Slow fermentation and off tastes?

[optaka]

Two quick questions that may or may not be related:

First, all three brews if have done have had a veeeery mild fermentation. I have done a coopers ale, a northern brewer irish red, and a brewers best irish stout and I have never gotten more than an inch of krausen and the bubbling out the airlock has always been rather slow. Active fermentation has always finished up within a few (3 or 4) days. Any idea why my fermentation would be so weak?

Second, I usually leave my beers to ferment for 3-4 weeks so that all the off flavors can be cleaned up. However, in both the red and the stout there has been a pretty distinctive diacetyl taste. A few weeks of bottling mostly took care of it for the stout, but much less so for the red. The difference could be due to the fact that the stout has more flavor and just covers it up better, but I'm not sure. What should I be doing to cut down on this off flavor?

 

[BrewinHooligan]

What are your starting gravities and fermentation temps? What yeast are you using and how much?

 

[optaka]

I have lost my notes on that stuff when I moved so I will be going off memory here and the instructions on their websites. I know all the starting gravities ended up lower than they were supposed to. The Irish red and stout were around 1.040 if I remember correctly. Both were fermented in swamp coolers with a water temp that hung around 70F or a tiny bit above. As far as yeast I couldn't tell you. Whatever came with the kits, I want to say Safale US05 in the Irish red, but that could certainly be wrong but 1 packet each. I know I added an extra packet of Coopers yeast on day 4 of the stout in hopes of kickstarting things. The red I tried rehydrating the yeast before I put it in, but not on the others.

 

[BrewinHooligan]

Some information I found researching online
"Diacetyl production and reduction are strongly influenced by temperature, and the rates for both increase as temperature increases. Thus, an ale fermented at 20 degrees C (68 degrees F) typically has a higher diacetyl peak than, say, a lager fermented at 10 degrees C (50 degrees F). The rate of diacetyl reduction, however, is much higher in the ale than in the lager, which is why most lager brewers prefer to get diacetyl levels below 0.10-0.15 mg/L at the end of the main fermentation. Some additional reduction occurs in cold storage, but at a very slow rate. For this reason, some brewers raise the temperature of a cold-fermented beer to 20 degrees C (68 degrees F) for a brief period following the end of the main fermentation, a practice that is usually called diacetyl rest."
Read the whole article here

I think your issue is one of fermentation temps. Try fermenting in the low 60's and then raise the temps towards 70 at the end of fermentation.

 

[optaka]

I think your issue is one of fermentation temps. Try fermenting in the low 60's and then raise the temps towards 70 at the end of fermentation.

That would be nice in theory, but not practical to do until the weather cools down. Any ideas on why my fermentation is so slow?

 

[BrewinHooligan]

A swamp cooler with rotating frozen water bottles will do wonders for your beer. Those times don't seem that slow IMO. Dry yeast usually takes a day or two to get going from my experience.

 

[helibrewer]

Pitch adequate yeast and control temperatures. Vigorousness means nothing..fast, vigorous fermentations are not necessarily good. How are your finishing gravities? A 70F swamp cooler for an ale is not too bad so unless you are getting big swings through the day, your temps seem ok.

Are you keeping consistent temps through the aging period? 3-4 weeks is plenty of time to get rid of diacetyl which leads me down the path of underpitching which shouldn't be with dry yeast and a 1.040 OG.

So...I'm thinking maybe that swamp cooler is not doing such a good job of temp control.