan, director of sales and marketing for Tetra Pak (www.tetrapak.com), Vernon Hills, Ill. "Today's beverages are more and more complex, and you need different techniques to incorporate powders."

Improving the shear rate may have been sufficient with more traditional mixing applications but shear rate alone may not be enough with today's complex beverages, which have inspired entirely different design approaches. Ingredients such as carboxy methyl cellulose (CMC) change the thickness and mouthfeel of a mixture and can be difficult to dissolve in water. Maltodextrin, sucralose, aspartame and other complex carbohydrates and sweeteners are putting equipment and mixing talent to test. Creating a vacuum keeps air entry to a minimum.

"Our Flex Mix Instant draws powder under the liquid via vacuum," explains Jim LeClair, regional product director for Lake Mills, Wis.-based APV/Invensys (www. apv.com). "It actually minimizes the amount of air that enters the mix."

Like everything, the improvement comes at a price, he notes. The mechanical and automation systems are more complex and, correspondingly, more costly. The latest generation of equipment represented by Flex Mix requires a better educated operator due to the demands of the vacuum system and automation additions. "But the total cost of ownership is less because there is less operator intervention," LeClair adds.

"A good way to deal with air and clogging is with a vacuum high-shear mixer," agrees Berlan. "It is the new name of the game when you are dealing with highly complex ingredients."


Tetra Pak's answer employs bottom-of-tank entry which, when coupled with vacuum, radically reduces air intrusion in the mix. European processors have used such systems more than their American counterparts. "It is far more effective with difficult powders," says Berlan.

When uniformity and getting all the air and fisheyes out is paramount, sometimes multiple passes are necessary. This Admix Fastfeed powder induction system allows the gradual, manual addition of powder into a liquid stream. Blue arrows represent liquid flow into the system. Green arrows represent mixed product flow, powder and liquid, back to the source tank. Processors continue the blending until they're satisfied with the batch.

High-shear mixing under vacuum today has clear advantages. Such systems help dissolve more of the ingredient mix in small quantities of liquid and enable the processor to avoid "fisheyes" in the mix. "A lot of water might not be what you want in your recipe today," says Berlan. "With the demand today for these products, recipes will become more and more complex." 

Floor-loaded Admix Fastfeed mixers also are designed to take in powders or liquid under vacuum. The high-shear mixers disperse powders effectively, and they allow quick changeover and blending accuracy.

The valves on the powder hopper allow you to monitor the amount of powder that goes into the liquid," says Keith Cheries, national sales manager for based Admix Inc. (www.admix.com), Manchester, N.H. "It's easy to change and adjust. Some powders go in easy; some are more difficult. But with our system, it is easy to change powder feed rate."

"The biggest need in the industry today is on-the-fly mixing or high-shear mixing," he adds, noting that his company's Fastfeed mixer incorporates powder into liquid and gives it a shot of high shear on the fly before it can agglomerate, fisheye or glump. The worker-friendly floor-loaded equipment also has important ergonomic advantages. Mounted on casters, it becomes a piece of equipment that can be wheeled almost anywhere in the plant -- answering the ongoing need for versatility and flexibility in plants everywhere.

High-shear mixing is the dominant trend, agrees Chris Ross, vice president of sales for Charles Ross and Son Co. (www.mixers.com), Hauppauge, N.Y. His company has introduced a patented technology, its X-series of MegaShear and ultra-high shear equipment for fine emulsions and dispersions.

High-shear mixing under vacuum will be changing the look of mixing in a plant, Berlan believes. The absence of bag opening and poured top entry translates into cleaner air and cleaner surfaces -- for a healthier and safer plant environment.

In-line blending

In-line blending methods provide processors with alternatives to tank mixing. Instead of the juice maker's typical blending of water, sweetener and juice in a tank, for example, in-line blending enables the processor to run water or other liquid while adding ingredients in a continuous stream.

"Modern plants are doing this more and more," says Tetra Pak's Berlan. "Before, they did it with just syrup and water. Now they are running five or six streams of product into the flow."

Allowing the processor to blend as needed, in-line blending is more efficient, he argues. "You don't have to blend in the tank and constantly check your concentration or mix of ingredients. You just blend in line and add ingredient as needed as product flows to the filler."

"We are seeing a lot more in-line mixing," says LeClair of APV/Invensys, noting that processors have been switching to his company's Darmix in-line mixer to get away from batch mixing. "Continuous mixing is a trend driving the industry today."

Increasingly complex ingredients make for increasingly complex challenges for mixing and blending, especially in trying to keep air out of the blend.

Indeed, a manufacturing executive at one of the word's largest soft drink makers has admitted that his company is considering switching much of its production to in-line systems. He calls them "more progressive" and foresees such systems becoming the norm.

Advantages of in-line blending include:

  • Less floor space - In-line blending is a streamlined function that takes up a smaller plant footprint.
  • Continuous operation - Batching becomes unnecessary in the continuous stream.
  • Improved accuracy - In-line blending is highly accurate and lends itself well to automated operation.

"Six Sigma methods of checking accuracy favor in-line blending," Berlan adds. "This is another way in which (new) blending methods are influencing plant design. Your operation becomes very streamlined."

Ribbons and more

More and more processors are turning to ribbon blenders for dry blending, spices and flour applications, says Chris Ross. The outer ribbon of a ribbon blender moves product in one direction while the inner ribbon moves it in the other. Ribbons also rotate to move product both laterally and radially.

"Anything that is dry blended can take a ribbon blender or a vertical cone-screw blender," says Ross, emphasizing the economics of these options.

Other "milestones" in mixing and blending technology, according to Ken Langhorn, technical director of Charles Ross and Son, include: powder-injection technology; agitator/stirrer designs; and high-viscosity blade designs on planetary mixers.

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