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Food Safety Clear And Cold - April 2007

The forecast for food safety should be bright if you emphasize these postharvest principles.

By David Eddy
Senior Western Editor

THERE are an awful lot of factors involved in maintaining postharvest quality of your crops, but keeping two principles in mind will go a long way to ensuring your products are safe and of high quality. If you keep your produce as cool as possible, and keep your water as clean as possible, you will definitely be on the right track, says Trevor Suslow, a University of California Cooperative Extension postharvest specialist.


	Rules For The Road

	Here’s a list of ten pointers, from harvest to postharvest, to help you minimize food safety problems and maintain quality. Harvest the product at the correct stage of maturity during the coolest time of the day to maintain low product respiration. Minimize handling as much as possible. Avoid unnecessary wounding, bruising, crushing, or damage from workers, equipment, or harvest containers. Shade the harvested product in the field to keep it cool. By covering harvest bins or totes with a reflective pad, you greatly reduce heat gain from the sun, water loss, and premature senescence. If possible, move the harvested produce into a cold storage facility or postharvest cooling treatment as soon as possible. For some commodities, such as berries, tender greens, and leafy herbs, one hour in the sun is too long. Keep the packingline clean. Use clean potable water or a sanitizer if the water is reused. Maintain good, strict worker hygiene. Use cleaned and, as necessary, sanitized packing or transport containers. Do not compromise high-quality product by mingling it with damaged, decayed, or decay-prone product in a bulk or packed unit. Pack carefully. Sort, classify, and pack carefully in an adequate container to protect product. Ensure that boxes are well-placed on a strapped pallet. Train, provide tools, and pay special attention to workers involved in critical handling steps.

Temperature is predominately considered a factor as it affects quality. However, when it comes to food safety, keeping your produce cool - maintaining the "cold chain" - is also critical, especially for fresh-cut products, says Suslow. That’s because, quite simply, warmer temperatures help dangerous bacterial pathogens such as E. coli grow.

After the product has been harvested and cooled, it shouldn’t be allowed to climb above 50°F if at all possible, says Suslow. If something should go wrong, and the product begins to heat up, food safety really becomes problematic. For example, if the product gets up above 80°F during transport and distribution, E. coli and salmonella populations can double every hour. And at 90°F, the growth rate will begin doubling every 35 to 40 minutes. "That could mean going from 20 to 20,000 cells (of E. coli) on a fresh-cut product on a cross-country trip," he says, adding that it can also be an insidious problem. "The numbers can go up 100-fold or even 500-fold, and the product still looks fine."

Growers really need to keep a close eye on temperature in late summer. Not only is the ambient air temperature higher, but that’s when many crops are being harvested. "When you get into the late summer months, everyone’s competing for trucks," says Suslow. "Operators who don’t normally handle perishable foods start showing up."

Don’t Overload
Growers also need to pay a lot of attention to water quality, says Suslow, as even a short-term lapse in management can lead to critical problems. Many packers and shippers use chlorine because it’s generally effective and inexpensive, but the chlorine and pH levels need to be frequently monitored. "If you allow chlorine to drop below the necessary level and have too high a pH, microorganisms in the water aren’t killed fast enough and can move inside the harvest wounds, for example, and you can’t get them out," he says.

Besides letting the chlorine level get too low, another area of concern is that growers can try to push too much product through the system, exceeding capacity. When that occurs, the product doesn’t get enough "dip" time. "For example, a dip or spray of eight to 10 seconds may be all the product sees, but for many products, that’s insufficient," he says. "It would be just enough time for cross-contamination to occur, especially if the chlorine was too low."

To speed the process, many growers are going with systems that involve more mechanical action, such as jets or bubblers. Suslow says that those systems can help, though growers need to be cautious. "We know they’re not 100% effective, but they can remove some problems," he says. "What’s important is to pay attention to the entire system."


	Sober Realities

	University of California Cooperative Extension postharvest specialist Trevor Suslow recently testified at a hearing of the California Assembly and Senate Committees on Agriculture regarding last fall’s E. coli outbreak on spinach that killed four people. Suslow, who is also a columnist for American/Western Fruit Grower’s sister publication, American Vegetable Grower, said that the politicians were taken aback by how daunting the task is in ensuring a safe food supply. Here is a list of the "sober realities" Suslow presented: Available science and novel research cannot meet all immediate needs of consumer assurance and protection, resolve apparent environmental quality conflicts, nor fulfill all industry requests for data-based guidance in food safety practices. Much of the produce-based research has been fragmented and constrained or largely lacking in practical relevance. Lack of research is not always a justifiable rationale for recurring outbreaks. Technical communication on food safety does not always reach or is often not well received by smaller operations and diverse farm management philosophies. The division and factions emerging from the aftermath of the Fall 2006 outbreaks are not new but have brought in new stakeholder groups and thrust the issues into the public eye. Polarization among food safety and environmental practitioners over farming and the environment does not serve the public good. Conflicting messages from academia regarding state of the science and the path forward for solutions leave consumers with diminished confidence in safety and elevated concerns for unintended impacts on environment and small farm integrity. Current funding in basic and applied research and Extension outreach is inadequate and not optimally organized to best contribute to solutions.

E-mail questions or comments about this article to deddy@meistermedia.com.