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Better blending, better biscuits; controlled doses of liquid CO2 provide free-flow flour and uniform dry ingredients blending.

It's snowing in Tulsa--inline, snow-like sprays of liquid carbon dioxide, that is. The cryogenic [CO.sub.2] is used in two temperature control systems by Bama Foods to condition flour during pneumatic conveying, and to keep dry ingredients cool during blending.

These two cryogenic applications, in use at Bama's biscuit facility, are only two examples of the company's well-documented quality improvement story (FP, Feb 1992). In under two years, the company has built a new plant and automated virtually every aspect of the business, from management philosophy to process control. Cryogenic-assisted dry materials handling is a small but significant part of the reason why Bama has retained the McDonald's buttermilk biscuit account for all restaurants East of the Mississippi River.

Flour conditioning

One of the temperature control systems is for pneumatic transfer of flour. The problem, at its worst in summer, is that when temperature and humidity rise, flour being pneumatically conveyed from storage silos is prone to clumping. This can clog conveying pipes and cause unscheduled downtime, or can cause inconsistent mixing, resulting in product reworks.

Bama solved the problem with a flour chilling system that uses two RTDs to transmit temperature readings to a control box. Inside are dual two-stage temperature controllers and relays for the exhaust blower and solenoid valves. When temperatures rise above a preset value, the solenoid valves open to release sprays of liquid [CO.sub.2] into the flour transfer piping via inline injectors. The [CO.sub.2] "snow" quickly chills the flour and dissipates, leaving no residue. Temperatures are automatically monitored before and after flour chilling.

Duane Cook, Director of Engineering, told FP, "This past summer, we customized the conveying controls and injectors to cool the flour before it even enters the plant." This, plus a collector that exhausts outside the plant, minimizes dust.

Bottom injection system

Just as in pneumatic flour transfer, too much heat in the dry ingredients blender can cause clumping and even elevated dough temperature.

When this happens, according to Cook, "Dough quality will vary dramatically. And if we vary the temperature of the dough, it greatly reduces our quality and consistency." Also, warm dough can stick to conveyors and cause downtime-inducing line jams.

A [CO.sub.2] injection system similar to the flour transfer installation ensures uniformity of the dry blending process. Using RTDs, controls, and solenoid valves, the system injects [CO.sub.2] into the bottom of the mixer. This "bottom injection" system effectively sheds the excess heat generated during blending.

Not only is it "snowing" in Tulsa, but flour runs free, ingredients keep cool, and the dough doesn't stick. Through daily and seasonal variations, consistent quality is key the success of Bama's buttermilk biscuits.

CardoxTM [CO.sub.2] Bottom Injection System and Pneumatic Transfer Temperature Control system, Liquid Air Corp., 5230 S. East Ave., Countryside, IL 60525.

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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Spotlight: Refrigeration and Freezing; cryogenic materials handling system, Bama Pie Ltd.
Author:Sperber, Bob
Publication:Food Processing
Date:Dec 1, 1992
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