Produce people, write this down: If you intend to keep the likes of Ralph Nader and Meryl Streep off your case, do what you can for food safety all the way from farm to fork.
Actually, everyone, from suppliers and handlers on to consumers, needs to do his part.
Sanitation at the farm level may not be as difficult as some imagine, provided contamination pitfalls are avoided, according to Trevor Suslow, Extension research specialist with the Department of Vegetable Crops, University of California, Davis.
Suslow has been investigating the survival of Salmonella, Cyclospora, E. coli, and other food borne pathogens in materials sprayed on grapes.
Speaking on at the recent San Joaquin Valley Table Grape Seminar at Visalia, he said food safety not only cuts across crop lines but is closely linked to food quality.
When it comes to the pathogens, there's nothing unique about table grapes. “They share the same sorts of concerns with many commodities, and that includes risks of perception.
“Wherever you have concentrations of animal production facilities adjacent to fresh fruits and vegetables typically consumed in raw form, there is potential for movement of pathogens by run-off, storm-related contamination, drift, dust, flies, or human movement.”
Critical for table grapes and other crops is the quality of surface water used for any applications, particularly foliar sprays. As these applications are made closer to harvesttime, the potential for pathogen carryover is enlarged.
One scenario is contaminated water finding its way into spray solutions. Well-water is fine, but if you transfer the water into a reservoir and us it later for spraying, you can be asking for trouble.
In his laboratory trials with contaminated water, Suslow said a non-pathogenic form of E. coli is persistent. The research focused on whether pathogens can survive in solutions of widely used fungicides and growth regulators.
“They don't necessarily grow, but the certainly aren't killed. If you start with contaminated water, there's potential for that to carry forward and be applied to the crop.”
Salmonella exposed to a pH of about 8.5 in a tank-mix of a common fungicide show “a tremendous genetic capacity to adapt to their environment. They will adapt to a very alkaline environment or a very acid environment.”
What happens to Salmonella on grapes in cold storage? Over a wide range of refrigerated temperatures, where the skin of the berry is intact, most of them die off. If they enter a break, or wound, in the surface, they tend not to multiply but to survive for an extended period.
When an SO2 pad is present, bacteria on refrigerated, intact berries died off, at least to detectable levels. There was little effect seen, however, on “wounded” berries.
Even though pathogens survived under laboratory conditions, Suslow wants to know how they survive under typical conditions in the field. Part of his intended research is evaluating organic foliar sprays that might carry nutrients that cause the Salmonella or E. coli to multiply.
He's curious too about the acid-adapted Salmonella, some of which can multiply well in a pH of 3.5. He also plans to investigate practices for washing produce that might be helpful to food service users and consumers.
Produce has taken costly black eyes from consumer watch dogs and the popular media over food safety, even though some cases proved to be nothing more than cross-contamination with tainted meat handled at the same location.
“However,” Suslow advises, “regardless of the economic impact of false associations, there remain real cases of produce-based contamination, illness, and even death attributable to the consumption of uncooked fruits, vegetables, and other perishable, edible horticultural commodities.”
In response, the produce industry encouraged voluntary food safety programs. The process of identifying and addressing potential sources of contamination and risk, he says, needs to be taken up by producers, buyers, and consumers.