Adding frozen berries to your breakfast? Food safety experts say there's a step you shouldn't skip

A handful of frozen raspberries or blueberries can make an ordinary bowl of yoghurt feel a little more special. They're convenient, easy to keep in the freezer and a simple way to add fruit to your breakfast, especially during the colder months.

But before you tip them straight from the bag onto your yoghurt, there's something worth knowing. Frozen fruit can sometimes carry viruses that cause illness, and putting it in the freezer doesn't necessarily make those viruses disappear.

Food safety authorities have raised concerns about this for years. So, should you be treating frozen berries differently from fresh ones? And does it matter how you plan to eat them?

Why frozen berries can sometimes carry viruses

Berries grow close to the ground and are often handled at several stages before reaching the supermarket. If they become contaminated during growing, harvesting, processing or handling, viruses can end up on the fruit.

According to the Voedingscentrum, hepatitis A is one of the viruses that can be transmitted through contaminated food. Frozen berries have been linked to outbreaks because the virus can survive freezing. Washing the fruit doesn't reliably remove all viruses either.

Norovirus is another concern. It can cause vomiting and diarrhoea, and contaminated fruit can be one way it spreads. This doesn't mean every bag of frozen berries is unsafe, but it does explain why food safety agencies take the issue seriously.

Frozen berries have been linked to outbreaks

This isn't just a theoretical risk. In January 2025, the Dutch RIVM reported a hepatitis A outbreak linked to frozen blueberries. The virus was detected in two packages of a specific one-kilogram product.

That warning concerned the product involved in the outbreak, not every frozen berry sold in the Netherlands. Still, it showed how contaminated fruit can reach consumers even after spending time in a freezer.

Ireland's Food Safety Authority had already issued advice on the issue back in 2013, following a hepatitis A outbreak associated with imported frozen berries. Its guidance remains that imported frozen berries should be boiled for one minute before they are eaten. The FSAI explains the recommendation here.

What should you do before eating frozen berries?

The Irish advice is specific: imported frozen berries should be boiled for one minute before consumption. It isn't a blanket instruction covering fresh berries or fruit you've picked and frozen yourself.

Dutch guidance is a little more nuanced. The Voedingscentrum explains that hepatitis A can survive freezing but is killed by heating. If you want to avoid the risk, heating the berries is the sensible option.

This is particularly worth considering for people who may be more vulnerable to foodborne infections, including young children, older adults, pregnant women and people with a weakened immune system.

Does this mean changing your breakfast routine?

Not necessarily. It mostly depends on how you use your frozen fruit.

If you're adding berries to porridge, cooking them into a compote or using them in a crumble or cake, they'll already be exposed to heat during preparation. The question is more relevant when you're eating them cold.

That includes sprinkling frozen berries directly over yoghurt or muesli, using them as a cold dessert topping or blending them into a smoothie without heating them first.

If you're following the FSAI advice for imported berries, boil them for one minute, then allow them to cool before adding them to your breakfast. Frozen fruit can still be a convenient way to enjoy berries throughout the year. It's simply worth knowing that the freezer doesn't necessarily make them ready to eat straight from the bag.