By: Heather Williams

The Salmonella infected papaya situation does not seem to be resolving anytime soon. Salmonella is a bacteria normally found in the intestinal tract of reptiles, birds, and mammals but when it makes its way into fruits and vegetables, it can cause major issues for human health.  The current outbreak that spans 21 states has sickened 173 people and killed one is not the first time these papayas have been in the news.

In 2011, papayas originating from the Agromod papaya plantation were affected.  According to investigations, the plantation had an interconnected drainage ditch system for irrigation.  These “marsh-like” drainage ditches are an ideal habitat for frogs, waterfowl, and other wildlife.  It also provided the perfect environment for pathogenic bacteria.  After a heavy rain and flooding, the ditches can overflow into the soil surrounding the crops, pushing the pathogens into the papaya tree along with the water.  This is where the pathogens are introduced.  Investigation are still underway in the current Maradol papayas originating from the farm Carica de Campeche.

How Does Salmonella Get Inside the Fruit?

While it may be impossible to eradicate Salmonella completely from the farm environment, luckily studies how shown that pathogens cannot enter the fruit through the root system and contamination is limited to the external areas of the fruits.

In 2006, a produce company called Fresh Express funded research on E. coli and spinach to determine if pathogens can move from the soil into the stems and leaves of the vegetable.  Their research identified that while the E. coli made its way into the roots, the internal structures of the plants were pathogen free.  This brought researchers to the conclusion that the E. coli contamination originated from the external parts of the plants.

Researchers at the University of California, Davis conducted an investigation on Salmonella contamination in cantaloupes.  Their research indicated that Salmonella could not move from contaminated soil beyond root structures, indicating that external contact with pathogens was the primary method of contamination.  They suggested that irrigation water or ground surface contaminations could transfer pathogens to the melons during normal growing and transportation activities.

Unless the fruit has a cut, nick, or bruise, the pathogen cannot make its way inside the fruit.  Care must be taken after the fruit makes it to your home to thoroughly wash it to remove potential pathogens before eating it.  However, better sanitation and preventative controls during the harvesting, packing, and distribution of produce could reduce the bacterial load of the harmful pathogen, helping to reduce consumer exposure.

How Can Contamination Be Limited at Each Step of the Process

While all contamination cannot be removed from existing soil, there are activities that could be included in the growing and processing steps that can reduce exposure.  Consider each step of the process from initial seed propagation all the way to shipment.

Seed Propagation

Seed propagation occurs often in a greenhouse or other controlled environment.  During the sprouting phase, sprouts are susceptible to pathogen infection.  The warm, moist environment provides a perfect breeding ground for pathogenic bacteria, introducing the fruit to contamination at this very early stage.  To limit contamination, using properly composted materials to grow seedling is required.

Seedlings are Transplanted and Grown to Maturity

Once seedlings reach a sufficient size they are transplanted to the field where it spends the next six to nine months maturing.  During this and the next two to three years of its expected lifespan it is exposed to a variety of plant risks.  From pests to root rot and powdery mildew to papaya ringspot virus, the papaya battles many factors.  Other factors becoming more well-known include pathogens like Salmonella that do not affect the plant directly, but provide an environment for it to grow until it is transported to the consumer.  To reduce contamination at this stage, clean irrigation water is very important.  There is no way to completely get rid of the pathogens in the existing environment, but reducing new pathogens from being introduced to the croplands is achievable.  Any fertilizer used should be properly composted to be sure live pathogens are not being transferred. 

Harvesting

Once the fruit on the papaya trees have matured, it is time to harvest.  Sanitation of workers such as access to proper bathrooms and handwashing sinks reduces contamination risk from fecal-oral transmitted pathogens.  Care to avoid contaminating one area of cropland with the other should be exercised, in case some areas are cleaner than others.

Sorting

Once the papayas have been harvested they are delivered to the packing house.  Here, each papaya is graded according to ripeness and size.  They are then sorted again for size, shape and color.  Here the fruit is examined for damage.  This is a step where fruit with nicks, cuts, and bruises should be excluded.  Fruits with damage allow surface bacteria to breach the protective skin and can contaminate the interior of the fruit.  Additionally, sanitation and hygiene of those handing the fruit is important to reduce introduction of additional bacteria and spread of bacteria from one batch to another.

Treatment

Once sorted, the papaya are washed, generally in large vats of chlorinated tap water.  This removes dirt, debris, and insect contamination.  If an appropriate solution is made, it could also kill pathogenic bacteria.  The fruit is inspected again and depending on the condition or expected final destination, may undergo additional treatments such as a hot water bath or fungicidal dip.  The fruit is then air-dried and packaged for shipment.  Worker sanitation and hygiene is also important at this critical step.  Maintaining clean hands when working with the fruit will reduce the introduction of fecal-oral pathogens and help prevent the spread of bacteria that may be lurking from one batch to another.

Shipment

The product is then shipped out to distribution centers through a variety of means depending on the end destination.  From this point, the farm and processing house has done all that they can do to reduce the propagation and spread of pathogenic bacteria.  If there is any residual bacteria present on the fruit, the consumer should be removing it with proper handling and washing practices to keep themselves and their families safe.  This can be achieved if the fruit is not grossly contaminated.

Additional Studies

It would be interesting to see if any studies come out of this outbreak.  With Salmonella being linked to papayas several times, it seems that more research could be done to identify exactly what steps lead to the most contamination risk and promote methods that would reduce pathogen growth and transfer.

UnsafeFoods.com will be monitoring the situation and update when more information is available.

http://www.unsafefoods.com/2017/08/06/papaya-outbreak-grows-109-infected-people-salmonella-get-inside-produce/