Against the grain

New drying technology reduces rice's moisture content from 18 percent to 12.7 percent in as little as two hours

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Companies that process grains, herbs or peanuts, as well as colorants, flavorings and other dry ingredients, must substantially reduce product moisture in order to preserve product integrity. 

 

The challenge is to do so quickly, without generating regulated emissions. Given the fragility of materials such as grains, care must also be taken to avoid temperatures or material-handling methods that can result in stress cracking or breakage.

 

Although infrared energy has long held the potential to satisfy these requirements, until recently it was unable to achieve the low temperatures, high throughput and product damage prevention required for commercial applications. With support from the U.S. Department of Energy (DOE), however, Catalytic Drying Technologies (CDT) of Independence, Kan., has developed a hybrid infrared technology that shows promise in meeting these objectives. In fact, tests conducted over a 42-month period indicate the technology can reduce moisture content from as high as 60 percent to as low as 3.4 percent.

 

Rather than targeting the entire product, as convection heating typically does, infrared energy only targets moisture within the product, explains Virgil Macaluso, president of CDT. "Infrared energy, which is emitted in wavelengths, has a peak emission spectrum of 3 to 7 microns, while water has peak absorption of 3, 4.5 and 6 microns," he elaborates. "So the emission spectrum nicely overlays the absorption spectrum of water."

 

Rice from the field, he continues, typically has a moisture content of 18 and 22 percent, though a range of 12 to13 percent is typically required for storage. The CDT dryer dries rice with moisture levels of 18 percent to levels of 12.7 percent in two hours, as compared to the three to five days required by more conventional, multi-stage methods currently in use, Macaluso says. Tests show the CDT dryer consistently achieves a three-hour cycle time at temperatures below 110 degrees F and produces high milling yields. Macaluso says it is suitable for both rough ("paddy") and parboiled rice.

 

Likewise, tests have shown that catalytic infrared technology is well suited for extracting high-potency vitamin content from herbs used in dietary supplements, infant formula, functional foods and livestock feed.

 

In the case of Rosemary, for example, some form of commercial dehydration is required to extract Vitamin E from the herb, which at harvest has a moisture content of 60 to 70 percent. The goal is a moisture level of 8 percent. Dehydration by convection , the most

common method , meets the requirement in a 24-hour cycle, while the Catalytic system achieves meets it in three hours, and has the additional benefit of enhancing the yield's potency.

 

Insect control too

 

Although insects damage millions of tons of stored grains every year, options for controlling that type of damage are often expensive, highly regulated and ineffective. One of the more widely used treatments -- methyl bromide -- is currently being phased out in the U.S., while replacements such as phostoxin or CO2 heat systems are generally more expensive, less effective and have negative "environmentals." Organic food producers can't use these at all, and their alternatives are even more problematic. 

 

The CDT catalytic infrared system kills grain insects, eggs and larvae faster than pesticides, and more effectively than conventional heating, according to Macaluso. "Much as it does with food material, the system targets the water within the insects," he says." Tests show 100 percent kill rates when insects are exposed to infrared energy for as little as 10 seconds at 60degrees C.

 

The infrared heaters used in this system are flameless, and approved for use in Class I, Division 2, Group D hazardous areas by Factory Mutual Research and the Canadian Gas Association.  They chemically convert natural gas or propane to infrared energy, with carbon dioxide and water as by-products.

 

 

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