# Diacetyl Rest?



## yum beer (14/4/11)

I have seen mentioned many times in different treads about a 'diacetyl rest'
I am not familiar with the term.
what exactly is it, and is it necessary?
cheers
:icon_cheers:


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## Pennywise (14/4/11)

It's not always necessary. Basically diacetly is a by-product of fermentation, which lends a buttery taste & a sometimes slick mouthfeel, it is mostly produced at the start of fermentation. Generally Lagers are more prone to diacetly (lower ferment temps) which can be cleaned up by upping the temp a couple of degrees above ferment temp. Diacetyl is one of the reasons we want a relative quick start to fermentaion, as a longer lag time generally means the yeast will produce more diacetyl than it can clean up after the ferment. Can also be from infection as well

A few threads on the issue here


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## Bribie G (14/4/11)

I currently have a pale ale on tap that I pushed through rather too quickly and it's distinctly diacetyl. I like diacetyl and usually quite pleased when I get it, but it doesn't go well in a lager.
Get a packet of Werthers old fashioned butterscotch drops and suck one. That's diacetyl.


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## Brewing_Brad (14/4/11)

BribieG said:


> Get a packet of Werthers old fashioned butterscotch drops and suck one. That's diacetyl.


My question is; how do you pronounce the word? It's one of them I've only ever seen written down. My guess is die-a-set-til. Close?


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## Pennywise (14/4/11)

I pronounce it dia-see-til? No idea if I'm correct though


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## felten (14/4/11)

die ass et ull


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## yum beer (14/4/11)

cheers guys,

i have been doing this recently, not really sure why.
At least now I understand why. :blink:


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## Brewtus (14/4/11)

Die Seat L

is the best to my knowledge. If you want beer with a shot of butterscotch snaps in it, it's the way to go. Had some Vienna lager tonight at a BJCP course that was full of it.


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## Phoney (14/4/11)

I dont mind a good quality chardonnay with a distinct diacetyl after taste..


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## Wolfy (14/4/11)

BribieG said:


> Get a packet of Werthers old fashioned butterscotch drops and suck one. That's diacetyl.


I quite like how those taste ... might have to abuse my yeast a little more often.


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## fawnroux (15/4/11)

phoneyhuh said:


> I dont mind a good quality chardonnay with a distinct diacetyl after taste..



Is it actually diacetyl? I love chardonnay, and 'butter' is commonly on the palette. When I started brewing and learnt about diacetyl, I remember thinking "hmm, I wonder if this is what is in chardonnay". So, is it something the winemakers look to put in a chardonnay on purpose with the yeast management?


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## HoppingMad (15/4/11)

:icon_offtopic: 
Useless fact on diacetyl - It's actually used in food processing of cinema popcorn to give it a butter flavour.

Second useless fact - vapours from this diacetyl in factories can be fatal and can cause lung disease and bronchitis. 
Plenty of class actions are happening on the US from workers and US attorneys are making a chunk of money out of a condition called 'Popcorn Workers Lung'.

However it's not supposed to be bad for us folks in brewing & wine making land due to the low concentration. (diacetlyl is commonly found in many english ales, and chardonnays).

Back on topic:

I find doing a diacetyl rest tends to actually get rid of sulphury smells from lagers more than removing buttery diacetyl flavours. But if you do the rest correctly, you will have a beer in a day that starts smelling like real beer again instead of a rancid skunk fart. So they are great things to do.

Some European Commercial Breweries actually don't do Diacetyl rests on their lagers - learned this fact from Chris White of White Labs during his talk at ANHC. The breweries that don't do them simply have a very long lagering period instead.

Hopper.


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## unrealeous (15/4/11)

felten said:


> die ass et ull


This is the way I believe its pronounced.

View attachment diacetyl.wav


You can have fun trying to get it to sound the way you think it should be at http://www2.research.att.com/~ttsweb/tts/demo.php


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## [email protected] (15/4/11)

I always assumed it was a hard C noise,

di- ak- til,

Guess I was way off.


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## manticle (15/4/11)

Think of acetone mate.

Same with acetaldehyde.


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## Phoney (15/4/11)

thefawnroux said:


> Is it actually diacetyl? I love chardonnay, and 'butter' is commonly on the palette. When I started brewing and learnt about diacetyl, I remember thinking "hmm, I wonder if this is what is in chardonnay". So, is it something the winemakers look to put in a chardonnay on purpose with the yeast management?




Yep.




> The makers of some wines, such as Chardonnay, deliberately promote the production of diacetyl because of the feel and flavor it imparts. It is present in many California chardonnays known as "Butter Bombs," although there is a growing trend back toward the more traditional French styles.[citation needed]
> 
> 
> Concentrations from 0.005 mg/L to 1.7 mg/L were measured in chardonnay wines, and the amount needed for the flavor to be noticed is at least 0.2 mg/L.[4][5]



http://en.wikipedia.org/wiki/Diacetyl

It makes me feel like a connoisseur (wanker) when I do wine tasting tours I mention the diacetyl flavour in chardy's. :lol:


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