Yeast Question

[GunNut76]

Okay, I'm gonna nit-pick here...Say I have a yeast that has an optimum temp range of 65-72 and I ferment at 74...Does two degrees make THAT much of a difference? I know you can point out that water freezes at 32 and not at 34, but yeast is a living thing and so am I. I know that I can't tell the difference between 70 and 72 so why should the yeast? Somebody please enlighten me on this subject.

[brewmonkey]

Small temp changes like that will effect the way the yeast work and thus change the flavor of the finished product. Small changes like you are talking about, 2 degrees, may not make much of a noticable change to most of us but it will be noticed by the some.

In the brewhouse my primary strain was the same for 80% of the beers I produce. I could tell the difference over 2-3 degrees (even in the optimum range) in temp.

This is a fun project to do also. Brew the same beer and change the temp of the fermentation if you have the ability to. Then have some one administor a blind taste test and see if you can note the differences. You will be suprised at how much you do notice.

[evilredlight]

what about 2 degrees under?
at 63 degrees instead of 65
will it still ferment, just slower?

If it is a big problem I need a way to raise the temp a few degrees for fermenting
I am a student in canada, and I am fruggle with heating house, we use sweaters instead.

maybe I should switch to lagers for the winter!

[brewmonkey]

Going lower will certainly affect the metabolism rate of the yeast and the way they ferment. Cooler temps would produce less esters/flavors and most likely give off more of the sulfur compounds normally associated with lager production. You should also expect to see longer lag time as well as longer primary fermentation time and conditioning period.

[Fast_Eddy]

Also seems that lower yeast metabolism can result in more diacetyl persisting into the end product - depending on the strain.

[brewmonkey]

Originally posted by Fast_Eddy
Also seems that lower yeast metabolism can result in more diacetyl persisting into the end product - depending on the strain.

If you notice that you are getting more diacetyl then you believe you should be, before racking to secondary raise the temp to as close to 68F as you can and hold it for 24-48 hours. This is a diacetyl rest and if it was produced by the yeast it will reabsorb the vast majority of it. If it is a bacterial caused diacetyl, you're stuck with it.

Diacetyl rests should be conducted with all lager strains as well.

[evilredlight]

what is the taste of diacetyl, or how would I know if this was a problem?
I guess I have to find a way to get into mid-range!

[brewmonkey]

Originally posted by evilredlight
what is the taste of diacetyl, or how would I know if this was a problem?
I guess I have to find a way to get into mid-range!

Diacetyl will have a buttery/butterscotch aroma and flavor. Some people have a lower tolerance then others to it, but it is nasty when you do not want it there. Chardonnay wines are famous for this flavor. Grab a glass and taste it, that butter note you get on your tounge is exactly what diacetyl tastes like. Bleeeeech...

[Fast_Eddy]

Originally posted by brewmonkey
Diacetyl will have a buttery/butterscotch aroma and flavor. Some people have a lower tolerance then others to it, but it is nasty when you do not want it there. Chardonnay wines are famous for this flavor. Grab a glass and taste it, that butter note you get on your tounge is exactly what diacetyl tastes like. Bleeeeech...

I can stand just a hint of diacetyl in a bohemian lager. That's the only beer, to me, that benefits from a tiny amount.

[brewmonkey]

In some cases a beer missing diacetyl is considered a flaw. Alot of the Scottish and English brews may have diacetyl in a moderate amount as do some of the American Pale varities.

[Fast_Eddy]

Originally posted by brewmonkey
In some cases a beer missing diacetyl is considered a flaw. Alot of the Scottish and English brews may have diacetyl in a moderate amount as do some of the American Pale varities.

Seems to me that BJCP guidelines express that some diacetyl is acceptable for some brews but that it being absent is not a style flaw. I made a quick rescan of the style guide just now and the closest to diacetyl being a requirement would be a Wee Heavy and still it reads..."Moderate diacetyl character is also acceptable. " The rest of the styles read more like "...May or may not have hop flavor, diacetyl and fruitiness..."

[brewmonkey]

While they do state none-moderate for a good portion of them, those guidelines are not up to date or all inclusive. There are more styles out there then they cover, and every year that amount grows. They lack some of the recent incarnations that have been recognized by the IBS and now have their own categories at the GABF such as Double IPA's and Barrel Aged Beers.

[GunNut76]

So what will give a beer a banana flavor and nose? My irish ale has this and it still tastes OK, but it is annoying...it overpowers the subtle hop aroma I was trying to acheive.

[brewmonkey]

Usually those phenols are associated with the strains that Bavarian wheat's are made from (Weinstephan) as well as some of the Belgian strains.

What yeast did you use for this beer?

[fuji6100]

Diacetyl rests should be conducted with all lager strains as well.

Hmmm, I did not know this!

I have a lager fermenting away right now so I'll give this a try. Am I correct in assuming that after the diacetyl rest, I will rack to my secondary and then continue lagering at the previous temp (~50F is what mine is at now)

[brewmonkey]

After your primary is complete, bring it up for it's diacetyl rest (24-48 hours), when that is complete rack and then slowly start taking it down for its lagering period.

[GunNut76]

I used Wyeast 1084 Irish Ale. I was fermenting at 74 while the recommended temp range for 1084 is 62-72. This is what prompted the above question.

[evilredlight]

wyeast packs are all the same and say the same temp range for fermentation (saves print cost).
I have a brochure that takes all the separate yeast and tells you what their specific range is. Their webpage probable has the same info