July 25, 2007

Ozonator: Blasts bugs in grain bins

An ozonator takes oxygen from the atmosphere and adds an electric charge to make ozone, which is then pumped into a grain bin by a generator, said Linda Mason, a Purdue Extension food pest entomologist. The grain bin has a fan at the bottom that pulls the ozone through. The remaining ozone is then recycled through a tube back to the top and used again.

"Many are familiar with ozone, they just aren't aware of it," Mason said.

For example, the smell after a lightning storm is ozone, and the smell from a welder's arc also is ozone. Ozonators also are placed in public restrooms to remove odors.

"The great thing about ozone is that it does not leave a pesticide residue on the product and it doesn't affect food quality," Mason said.

The ozone goes in at a very high concentration, and the first time ozone is put into a bin, it attacks and breaks all the double bonds on the grain kernels and all the dust and debris in the bin, Mason said. It also will do the same to insects. Now the grain is considered to be in Phase II.

When ozone is put into the grain bin in Phase II, instead of having to break double bonds as it goes through, it' will kill any bug that has entered the bin.

Mason and the Purdue Post-Harvest Grain Quality Program experimented with corn, popcorn, rice, malting barley and wheat. These grains were ozonated and then processed for food. The team was concerned that the process might cause some food quality issues, such as the food losing its flavor and adhesiveness, because of the attacking of double bonds. Fortunately, the food quality is not affected by the process, Mason said.

"The other advantage is that ozone will attack fungal pathogens like Aspergillus flavus, a mold that affects corn and produces an aflatoxin within the grain bin," Mason said. "When we treat with ozone, we reduce conidiation or essentially eliminate mold spores from the grain and considerably reduce the aflatoxin concentrations in there, too.

"However, that doesn't mean that if you were to re-wet the grain that you're not going to get a mold problem. New spores are always entering the bin and ready for conditions to accelerate growth. Because there is no residual, there is always potential for reinfestation with insects and mold."

Ozonation is only effective while it's ozonating, Mason said. Once the bin is opened, a bug can safely enter because there is no ozone left in the bin. Mason recommends ozonating every six to eight weeks to reduce the number of insects and molds that may have gotten into the bin since the last ozonation.

This technology is used widely in the potato industry for storing potatoes. Mason predicts the organic industry will be the next to adopt the process.

"They have no alternatives to use right now," she said. "They are really struggling to find ways to control insects in bins, and ozone is already approved for the organic market."

From the organic market, Mason predicts the process will then find use in the high-value grain and specialty crop industries.

Writer: Julie Douglas, (765) 496-1050, douglajk@purdue.edu

Source: Linda Mason, (765) 494-4586, lmason@purdue.edu

Ag Communications: (765) 494-2722;
Beth Forbes, forbes@purdue.edu
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