Explainer: Why do bananas make everything around them smell like bananas?

A hardcore investigation from taste.com.au, plus tips on how to prevent it.

Kelly Pigram

3 min read

May 30, 2024 - 12:29PM

bad-banana

We’ve all been there: you open your beautifully packed lunch box or backpack at lunch, unwrap a sandwich and low and behold… The entire thing smells and tastes like banana. Along with everything else in the near vicinity.

What is it about this fruit’s smell and taste that travels so easily? Here at taste.com.au, we’re pretty into science and weird food facts, so we decided to investigate the phenomenon – and figure out a way to fix the smell without not packing a banana in your lunch (because they’re too good to go without).

To find out, we spoke to Nisharnthi Duggan, a chemistry PhD candidate from the University of Sydney with a special interest in food. She had some answers.

Why is the smell of bananas so strong?

“When bananas ripen, they produce a range of smelly chemicals known as ‘esters’. These types of chemical compounds are responsible for many fruity smells and flavours that we regularly encounter,” Duggan says.

“A few different esters contribute to the banana smell, but the most distinctive is called ‘isoamyl acetate’. The reason that the smell of banana is often so strong and can be transferred to objects or food close to it is that isoamyl acetate is volatile.”

This means that once it’s in your bag, the smell of banana readily evaporates into the air and travels around – making it easily detectable by our nose.

“This is similar to the way that perfumes contain nice-smelling volatile compounds which evaporate into the air, so when you are standing near someone wearing perfume you can smell it.”

But why do bananas make everything smell like bananas?

When you have a banana in your lunch box, that super volatile isoamyl acetate evaporates into the air of the lunch box and sticks to other items, which our nose can detect later.

“As the banana continues to ripen,” Duggan adds. “It produces more isoamyl acetate, that’s why more ripe bananas tend to smell more strongly.”

So the riper the banana, the worse the smell. This has a scientific purpose, too, according to Russell Keast, a Professor at Deakin University’s CASS Food Research Centre. He says that the “overpowering” smell is a signal to us from the fruit that we should be eating it, now!

“Volatile aromas generally serve a purpose for the fruit,” he says. “In this case, it is to attract people or animals to eat it. In doing so, we consume the seed that can travel through our digestive tract and be seeded for another plant to grow and therefore perpetrate the life cycle of the plant.”

How do you prevent the smell from spreading?

Unfortunately, if you like to eat ripe bananas, there’s not much you can do to avoid the smell of them getting into other things in close proximity. But Nisha says there’s one thing you can do: try and choose slightly less-ripe bananas, which will have smaller amounts of isoamyl acetate.

“Separating your bananas from each other could help prevent them ripening – and getting smelly – too quickly,” she explains. “Wrapping a banana separately in the lunch box in foil may help to prevent the isoamyl spreading too much but is unlikely to prevent it completely.”

But there’s one small benefit to the gas…

“As well as these smelly esters, bananas also produce ethylene gas, which is a ‘plant-ripening hormone’,” Duggan says. “This means that when other fruits are kept close to bananas they ripen faster.”

So there’s some scientific evidence to that whole ‘put a banana in a bag with your avocado’ thing. Who knew? What food science facts should we investigate next, readers?

Meet Australia’s #1 banana bread recipe

If you don’t want your overripe bananas to taint everything, we know exactly how to use them: banana bread, aka the sweet treat invented to make use of rotting bananas. Banana bread NEEDS bananas that have had better days so don’t throw them out!

This recipe is super simple to make and uses ingredients like cinnamon, brown sugar and molasses that complement the sweet bananas oh-so-beautifully. And It only takes 15 minutes to prepare so get to it.

You can check out the recipe HERE.

Banana bread

Our best banana recipes (that don’t smell):

Originally published as Explainer: Why do bananas make everything around them smell like bananas?