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[MtnBrewer]

Cold Pitching Yeastcontributed by cj in jQ: What is cold pitching?A: It's just like it sounds. Instead of taking your yeast out of the fridge and warming it up to room temperature, you keep it in the fridge until it's time to pitch it. Take it out of the fridge and pitch it directly into your cooled wort.Q: What are the benefits of cold pitching?A: Cold pitching gives quicker starts with less lag time (2-4 hours typically), more vigorous fermentations (I generally need a blowoff tube), quicker finishes (3-4 days max for low to medium OG beers), complete fermentation (near or above the high-end of attenuation figures for a given yeast), and healthier yeast for harvesting (I've gone up to 5 generations with the same yeast and probably could have gone quite a few more).Q: Tell me more!A: Cold pitching of yeast works best with harvested yeast. To harvest yeast, after transferring your beer from primary, either leave a pint or so of beer behind or have some pre-boiled cool distilled water to add to the yeast. Swirl to get the yeast in suspension, pour it into a large glass container (I use a 2-liter erlenmeyer flask, but any large glass jar/bottle is fine), cover the top with sanitized aluminum foil, and put it into the fridge. Make sure it doesn't freeze. Ideally you should brew within the next day or two, but definitely within a week. Keep the harvested yeast in the fridge until you're ready to pitch it into your new wort. Again ideally, the wort should be ~5F lower than your target fermentation temperature. Pour off the liquid on top of the yeast, leaving just enough behind to liquify the yeast. Swirl and pitch 250 ml (1 cup) to 400 ml (about 1.5 cups) into the new wort, depending on the original gravity. Aerate as well as you can, swirl to mix the yeast into the wort, seal the fermenter, and stand back! In most cases, fermentation will start within 2-4 hours, with vigorous fermentation starting within 6 hours.Q: I can't get my wort that cool with my immersion chiller. Does that mean I can't cold pitch?A: No, you can still do it. Until recently, I used an immersion chiller and couldn't get my wort chilled to under fermentation temps. I've used the cold pitching technique in beers as warm as 79F, which I then continued to cool down with ice bottles strapped to the fermenter. Even with this continued cooling, I had lag times of only 2-4 hours.Q: I normally don't harvest yeast because I like using a different yeast for each beer. Does that mean I can't cold pitch?A: No, again you can still do it. I said ideally it should be used with harvested yeast. However, when I make a starter, I follow the same basic cold pitching procedure. Once the starter is fermented out, I put it in the fridge and cold pitch the next day. Lag time is generally an hour or two longer, but everything else proceeds as usual.Even with normal-sized starters, you can benefit from cold pitching. One time several years ago, I experimented with a small (50 ml) Wyeast pack. I made a 1-liter starter with 110 g DME -- forgot the yeast nutrient. On Sunday I put the starter into the fridge in preparation for Monday's brewing.On Monday I brewed. OG was 1.053. I aerated with an oxygen pump for 45 min (as usual), pitching the yeast slurry directly from the fridge 40 min into the aeration. I decanted most of the liquid off the yeast, and then swirled to get it back into suspension and pitched. The wort temperature was 79F when I pitched, and I put frozen bottles of ice around the fermenter to get it down to my desired fermentation temperature of 68-70F.Three hours later I opened up the pressure release and put the airlock on. Fermentation was already going strong. Temperature at this point was still 76F so I continued cooling the fermenter. At six hours, the wort was down to 73F, and at nine hours it was down to 70F -- all in all, it was a fairly quick drop, but fermentation was steady and strong. In the morning (at 14 hours), temp was still holding at 70F and fermentation was vigorous. When I got back home late afternoon (approx 24 hours after pitching), I had to put on a blowoff tube (and clean up the mess). Temp was holding at 70F.Q: Do commercial breweries use cold pitching?A: Yes, that's where I found out about it. I was helping my friend in his brewpub and he taught me about cold pitching. He got the idea from a post on the Association of Brewers Internet forum where a brewer at a major macrobrewery explained about the technique. The technical information I've been able to find out about cold pitching is summarized below.1. There doesn't appear to be any published research about it. It seems that it's based on practical experience rather than any earth-shattering new discovery. It seems like a number of breweries have been doing this for a long time.2. The reasons for storing yeast cold are: 1st, the beer has no nutrients left for the yeast to use; 2nd, at 34F the yeast are slowed down and aren't damaged by being too cold (lower than 34F and they may freeze and die, higher and autolysis may start).3. The optimum condition (for both lagers and ales) is to pitch 34F yeast into wort that is 3-5F BELOW your target fermentation temperature. The yeast quickly warm up to the wort temperature, and begin taking in nutrients and oxygen from the wort. That process produces heat which brings the yeast up to fermentation temp. In other words, the yeast are happy to change from their rest phase at 34F to their active growth phase at your fermentation temp minus 3-5F. Pitching yeast into warmer wort and then cooling it to fermentation temp may interrupt or slow down the growth phase, resulting in longer lag times.4. When preparing a starter, do it at fermentation temperature and once the starter is done, cool it down to 34F.There's a lot more interesting information here and at Northern Brewer (search for cold pitching). But the best advice I can give is to try it for yourself -- that's the only way you can really understand the beauty of cold pitching! smile.gif As for me, I haven't pitched yeast warm for three years, and I don't see that changing anytime soon![4/11/06 Edit -- I actually did pitch a yeast warm at high krausen a couple months ago, just because I got a late start on my brew week. It worked fine, but I stand by my "beauty of cold pitching" comment above.]