Friday, October 22, 2010

Death by Dunkel Update

A couple nights ago I decided to bottle the oatmeal stout and wanted to transfer the dunkel for secondary fermentation. It's been twelve days and looked like active fermentation had slowed. This was noticeable by the lack of bubbles in the airlock. To my surprise when I peaked in I saw this:

Looks tasty, right? :) I'm no expert, but the yeast still looked pretty active to me. I grabbed a hydrometer reading just to see where I was in terms of gravity. It was right around 1.019. The Kolsch yeast took about two days to get started. On the side of caution I decided to let the beer ferment for another couple days.

I'm not 100% sold on the notion of secondary fermentation. The trouble and time it takes doesn't seem worth it for every batch. The main reason I've decided to get the dunkel off the trub is to try my hand at harvesting the yeast by washing and storing for future use. More on that tomorrow. In the meantime I want to discuss the efficiency of my first true partial mash.

The Home Brewing Wiki provides a good background on efficiency and how it relates to both all grain and extract brewing:

In extract brewing, the malt extracts that are used to provide
fermentables always yield a predictable amount of sugar. A pound of LME in a
gallon of water will yield 37 points of specific gravity, and a pound of DME
will yield 45 points (give or take a point or two, depending on the brand of

For grain mashing, the story is different. Various types of
malt yield different amounts of sugars, and there are many other variables that
also influence how efficiently your mashing and sparging procedures extract
sugar from malt. Because of these factors, the amount of sugar obtained from a
pound of malt can vary over a fairly wide range. The good news is that as long
as your procedures remain reasonably consistent from batch to batch, it is
possible to predict how much sugar you will get from your malt, provided you
know what your extraction efficiency is. Extraction efficiency is the ratio of
the amount of sugars you actually obtain, to the theoretical maximum amount of
sugars available. Because of the large number of variables involved, the only
way to really determine the extraction efficiency of your brewing system is by
trial and error.

Typical extraction efficiency in a homebrew setting is
in the 60-80% range.

So considering 60% to 80% is the typical range for efficiency, how did I fair? Luckily I found an efficiency calculator thanks to the fine folks of Simply input your amount, gravity reading and ingredients to get the efficiency calculation:

Woohoo 83%!! It's still a little hard to believe considering it was my first attempt, but I guess I'm doing something right. I double checked all the ingredients input and I'm confident the hydrometer reading was accurate. I'm not going to argue... if I can consistently hit that mark I'll be a happy brewer. The only thing that confuses me is that I missed my OG by a couple marks. I would have assumed I would be dead on with that kind of efficiency.

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