Clear And Cold

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.

Temperature is predominately considered a factor as it affects quality, but 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 even handle perishable foods start showing up.�

Don’t Overload

Growers also need to pay a lot of attention to their 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 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 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.