WhiteLabs WLP002

[Mike123]

I have brewed a couple of batches of a straight forward bitter using Whitelabs WLP002. The first time I used it I pitched it at 22°C and the first half of the fermentation was done at over 20°C. The second batch I brewed, the yeast went in at 18°C and I kept the temperature under 20°C which is the recommended temperature for the yeast. Problem is the first batch has some quite pleasant fruity flavours about it which I assume is down to the higher fermentation temperature? My friends also seemed to really like this. Would this yeast produce these flavours? Are they a problem as far as keeping quality of the beer is concerned? Do people ferment at higher temperatures to get these flavours anyway? I am about to set up a fermenter fridge so I hope to be able to repeat this. Could someone tell me what I am actually doing here? Am I producing esters or something else?

[Jocky]

The short version of my answer is that if you like the beer fermented at 22C with this yeast then ferment your beer at 22C! Brewing is very much about finding what works for you in your brewery.

Repeat brewing the same beer many times with a single change each time is a very powerful way of learning as you’ll taste the effect of every change.

A longer answer is that esters are created during yeast replication before fermentation and partially reabsorbed at the end. More yeast growth = more esters.

Things that can affect yeast growth:
- The amount of yeast you start with (fewer starting cells means more growth and more esters)
- Availability of oxygen (more aeration/oxygenation will reduce esters)
- Temperature (higher temperature means more esters)

You can manipulate these to adjust how your beer comes out, although if you push things too far you can end up with off flavours. Every yeast strain behaves a bit differently too, so it’s worth getting to know your house strain.

[MashBag]

Here you go...

Problem is the first batch has some quite pleasant fruity flavours about it which I assume is down to the higher fermentation temperature?
Yes.

My friends also seemed to really like this. Would this yeast produce these flavours?
Yes

Are they a problem as far as keeping quality of the beer is concerned?
No

Do people ferment at higher temperatures to get these flavours anyway?
Yes

I am about to set up a fermenter fridge so I hope to be able to repeat this. Could someone tell me what I am actually doing here...
Jocky covered that superbly.

[Mike123]

Thanks guys, that's really helpful as I was worried I was doing something wrong if the temperature went too high. Whereas in reality, it is just something else that can be tweaked to change the flavour of the beer completely!

[MashBag]

Absolutely. But tweaked with a 5-10°c (ish) range. Be guided by the manufacturer.
Yeasts start to fail much over 30°c and slow down dramatically in lower temps.

[Jocky]

It's worth getting to know a yeast by brewing with it a few times. Yeasts like WLP002 can be used for a big range of styles - bitters, blonde/golden ales, stout, even hoppy American IPAs. If you brew regularly it also means you can reuse the yeast between batches.