Some concern has been raised in nurseries and schools, particularly in Early Years and Primary, about a recent press release from the Food Standards Agency here. It says

You can get ill if you eat unbaked dough or batter made with flour containing bacteria. Flour is a raw ingredient and should be cooked or baked before eating to make it safe. …

It is particularly important for vulnerable people, such as children under 5, … to not taste or eat raw dough or batter. This is because their immune system may not be able to fight off infections as easily.  

Foods to be careful with include dough or batter for foods like cookies, cakes, pie crusts, pizza, biscuits and pancakes. Also, crafts made with raw flour, such as homemade play dough can be risky. Ensure you clean hands, surfaces and utensils after use to avoid cross-contamination.


According to UK Flour Millers (the industry trade body),

The microbial content of white flour is lower than that of wheat itself as microorganisms reside on the outer bran layers of the wheat grain which are removed during the milling process.

There is also a robust monitoring procedure in place.

Whilst there are no legislative levels for microorganisms in flour, UK flour millers take great care to ensure that the food they produce is safe.  In order to do this, UK Flour Millers members fund a monitoring programme that closely examines the microbiological content of flours.  Since 1971, an annual survey of the microbiological condition of white flours has been carried out using samples from UK Flour Millers members’ mills, representing flours from across the country.  This continues to show that the microbial content of UK flour is low.

But although the risk is very low and it is not something we should worry about over much it is also not something that should be dismissed.

According to records from the CDC in the US, they investigate E. coli or Salmonella outbreaks linked to raw flour roughly every other year. Over the last 20 years, outbreaks in the USA resulted in 752 cases of reported illnesses, 30 percent of which required hospitalization. In Germany, testing has shown regular, low-level contamination of flour but there do not seem to have been any outbreaks. We can find no sign of any cases here in the UK.

What to do? 

It would seem sensible to use white flour rather than wholemeal. And, as suggested by the FSA, best way to deal with this is to heat treat the flour before use. The article does give a couple of methods – either empty the flour into a baking tray and bake it or do something similar in a dry frying pan.

In our view, though, these methods do seems a little fiddly. The article mentions that you need to get the flour to  70C for 2 minutes. Here at SSERC, we investigated the effect of simply putting the unopened bag of flour in the oven. Flour is a fairly good insulator but we found that the centre of a 1.5 kg bag reached 70C after 2 1/2 hours at 100C. (We kept the temperature down to ensure the paper didn’t char or the flour get affected)

So an easy solution would be to place unopened bags of flour when bought in an oven at 110 – 120C for 3 hours. This should ensure the temperature reaches at least 70C and be sufficient to kill any food-poisoning bacteria – if any are present at all. The bags can then be keep it in an airtight container until use. It shouldn’t be too onerous a system to set in place.

The same procedure will apply for cornflour and any other flours – although smaller -packets will require a shorter time.