Q: If I open a box of berries and one berry is mouldy, do I need to throw out the whole box?
A: Fresh strawberries, blueberries and blackberries are among our favourite fruits, but their goodness can be fleeting. Within a few days of bringing them home from the farmers market or supermarket, it’s common to find that some grey or white fuzz has staked a claim to a berry or two, prompting many to wonder: Are the rest safe to eat?
Food safety experts say that while you shouldn’t eat berries that are obviously mouldy, those without visible signs of the spores are fine to eat. And luckily, unlike other food safety concerns that may be invisible to the naked eye, berries with mould growth are easy to spot, said Benjamin Chapman, a professor and food safety specialist at North Carolina State University. (Botanically minded readers may note that many fruits commonly known as berries, including strawberries, raspberries and blackberries, aren’t true berries, but we will describe them as such for the sake of simplicity.)
If his basket or clamshell is tainted by one or two mouldy berries, “I don’t throw out the whole thing,” Chapman said. Instead, he tosses the mouldy ones and carefully inspects adjoining berries for fuzz, which often appears around a bruise or the site of stem attachment. With the rest, he tries to eat them soon, because lingering mould spores may spread and develop more fuzz in a day or two.
Moulds are a type of fungi that, when viewed under a microscope, often “look like skinny mushrooms,” according to the US Department of Agriculture. They grow threadlike roots that invade the interior of the food, and tiny stalks topped with spores on the surface. Certain types of moulds produce toxins that can be harmful if eaten, and in some people, moulds can trigger allergic reactions, Chapman said.