The wash-up on coronavirus and food from CSIRO


On our virtual sofa, we spoke with resident expert and senior food microbiology consultant, Cathy Moir. Here's what she had to say on all things food and coronavirus. Grab a cuppa and settle

On our virtual sofa, we spoke with resident expert and senior food microbiology consultant, Cathy Moir. Here's what she had to say on all things food and coronavirus. Grab a cuppa and settle in.

We research foodborne microorganisms. This ensures Australians continue to feel confident the foods we buy are safe to eat. We have a key role in food safety research globally. And we provide advice for Australian consumers and industry. At this time of the COVID-19 pandemic, we know messages can be confusing. So here is some advice about the risks of respiratory coronavirus and food in your home.

What is the risk of getting COVID-19 infection through food?

There is no current evidence you become infected by eating the coronavirus. It's a respiratory virus transmitted mainly via nose and eyes, not a gastrointestinal virus. The acid in our stomach is expected to inactivate the virus.

Should we be washing uncooked foods like fruit and vegetables more than usual?

It's not sensible nor practical to wash all the food you bring into your home especially at this point in time when we're not seeing widespread environmental contamination, nor extensive community transmission of the coronavirus in Australia.

My advice is from both a practical and food safety perspective. Washing fruit and vegetables in freshwater just prior to eating is enough. This aligns with advice from the US Food and Drug Administration. Please note - hand soap or dishwashing detergent are not designed for direct use on food.

However, at this time of heightened concern, the best advice is to wash your hands with soap - before and frequently - when preparing food and handling food packaging. Washing your hands and not touching your face will minimise the risk of getting an infection after touching surfaces or food packaging.

Remember, there is no evidence you get a respiratory coronavirus infection from eating it. Extra tips for cleaning fresh fruit and vegetables are available on the ABC.

Should we be eating uncooked food, like fruit, vegetables and salads?

Yes, please continue to eat fresh fruit, vegetables and salads. There is no evidence to suggest you become infected from eating coronavirus. The best advice is to wash your hands with soap when preparing fruit and vegetables and to rinse fresh produce with water just before you eat it.

What temperatures do viruses like to live in? Should we be refrigerating foods that we wouldn't normally?

Viruses don't 'live' or grow outside of their host, they merely exist until they are able to infect their next host. So there is no need to refrigerate food that you wouldn't normally.

What is the risk of getting coronavirus from surfaces?

The coronavirus that causes the COVID-19 infection is a respiratory virus. It is typically transmitted via respiratory droplets. These come from coughing, sneezing or close contact with other people. Infection may occur if the virus reaches our mucous membranes - eyes, nose and airways. Also after we have touched a contaminated surface and then our face. This is why good personal hygiene is the best way to avoid infection.

Three important things to remember:

  1. Wash your hands properly and frequently. Including washing your hands when you get home and before preparing food, which you should do anyway.
  2. Avoid touching your eyes, nose and mouth.
  3. Sneeze and cough into your elbow or a tissue and put used tissues straight in the bin.

Some additional hygiene advice is available on the Australian Government Department of Health website. Or read more about how the virus spreads.

How long does the virus survive on surfaces?

We don't know this yet for the virus responsible for COVID-19, but we're working to find out.

Coronaviruses can survive on surfaces for between hours and days. It depends on the type of surface, the temperature and humidity. Therefore we need people to focus on personal hygiene measures. Washing your hands properly and frequently and not touching your face is key.

What about cleaning at home? What sanitisers should we be using?

Again, we don't know this yet for virus responsible for COVID-19, but we're working to find out.

Cleaning should be done before sanitising as dirt can render some sanitisers less effective. Sanitising is different to cleaning - cleaning removes dirt, dust and some microbes. Sanitising is done to inactivate microorganisms.

Regular cleaning of surfaces at home is important. Cleaning with mild soap and water may be entirely adequate assuming there's no reason to think your home is highly contaminated. The coronavirus is an 'enveloped' virus which makes it fairly weak when it comes to cleaning. Soap breaks down the virus envelope, making it inactive.

The following sanitisers have been shown to be most effective at inactivating coronaviruses:

  • Ethanol 62-71 per cent for 30 seconds
  • 0.5 per cent hydrogen peroxide for one minute
  • 0.1 per cent sodium hypochlorite for one minute

Not all of these may be available or practical for use in the home environment. And importantly, more concentrated DOES NOT mean greater kill! Always follow the instructions for use on the container.

Hand sanitiser can be hard to buy at the moment. Is it true that you can use vodka?

You can use vodka but that seems a very expensive choice of sanitiser! Alcohol is most effective at inactivating coronaviruses (SARS and MERS) at concentrations of 62-71 per cent. So make sure you use a strong one.

I've over-purchased some items, what's the best thing to do?

If you find you have purchased too much perishable food such as meat and vegetables, find a good recipe, cook up your excess and freeze it for later.

With the boom in delivery and take away, how long can we keep takeaway food in the fridge?

Leaving food out on the bench allows more time for microorganisms to grow. Perishable food left out (in the temperature danger zone of 5-60°C) for more than two hours should be eaten or refrigerated immediately. If for more than four hours they must be thrown out.

Our top tips are:

  1. Put leftovers in the fridge straight away after the food has stopped steaming
  2. Divide large amounts into small containers so they cool quicker
  3. Eat within three to five days
  4. Reheat leftovers so they are hot all the way through, using a clean food thermometer to check the centre is 75°C

What is your advice on freezing/not freezing take away or leftovers?

Freezing is a good option for leftovers as it stops microorganisms from growing. Remember to date mark the container e.g. cooked/frozen on (date) so you know how old it is. When defrosting, move the food from the freezer to the fridge the morning or day before you need it. Or straight into the microwave or oven.

With Easter coming up, is chocolate still safe to eat?

Absolutely, eat chocolate! We need our comfort food. But not too much. Like everything, in moderation, but more than ever right now!

Original article written by Cathy Moir from the CSIRO

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