Thursday, March 21, 2013

Two Factors For Better Attenuation

I enjoy my beers on the dry side and regularly use well attenuating yeast to ferment with for the most part. My go-to's are Safale US05, and Whitelabs Wlp001 and Wlp500, but on occasion I will still end up with beer that is under-attenuated as the yeast leaves behind unfermented sugars when it drops out of solution and goes dormant.

I scratch my head confused and frustrated by these results after feeling like I made sure I did everything right. My fermentation temperatures were within the optimum range and consistent and the wort was well aerated. I'm convinced that all of my brewing practices were perfect for a complete conversion only to be disappointed when the yeast wasn't able to complete its task. But there were a couple lessons that I had not learned yet and they needed to be addressed.

Two main reasons that under attenuation occurs that I wasn't considering with the seriousness that it deserved was the accuracy of my mash temperature and the level of my mash ph.

The importance of strike temperature
I often took a careless approach to the important effects of mashing at either too high or too low a temperature which can either limit the effectiveness of one of the essential enzymes and or denature and stop other enzymes from effectively breaking down starches into simple sugar molecule chains, something the yeast is relying on us as brewers to execute well, for their ease of metabolism.

I am now very careful about getting my mash temperature to within a degree or two at the beginning of the mashing time. My strike water temperature for the grain to water ratio that I use is 166-168f. which leaves me with a consistent rest temperature of 149-151f. Knowing this, I can achieve a slightly more fermentable wort by lowering my strike temperature by a couple degrees or raising the temp. for a slightly less fermentable wort. But I still regularly confirm a proper mash temperature after thoroughly mixing in the grist. I do this by comparing my mash tun thermometer for accuracy on occasion to make sure I'm getting proper readings. This is achieved by taking the temperature of the mash with another thermometer, one that I know is accurate. I stab down into the mash from above, moving around to different areas of the grist, I then compare this reading with the built in thermometer, essentially getting a consensus from the two readings.

The importance of mash ph.
The other factor that effects yeast and one in which I paid little attention is mash ph. A mash ph. that is alkaline or above the optimum 5.2 to 5.7 range will again effectively leave you with long chains of sugar in the wort as the beta amylase enzymes work best is an acidic environment. An alkaline environment limits this enzyme activity thus leaving the yeast with a difficult time of metabolizing.
When brewing with hard water, relying on the grain bill to lower the mash ph. may not be enough and so other steps must be taken. A couple simple solutions would be to dilute the brewing liquor with distilled or reverse osmosis filtered water essentially softening the water, adding calcium in the form of gypsum and/or adding acid to the mash.

A dry beer ready to be drunk
The importance of these two influences in starch conversion should not be overlooked and if you are finding that your beers are coming in with low attenuation, should be considered as primary factors to investigate.

Now that I carefully manage these two areas during my brewing session I have been able to consistently achieve proper attenuation from my yeast and effectively manage the outcome of the remaining sugars depending on the style of beer I want. Cheers!

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