Homebrew Beer Blog

I pitched 23g of W-34/70 last night. I was a little surprised at the detailed procedures for rehydrating yeast. It got me thinking whether some of the criticisms of dry yeast may be because of the yeast, or just not following instructions.

Originally, I was just going to dump it in there. I figured I was using a lot of yeast and rather than risk contamination, just go with it. I’ve read some interesting opinions against rehydration, but then I went to Fermentis’ site and figured I better hydrate.

Re-hydrate the dry yeast into yeast cream in a stirred vessel prior to pitching. Sprinkle the dry yeast in 10 times its own weight of sterile water or wort at 23C & 3C. Once the expected weight of dry yeast is reconstituted into cream by this method (this takes about 15 to 30 minutes), maintain a gentle stirring for another 30 minutes. Then pitch the resultant cream into the fermentation vessel.

Alternatively, pitch dry yeast directly in the fermentation vessel providing the temperature of the wort is above 20C. Progressively sprinkle the dry yeast into the wort ensuring the yeast covers all the surface of wort available in order to avoid clumps. Leave for 30 minutes and then mix the wort e.g. using aeration.

So, we have two options here. Going directly into wort so long as it’s above 68-degrees, and that it is left alone for 30 minutes, then mixed in. Second option is the rehydration, and I was surprised at the steps. I figured it would be like baking yeast, and just put it in some hot/warm water for 15-20 minutes and call it good. I think the lower temp is interesting, so not to cause temp shock, but also the time involved.

What I did was treat it like a starter, but with water. I boiled some water in a 500ml flask, then chilled it in the sink down to mid-70s, then pitch the yeast. I had a small stir bar in there, and I put it on the stir plate for about an 45 minutes. Then I pitched into the lager wort at 48-degrees, set the heater to heat it up to 52 for fermentation. I’m a little concerned about temp shock, but what are you going to do…

Now, with the lager yeast, it gets a little more interesting… For the pitching rate:

80 to 120 g/hl for pitching at 12C & 15C. Increase dosage for pitching below 12C, up to 200 to 300 g/hl at 9C.

So, lets call it 100g/hl or about 20g per 5 gallons. Notice that’s how much you’re supposed to be pitching at 54 degrees. Since I pitched at or below 48, I should have pitched 2 to 3 times more!

So, basically it seems I should be either pitching at exactly my fermentation temp at my rate w/ rehydration or pitch directly into warm wort following those directions. In the case of lager, then I will have to chill it down from 68 to 52 in a matter not to harm the yeast, but also not hard the beer. If I don’t follow these steps, it would seem I would be underpitching. From the general rep of dried yeast, there may be a parallel with the side effects of under pitching. Thoughts?