It’s a question that occasionally catches people by surprise.

You store a loaf in a beeswax bread bag. Several days later, the bread is still remarkably soft - but there’s a patch of mould on it.

If the bread bag is keeping the bread fresh, how can it be mouldy?

The answer comes down to an important distinction: staling and mould growth are not the same process.

What beeswax food storage actually does

Beeswax wraps and bags provide a protective, breathable covering for food.

When used for bread, they can help reduce moisture loss and protect the loaf from the surrounding environment. That can help bread remain soft and enjoyable for longer than if it were simply left exposed.

But beeswax food storage isn’t a preservative.

It doesn’t sterilise the bread, and it can’t guarantee that mould spores won’t grow.

That means it’s perfectly possible for a loaf to remain soft while simultaneously developing mould.

Why does bread go mouldy?

Mould is caused by fungi, and microscopic mould spores are all around us. They may already be present on the bread, or they may come from the environment.

Give those spores suitable conditions and they can grow.

Moisture, warmth and time all play a part. The bread itself matters too.

A moist loaf without preservatives may behave very differently from commercially produced sliced bread containing preservatives. Two loaves stored in exactly the same way can therefore have quite different lifespans.

Temperature and humidity in your kitchen can also change the equation.

This is one reason we’re wary of claims that any food wrap or bread bag will keep bread “fresh for X days”. There simply isn’t one number that applies to every loaf and every home.

Breathability is important

There’s a balancing act involved in storing bread.

Leave bread completely exposed and it can dry out quickly. Seal moisture into the wrong environment and you may create conditions that encourage mould.

Beeswax food storage is designed to provide a breathable covering rather than an airtight plastic seal.

That makes it particularly useful for bread - but breathable doesn’t mean mould-proof.

How to reduce the chance of mould

Always allow homemade or freshly baked bread to cool completely before wrapping or bagging it. Putting warm bread away can introduce additional moisture.

Store it in a cool, dry place away from direct sunlight and heat.

And consider how quickly you realistically eat a loaf.

If it normally takes your household a week or more, storing the entire loaf at room temperature may not be the best option regardless of what it is wrapped in.

Instead, keep a few days’ worth in your beeswax bag or wrap and freeze the remainder while it is fresh.

What should you do if bread goes mouldy in a beeswax bag?

Discard the mouldy bread and give the bag a good wash in cool water with a little dishwashing liquid.

Rinse it well and allow it to air dry completely before using it again.

A mouldy loaf doesn’t automatically mean the beeswax bag itself needs to be thrown away.

The important distinction

Beeswax wraps and bags can help food stay fresh, but “fresh” doesn’t mean preserved indefinitely.

With bread, one of their useful jobs is reducing moisture loss and helping prevent the loaf from drying out too quickly. They don’t contain a magic anti-mould force field - much as we might like our bees to have figured that one out.

If your loaf is still soft after five or six days but eventually develops mould, that doesn’t necessarily mean your beeswax storage has failed.

It may actually tell you that it has done one part of its job very well: the bread didn’t go stale first.