By Annalisa Hultberg, Extension
Educator, Food Safety
Harvest is well under way, and crops
are coming in strong in many areas with our intense heat. As you prepare your
products for sale, many are rinsed to remove soil or cooled in water to crisp
them up. While rinsing produce can cool it and remove that soil, it also can
spread contamination that might be present on the exterior to other produce,
making a small problem a bigger one.
For example if a melon or lettuce
leaf had fecal contamination from a bird or rabbit, and that produce was put
into a bulk washing tank, the pathogens in the feces can spread to the other pieces via the water.
Contamination can also be introduced from workers hands or from dirty wash
tanks or tools. Illness from the bacteria can include diarrhea, vomiting,
fever, nausea, and can even be more serious for some individuals with
compromised immune systems.
Some basic steps can go a long
way to reduce the potential risks of contamination in your postharvest washing,
and also have the added benefit of improving shelf life and storage quality of
your product. Here are some tips to think about as you rinse your fresh
produce to ready it for sale.
1. All water used for washing,
cooling and other postharvest use must be like drinking water.
First, consider the quality of the
water you are using to wash your produce. Well (ground) water should be
tested at least annually for bacteria. Municipal water does not need to be
tested. Surface water like streams and ponds should never be used for
postharvest applications like washing produce, since the water quality is
highly variable and this water is vulnerable to bacteria and pollutants from
animals, runoff, flooding and other sources of contamination.
Test well
water at least annually for presence of generic E. coli. Results
should indicate not detectable in 100 ml. When you call the lab, they
might say that a potability or drinking water test is generally for total
coliforms. Coliforms are an indicator of the water quality and of
bacterial contamination in the well, but E.coli is better as
it is a direct indicator of fecal contamination, and therefore the likelihood
that there will be harmful pathogens in the water. The FSMA Produce Safety Rule
requires testing for the presence of generic E. coli. Tests
are about $35- $40 each.
To find a lab: Minnesota Department of Health Accredited Labs database or
for more information about water testing and to find a lab, see Testing Water for FSMA Produce Safety Rule.
Taking a
water sample from a well head
2. Don't wash unless needed
Not all produce should be washed
before it goes to the customer. Herbs and berries are typically not washed
until right before consumption, as washing begins the process of degradation
and will result in lower quality produce with a shorter shelf life. Of course
many crops do need to be washed to remove field soil and/or to hydrocool and
crisp up. However sometimes washing can actually increase the risk of
contamination, as water spread pathogens readily, moving fecal contamination
around via the water. So, washing should be done with care and only when
needed.
Consider the crop before washing. Do
the peppers, cabbage, tomatoes or eggplant need to be washed? Depending on the
crop, how it was grown (on plastic much for example, or in a high tunnel), on
the rainfall, perhaps no postharvest cleaning is needed at all. Sometimes they
are simply dusty and a light rub with a clean towel or paper towel is all that
is needed.