How berries become unsafe to eat
Some berries can carry harmful bugs, like:
- hepatitis A virus
- norovirus
- Shiga toxin-producing E. coli (STEC)
- Salmonella.
Harmful bugs can come from the farm where berries are grown. Sources can include:
- unclean water or soil
- infected workers and animals.
Food handlers, machines, and equipment can contaminate berries after they are harvested. The bugs can be spread during freezing, mixing, or packaging. This can make the berries unsafe to eat.
Making berries safe to eat
You can make frozen berries safe to eat by either:
- bringing them to the boil, or
- cooking them at a temperature over 85°C for at least 1 minute.
Washing frozen berries will not remove the risk.
Most viruses and bacteria found on frozen berries can survive freezing. They also can survive freeze-drying, and heat treatments of less than 85 degrees Celsius.
Frozen berries that have been heat-treated can be cooled rapidly and refrozen for subsequent use.
Video: Heat-treating frozen berries at home (1.46)
Transcript – show/hide
[Onscreen text] How to make frozen berries safe to eat.
Wash your hands with soap and water before and after handling frozen berries.
Method 1: Boiling
Bring to the boil for at least one minute
Or if you have a thermometer heat to more than 85 degrees for one minute
Method 2: Microwave
Stir halfway through to make sure berries are heated through
Cook berries until they are bubbling
Either use berries immediately or freeze for later use
Cool berries for at least 30 minutes before freezing
Once cooled pop into freezer for easy use
[End of transcript]
Some people are more at risk
Preparing berries safely is important when you:
- make uncooked foods that normally contain frozen berries, like smoothies and desserts
- serve berries to people with health risks.
People with health risks include:
- older people, especially those with underlying health conditions
- young children
- pregnant women
- people with low immunity.
Find out about food for people with low immunity
Find out more
Hepatitis A virus fact sheet [PDF, 203 KB]
Hepatitis A disease – Ministry of Health
Norovirus – Ministry of Health
Who to contact
If you have concerns for your health, consult your medical professional or phone Healthline at 0800 61 11 16.
If you have questions about the risks of imported frozen berries, email info@mpi.govt.nz
