Food Safety Risk Concerning Flour Contaminated by Escherichia Coli (E. Coli O121)


  From the Routine Food Incident Monitoring System, the Food Safety Department of the Municipal Affairs Bureau (IAM) had been notified of several cases in relation to flour contaminated by Escherichia coli (e.g. E. coli O121). Different places of origins have been involved in these cases, and therefore, the related products needed to be recalled and destroyed.


  Flour is one of the necessary ingredients used in a kitchen. For example, to make fried food, cakes, bread and sauces, it is necessary to use different types of flour. If we have mistakenly eaten food that is made from flour contaminated by E. coli, it is possible that we will get sick and have our health negatively affected. Escherichia coli (E. coli) is a bacterium generally found in the intestines of humans and animals. Most strains of E. coli are harmless, while some are pathogenic and may cause gastrointestinal illness in humans. The latter type of E. coli is called pathogenic Escherichia coli (pathogenic E. coli).


Why is flour contaminated by E. coli?

The outbreak of food-borne illnesses caused by flour is not common, but it is possible to happen. Once the ingredients of flour such as cereals are contaminated by animals’ excrement where pathogenic E. coli is found, it is possible for the germs to enter our food chain. A warm and damp environment is favourable for germs like E. coli. The heat which is produced in the process of grinding wheat is sufficient for the reproduction of germs, but it is unable to eliminate them. Furthermore, even a little water existed in the grinding machine or the storage of cereals can also constitute favourable conditions for growth. Moreover, E. coli is also capable of surviving in a dry environment, even when they are packaged in a flour pack.


What are the potential food safety risks in raw dough or batter?

  Currently, many people like making some small desserts such as cakes and cookies at home, but they may overlook some details in the process. Although we will not eat raw dough or raw batter directly, it is possible for children at home to eat them mistakenly when they help knead dough without paying enough attention. Raw dough or batter is often mixed with ingredients such as milk, water or eggs. The high amount of nutrition and water activity as contained in the mixture can provide E. coli with suitable conditions for survival and reproduction, if raw dough or batter is not stored properly. In the process of cooking food or kneading dough, flour may be dispersed around in the kitchen or on the utensils, but many people are not aware of the fact that flour can be the potential source of germs. Consequently, they do not clean and sanitise the surrounding places thoroughly after finishing their work, which may possibly result in cross-contamination.


Is it possible to disinfect flour before selling it?

  Flour can also be heat-treated like milk, to reduce germs, but the content of gluten will be destroyed. Bread made from such flour will not be chewy, and cakes made from it will not be fluffy.


What can residents do?

  • Vigilantly pay attention to news about food safety. In the event of recall of food products, please check the information of the related products at home and see whether the products match with the ones that are being recalled. Since the shelf life of flour is longer in general, residents may store the flour products which need to be recalled at home. In this case, such products should be discarded and the containers which have been used to store them should be thoroughly clean and sanitised.
  • Any products made from flour, dough or batter should be fully cooked/ baked before eating.
  • Hands, workbenches, and containers which have had contact with raw dough should be cleaned thoroughly.

  It is quite safe to make food products with flour, as long as we pay attention to food safety.