Ultrasound, chlorine combine to boost leafy green decontamination

12/10/2012 01:11:00 PM
Vicky Boyd

spinachUniversity of Illinois, Urbana, scientists have found that combining ultrasound treatments with a chlorine wash significantly reduces the number of E. coli 0157:H7 on spinach leaves.

Ultimately, the U.S. Department of Agriculture would like technology that achieves a 4- to 6-log reduction in pathogen cells, according to a news release.

A 6-log reduction is a million-fold reduction.

Technologies used by processors currently achieve about a 1-log, or 10-fold, reduction.

The University of Illinois technology yields a 4-log reduction.

Hao Feng, a food science and human nutrition professor, developed a pilot-scale system that used three pairs of large-area ultrasonic tranducer boxes to form a channel.

Spinach leaves in a continuous-flow chlorine wash flowed through the channel.

The key to the success, Feng says, is continuous flow and uniformity of the ultrasound field.

“Placement of the produce as it makes its way through the channel turns out to be very important," he said in the release. "We had to find ways to make sure that leaves received similar exposure to ultrasound, taking care to minimize the chance that one leaf would block a nearby leaf’s exposure to the sound waves.”

If even part of a leaf escaped ultrasound treatment, it could potentially contaminate the rest of the load.

Feng and his colleagues also tested the technology on iceberg and romaine lettuce with similar results.

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California  |  December, 13, 2012 at 11:54 AM

What becomes of the the residual chlorine wash? Is the product, spinach in this case, re-washed? Is this current technology such that leaf placement is not an issue as described above? Is there a QC/QA monitor in place on the wash line?

California  |  December, 13, 2012 at 12:17 PM

Those might be better answered by the study's leader, Hao Feng, at the University of Illinois. He can be reached at haofeng@illinois.edu.

Lyudmil Parvanov    
Bulgaria  |  December, 16, 2012 at 10:38 AM

To use chlorine on food - for more stupid "scientific achievement" I didn't heard about.

California  |  December, 17, 2012 at 09:21 AM

Chlorine, when used properly, is a useful tool to control disease-causing organisms. Nearly all municipal water supplies are chlorinated.

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