What are the rules around eating unwashed fruit and vege?

by Jennifer Bowden / 14 May, 2017

Photo/Getty Images

Pathogens and agricultural chemicals in fresh produce pose a risk that should be taken seriously.

Question: Everywhere I went over summer, people were serving unwashed raspberries and strawberries. What are the rules here? Can you get sick from them?

Answer: Unwashed fruit and vegetables can harbour harmful bacteria and viruses that can certainly make us sick. Indeed, in March, Gisborne-based produce supplier LeaderBrand recalled some salad products because of the possibility that they had been contaminated with harmful Listeria.

Contamination of produce can occur at any point, from before harvesting in the field to serving at the table, with pathogenic (disease-causing) bacteria such as Salmonella and Campylobacter to viruses such as hepatitis A and the noroviruses, and parasites such as Cryptosporidium and Giardia. These foodborne pathogens aren’t common in fresh produce, but they have all caused outbreaks at different times around the world, says microbiologist Graham Fletcher, the research team leader for food safety and preservation at Plant & Food Research.

Washing helps to remove pesticides and chemical residues on fresh produce, he says, and typically reduces the quantity of pathogens. “It does make some difference and any difference is good, but it won’t remove all contaminants.”

The more thorough the washing the better, says Fletcher, but that depends on the produce and how much washing it can withstand: scrubbing hard-skinned vegetables such as cucumbers or potatoes under running water is a good idea. “The bacteria actually stick quite hard to cucumbers.”

Obviously, berries can’t withstand vigorous scrubbing. Fruits and vegetables with convoluted surfaces, such as raspberries or broccoli, should be soaked in water, with a little agitation to loosen any matter stuck to them, and then rinsed under clean water to wash away any contaminants.

As for Listeria on salad leaves, no amount of washing can completely remove the serious health risk for people with compromised immune systems – pregnant women and their unborn babies, the very elderly and those undergoing chemotherapy. In 2015, just 26 notified cases of listeriosis were reported, but four people died, three of them unborn babies. By contrast, campylobacteriosis is very common: there were 6218 notified cases in 2015, but no deaths. Hence the recent recall of all salad products potentially contaminated with Listeria.

Most human pathogens are transferred by infected hands touching produce or prepared meals, but Listeria is an environmental organism, says Fletcher. “It’s naturally present in the soil, in decaying leaf matter and in a lot of environments.” So it’s difficult for the food industry to keep Listeria out of the supply chain, especially in warm and moist food-processing environments

“A number of industries, particularly those dealing with meat, seafood and dairy products, where there is a lot of protein around, put a lot of effort into preventing Listeria growing in their environment.”

Cooking food at high temperatures can destroy most harmful foodborne pathogens. The Ministry for Primary Industries recommends boiling frozen imported berries, after an outbreak of hepatitis A in New Zealand was linked to them (bring frozen berries to the boil at 85°C for at least a minute). Foodborne illness outbreaks have also been linked to frozen berries in Sweden, Australia, the US and Ireland. However, this isn’t an option with fresh salads or other produce intended to be consumed raw.

Ultimately, fresh produce is grown in soil, which naturally contains bacteria, and there’s a good chance agricultural chemicals have been used on it too.

Aside from peeling and cooking, washing is our best line of defence as consumers, Fletcher says. “The more protection you have the better.”

This article was first published in the April 29, 2017 issue of the New Zealand Listener.


Get the Listener delivered to your inbox

Subscribe now

@nzlistener @nzlistenermag @nzlistener

Latest

The best thing to come from the Black Caps' defeat
108621 2019-07-20 00:00:00Z Sport

The best thing to come from the Black Caps' defeat…

by Paul Thomas

For New Zealanders, the Cricket World Cup final was a brutal reminder of sport’s great paradox. But there's hope on the horizon.

Read more
What New Zealand can do about the militarisation of space
108498 2019-07-20 00:00:00Z Tech

What New Zealand can do about the militarisation o…

by Duncan Steel

We may decry the notion, but the hostile use of space is creeping into the plans of various countries.

Read more
Five technologies from the space race that we take for granted
108506 2019-07-20 00:00:00Z Tech

Five technologies from the space race that we take…

by Peter Griffin

If US$154 billion to land 12 men on the Moon seems excessive, consider the things we use every day that had their roots in a Nasa lab.

Read more
Top investigator urges police to speak up about wrongful convictions
108539 2019-07-19 00:00:00Z Crime

Top investigator urges police to speak up about wr…

by Mike White

Mike White talks to investigator Tim McKinnel, who says police often turn a blind eye to possible corruption out of a misplaced sense of loyalty.

Read more
Jacinda Ardern to focus on Australia deportations in talks with Scott Morrison
108570 2019-07-19 00:00:00Z Politics

Jacinda Ardern to focus on Australia deportations…

by Craig McCulloch

PM Jacinda Ardern has doubled down on her criticism of Australia's deportation policy as "corrosive", ahead of her meeting with Scott Morrison.

Read more
How closed adoption robbed Māori children of their identity
108572 2019-07-19 00:00:00Z Social issues

How closed adoption robbed Māori children of their…

by Te Aniwa Hurihanganui

Te Aniwa Hurihanganui looks at the outdated Adoption Act and its impact on Māori who grew up desperate to reconnect.

Read more
The new robotic surgery aiding vaginal mesh removal
108377 2019-07-19 00:00:00Z Health

The new robotic surgery aiding vaginal mesh remova…

by Ruth Nichol

Women with complications caused by deeply embedded vaginal mesh are being helped by a pioneering surgical technique.

Read more
A beautiful mind: What people with Alzheimer's can teach us
108544 2019-07-19 00:00:00Z Health

A beautiful mind: What people with Alzheimer's can…

by Fergus Riley

North Auckland farmer Fergus Riley has uncovered many important lessons in caring for his father Peter, who has Alzheimer’s.

Read more