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


China could be using Taiwan as a testing ground for disinformation campaigns
102550 2019-02-20 00:00:00Z World

China could be using Taiwan as a testing ground fo…

by Gavin Ellis

A Taiwanese diplomat’s death in Japan has become a symbol of the consequences and dangers of disinformation.

Read more
The best way to beat food cravings? Fill up on the objects of your desire
102087 2019-02-20 00:00:00Z Nutrition

The best way to beat food cravings? Fill up on the…

by Jennifer Bowden

Research has shown that dieters’ attempts to resist eating certain foods appear to lead to cravings for those foods.

Read more
Deepfake: How disinformation fools our brains and damages democracy
102545 2019-02-20 00:00:00Z Tech

Deepfake: How disinformation fools our brains and…

by Gavin Ellis

Message manipulation using bots, algorithms and, now, AI software is making it harder to know what’s real – and threatening democracy itself.

Read more
Move to introduce digital tax for foreign companies profiting online
102519 2019-02-19 09:23:12Z Economy

Move to introduce digital tax for foreign companie…

by RNZ

New Zealand is lining up to introduce a new tax on multinational companies that make money out of online goods and services in this country.

Read more
National's high-risk gamble on marijuana and euthanasia
102484 2019-02-19 00:00:00Z Politics

National's high-risk gamble on marijuana and eutha…

by Graham Adams

Having polarising MPs like Paula Bennett and Maggie Barry leading the opposition to popular reforms could be kryptonite to the National Party.

Read more
Reflections on my encounter with the charming Dan Mallory
102482 2019-02-19 00:00:00Z Profiles

Reflections on my encounter with the charming Dan…

by Michele Hewitson

He penned a bestselling thriller, but as Michele Hewitson discovered, author Dan Mallory also proved himself to be a charmingly adept bullshit artist.

Read more
Sounds of summer: Notable Kiwis name their favourite summer songs
102500 2019-02-19 00:00:00Z Music

Sounds of summer: Notable Kiwis name their favouri…

by Phil Gifford

How music can transport you back to your most memorable summer.

Read more
Inside the close-knit community that lives along the Cromwell-Tarras Rd
102505 2019-02-19 00:00:00Z Travel

Inside the close-knit community that lives along t…

by Mike White

Mike White heads up the Cromwell-Tarras road to merino and wine country.

Read more