Safer salad suggestions from University of Arizona researchers

Produce specialists are investigating the increase of contaminated fruits and vegetables and advising consumers on how to protect themselves.

It’s been a year since the last lettuce and spinach recall, nine months since a peanut butter recall, six months since olives were recalled, five months since a recall on Veggie Booty, a snack for kids made with spinach and kale, and three months since canned fresh cut green beans were recalled.

According to figures from the U.S. Food and Drug Administration, the number of outbreaks of food poisoning caused by microorganisms has risen in recent years.

In a paper published in American Scientist magazine’s November/December issue, University of Arizona (UA) produce specialists review the harvest-to-home process and offer advice to consumers and harvesters on how keep bacteria at bay.

Jorge Fonseca, UA assistant professor and vegetable post-harvest specialist, and Sadhana Ravishankar, an assistant research professor studying stress response in foodborne pathogenic bacteria and its control, say the increase in outbreaks of food poisoning is largely due to people eating more fresh fruits, vegetables, and salads and more meals outside of home.

Fresh fruit and vegetable eaters are at risk because the produce may have been grown in contaminated soil. Compounding the risk of contamination is the centralized process of preparing and distributing foods. The risk is high because large amounts of food are susceptible to widespread contamination if bacteria are present during the process and distribution stage, before it is sent to grocery store shelves.

Their study of the harvesting, processing, and packaging stage revealed that fruits and vegetables pass through more hands than ever before — hands that may pass on the bacteria. Adding to the problem of contamination is that now, more and more fruits and vegetables come from abroad, which adds days of transit time along with questionable standards of care and storage.

These issues give bacteria the opportunity they need to potentially cause illness and even death in hundreds of households across several states at any given time.

“This review research was important because publications concerning food safety often lack a holistic approach that converges the concern from the growers perspective with the consumer perspective. We try in this publication to fill that gap,” said Fonseca, who is a vegetable expert from the ground up. He works in the fields with growers in Yuma at the UA Yuma Agricultural Center and is an avid consumer of their products.

Two bacteria are usually responsible for contamination of packaged sprouts and leafy greens — Salmonella and Escherichia coli O157:H7 (E. coli). Among foodborne pathogens, Salmonella bacteria caused one in five outbreaks between 1990 and 2003 attacking tomatoes, melons, and sprouts.

The Salmonella bacteria is able to survive in fruits or vegetables that are acidic like tomatoes. It is an intestinal microbe that lives in the soil of incompletely composted manure from wild or domesticated animals. If produce that is grown in contaminated soil is not washed thoroughly, Salmonella that is still clinging to its surface can spread to the inside during slicing or cutting. They also found that it may enter the seeds of a plant before germination and grow within it.

As recently as fall 2006, a multi-state outbreak of E. coli, a deadly strain of bacterium that is normally found in all human intestines, was linked to bagged spinach; it killed three people and sickened more than 200.

Fonseca and Ravishankar believe that the rise in E. coli tainted fruits and vegetables comes partly from fields that used to contain animals where their feces, feces-laced irrigation water, or raw manure used as a soil additive offer bacteria a place to live and offer an easy jump onto the harvest.

Alarmingly, bacteria can survive for months after the animals are gone, depending on weather conditions and soil properties.

Adding to the contamination risk, the researchers found, is irrigation from overhead sprinkler systems or circumstances in which a crop is harvested immediately after irrigation or rainfall. The overhead watering can cause splashing, which carries soil contaminants to the harvest’s leaves.

So are organics the safer bet? Not necessarily. The researchers review found that non-certified organic products had higher levels of bacteria than conventional products.

The researchers warn against organic crops unless the package is labeled as certified organic produce. New federal regulations for certified organic produce state that growers must obtain a certificate that proves the products they use for crop production are free of harmful bacteria.

After harvest, contamination may include bacteria transmitted by people whose hands or tools are dirty with human or animal feces or their own infections. Adding to the risk is the resilience of the bacteria, which thrive in the high-moisture and-high nutrient content environment that vegetables and some fruits provide.

Produce with irregular or wounded surfaces are ideal for the entry of E. coli but even the unblemished or smooth surfaces on food-processing equipment can house microcolonies.

Recommendations for harvesters and produce distributors:

-Wash hands and surfaces where food is prepared for distribution. Sanitizers at the point of harvest are recommended but the authors stress the importance of hygiene of workers to reduce risk of contamination;

-Use sanitizers. The spectrum of post-harvest treatments includes chemical, physical, and nuclear processes. Of these, household bleach is the cheapest and most commonly used; and

-Handle the produce gently. Fonseca and Ravishankar say that regardless of the potency of the sanitizer used, harvesters and packaging plants whose operations handle fresh produce gently will probably yield safer fruits and vegetables than operations in which nicks and bruises are common.

Recommendations for consumers:

-Wash kitchen surfaces and tools before and after preparing foods;

-Wash hands thoroughly before cleaning the produce;

-Use lukewarm tap water and a clean cloth or scrub brush to wash the produce vigorously. Washing fruits and vegetables before eating them causes the bacterial contamination to be reduced tenfold;

-Trim bruises, damaged areas, and the produce’s stem and the area around the stem;

-Do not place or prepare produce alongside or on the same surfaces as raw meat or eggs;

-Save washed produce only after you dry it in a salad spinner or with a towel; otherwise, throw it away; and

-Keep produce that can tolerate low temperatures in the refrigerator and throw away produce that looks or smells bad.

“Overall, it’s important to put the risk of eating produce in a larger context. Eating fresh fruits and vegetables is certainly no riskier than most of the other daily activities. Depriving ourselves from consuming fresh fruit and vegetables may be riskier in the long term, since it has become clear from a number of studies that nutrient quantity and quality of fresh fruit and vegetables are keys to prevent health problems,” Fonseca added.

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