Dairy Processing Equipment Transitions from Tanks to Technology

Stainless steel tanks and kettles are synonymous with dairy manufacturing, but the long-term trend is toward continuous processes that don't require the tools of batch.

By Kevin T. Higgins, Managing Editor

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The Singh family calls it ice cream, but Kaurina's Kulfi is at best a distant cousin to the frozen, aerated treat most Americans recognize as an ice cream bar.

Introduced to the Indian subcontinent in the 16th Century, kulfi consists of corn starch, sugar, natural flavors such as mango pulp and pistachio, and milk that has been boiled down and caramelized. The other ingredients then are blended, and the compound is poured into molds and frozen, resulting in a novelty that is "basically a condensed version of ice cream with almost universal appeal," suggests Aman Singh, executive vice president of Dallas-based Kaurina's.

Kaurina's is a 13-year-old commercial enterprise that is slowly spreading to the East and West coasts and winning an audience outside the Indian ethnic niche. An electrical engineer, Singh carefully treads the line between automated production and his family's secret recipe for kulfi.

"No one knows how to cook the milk to the right consistency except the members of our family," he says. The process has evolved from stockpots that were stirred by hand to 80-gallon kettles with agitators. Evaporators that could more efficiently remove the water would be a step up; so would a pump to transfer the blend to brine tanks for freezing.

Until demand can justify automation, Singh must rationalize the process as a guarantee of quality, a hedge against bowdlerization. In that sense, he is like every other dairy processor that clings to batch processes. Continuous options are proliferating in dairy, aided and abetted by sanitary rotor stator assemblies that provide an option to stirred vessels and static mixers.

Adding dry ingredients to a fluid stream is becoming common. Some yogurt recipes used at Commonwealth Dairy in Brattleboro, Vt., require the introduction of powders before milk moves to fermentation tanks. In-tank mixing is the traditional approach, but the two-year-old dairy is not bound by tradition. Instead, Commonwealth uses a low-shear blending system powered by a 20hp motor and outfitted with a special impeller to mix powders in line. "It's very expensive," production manager Berthold Gruber says of the system, "but essentially it's nothing but a pump."

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Pump specialists beg to differ. Finite particles are a challenge for mechanical seals, and when ice cream processors mix chocolate, shearing can produce a glassy substrate that can bind and break a pump, according to Wallace Wittkoff, global director of the hygienic segment of Pump Solutions Group (PSG), Redlands, Calif.

If those fine particles are to be blended in line, there must be sufficient clearance between the rotor and stator to avoid binding and shear while minimizing pump slip. One solution is PSG's Mouvex, a positive displacement pump featuring "eccentric disk technology" that self-adjusts pump clearance with a spring-based automatic clutch. The result is low shear and minimal slip.

Progressive cavity pumps can deliver similar performance, Wittkoff concedes, but they require control loops for back pressure control and process stabilization. "It's difficult to do and very inflexible," he says, whereas the Mouvex unit only requires one control loop.

In-line mixing and formulation of dairy-based products "seemed like a no-brainer to do in the '90s" as a way to speed production and eliminate tanks, agitators and other elements of batch processing, recalls Wittkoff. But technical barriers quickly emerged. "Most pumps just don't have a tight enough control band," he notes, "so you can't settle down at the right ratio to produce consistent product."

An exception is Mouvex, manufactured in France and acquired by PSG a dozen years ago. The pump is widely used in Europe by Nestle and others to produce yogurt and other sensitive products. More recently, Nestle's Edy's plant in Fort Wayne, Ind., incorporated it into chocolate ice cream production.

Originally a Borden's facility, the 28-year-old Edy's plant has a throughput of 50 million cases a year, according to plant manager Sheila Brojeck. Almost 300 SKUs are produced, although mainstays like vanilla, chocolate and vanilla-chocolate blend are being filled daily. Continuous mixing is the rule, with a 750-gal. staging vessel for vanilla paired with two chocolate vessels with an equivalent amount of ice cream. A WCB pump undergoes monthly calibration to ensure that equal amounts are drawn from the complementary vats for 50-50 flow to a filler outputting 75-80 cartons a minute.

Newer mixing and blending technology from WCB-parent SPX includes the APV Cavitator, a system introduced at the 2011 Process Expo show. The system combines an APV centrifugal pump with a controlled cavitation chamber that is particularly adept at mixing and heating sensitive proteins such as whey protein concentrate and other dairy fractions.