PURE Bioscience Inc. of El Cajon, CA, has already seen excellent results with its patented antimicrobial agent silver dihydrogen citrate for use in direct contact cleaning in restaurants and food processing facilities. On Oct. 9 the company filed a food contact notification with the U.S. Food & Drug Administration to use SDC as a prewash on fresh produce that could eliminate bacteria a hundredfold above current methodology.

The company's research has already shown promise in poultry processing and a food contact notification for that use filed with FDA earlier this year is midway through the approval process.PURE Bioscience's patented silver dihydrogen citrate is already approved as a surface disinfectant and is under FDA review for use as a produce prewash. (Photo courtesy of PURE)

SDC shows particular promise for leafy greens and other problematic produce items, Chief Executive Officer Hank R. Lambert told The Produce News.

"We've been able to demonstrate in extensive testing that SDC displays superior efficacy versus sanitizers and disinfectants currently being used in the market," he said. "It also has the advantage of being non-toxic whereas most of the chemicals that are being used to disinfect food contact surfaces today are ammonia or chlorine based, they're irritants, they have warning labels. SDC is nontoxic, odorless, colorless and tasteless."

Testing performed at Kansas State University under the direction of James Marsden evaluated the efficacy of SDC against Salmonella, Listeria and E. coli O157:H7 on iceberg lettuce, spinach and cilantro. These leafy greens were chosen for evaluation because they are challenging to effectively treat during processing.

Hank LambertSDC achieved average reductions up to 2.36 log10 CFU/cm2 when applied alone as a spray and up to 3.10 log10 CFU/cm2 when combined with chlorine wash, simulating current processing steps. Sensory evaluations of produce treated with SDC indicated no difference in color, appearance or odor to untreated controls and SDC had no effect on the nutritional composition of the produce.

"We do feel like based on the very compelling test results that were generated [that] we've got a solution, a processing aid for produce that is superior to what's currently being used in the industry," Lambert said.

The Centers for Disease Control and Prevention estimates that produce was responsible for 46 percent of foodborne illnesses and 23 percent of foodborne illness-related deaths in the United States between 1998 and 2008. Leafy greens were identified as the primary source of foodborne illnesses.

"Produce processors and the Produce Marketing Association and all the trade groups are very focused on foods safety and take it extremely seriously and recognize the challenges they have, particularly with leafy greens," Lambert said. "We certainly hope and expect and have had preliminary conversations that indicate [the industry] would welcome a step forward like this."

Early indicators from the FDA are positive, Lambert said.

"They did come back with one set of clarifying questions about some references but did not question the efficacy or the residues -- that we took as a very positive sign," he said. "We had pre-meetings with USDA and FDA in Washington in May and they were both very optimistic about the potential in the processing of poultry. So we kind of smoothed the way for [the produce food contact notification] at that point."

The approval process takes about 120 days, and "We're very optimistic about obtaining FDA approval for the use in produce processing, certainly based on the test results and superior efficacy versus existing methods. All the evidence is very positive," Lambert said.