Why Do Some Wheat Beers Taste Like Banana?

Have you ever taken a sip of a wheat beer and thought, why does this taste like banana?

There’s a good chance there isn't a banana anywhere in the brewery.

This is particularly common with German style wheat beers such as Hefeweizen. You can get aromas of ripe banana, banana bread, bubblegum and even a little clove. And all of this can come from the yeast.

When we brew a wheat beer, the ingredients themselves are fairly simple: malted wheat, barley, hops, water and yeast. There may be no fruit involved at all.

So where does the banana come from?

It starts with the yeast

Yeast has a much bigger role in beer than simply making alcohol.

During fermentation, yeast converts the sugars in the wort into alcohol and carbon dioxide. But while it is doing that, it also produces hundreds of other compounds that contribute to the flavour and aroma of the beer.

One group of these compounds is called esters.

Certain wheat beer yeast strains are particularly good at producing them. One of these esters, isoamyl acetate, has a very familiar smell: banana.

And this is the slightly strange part. You give the yeast malt, water, a comfortable temperature and enough sugar to keep it happy. A few days later, you can have a beer that smells like ripe banana.

We didn't add the banana. The yeast just decided to make something that smells like it.

But what about the clove?

If you've had a traditional Hefeweizen, you may have noticed that the banana isn't always alone.

There can also be a spicy, clove like character.

That comes from a different compound called 4 vinyl guaiacol, which is produced by certain wheat beer yeast strains during fermentation. The balance between banana and clove is one of the things that makes wheat beer yeast so interesting. Change the yeast strain, fermentation temperature or other aspects of the fermentation, and you can end up with a very different beer.

One wheat beer might lean towards ripe banana and bubblegum. Another might be much more spicy and clove driven. The ingredients can look almost identical on paper, but the yeast can take the beer in a completely different direction.

So should wheat beer taste like banana?

It depends on the style.

A traditional Hefeweizen can have a noticeable banana character, but it shouldn't taste like someone poured a banana shake into your pint. It is usually part of the overall aroma: ripe banana, a little sweetness, some clove, wheat and that slightly soft character you expect from the style.

And that's one of the things I enjoy about brewing. We control quite a lot of things in the brewery. The ingredients, the temperature, the recipe and the process. What the yeast decides to do with all of it is another matter. So the next time you pick up a wheat beer and get that banana aroma, don't look around for the fruit.

It's probably just the yeast doing what it does best.