For the last two plus years I have been simply re-pitching unwashed harvested slurry batch to batch similar to how a commercial brewery would harvest and repitch. I realize this is not a revolutionary technique, there are plenty of homebrewers who do this as well, but it's a technique I think that is being overlooked by a lot of homebrewers. It's a very simple process and actually has helped improve my beers and my knowledge of how a yeast pitch can evolve from generation to generation. Before I get into this keep in mind that I am not a microbiologist, so there may be some things that folks disagree with here but this practice has been tried and true over 40+ batches of my own beer, as well as in a commercial setting.
|A look down the carboy neck at some fairly clean slurry.|
With those two points in mind all the only equipment you really need is a vessel to store your slurry in. Mason jars work fine but I opt for something more fit for yeast storage in these Media Bottles or Polypropylene Jars. I like the media bottles best because both the lid and bottle are autoclavable, with the lid being polypropylene and the borosilicate glass container, so I can ensure the thing is super sterile by boiling or better yet using the pressure cooker. Not to mention this is a lab grade product and should last forever, assuming you don't drop it! The Polypropylene jars are great as well but I notice the rubber gasket can get gunked up over time, I tend to use those more for storing strains of Brettanomyces and mixed cultures where they spend more time in the jar being fed and will reside in for long stretches.
|This was, believe it or not, a pretty hoppy beer. Look how "clean" the slurry is.|
|The Alcohol lamp is there, i swear.|
|Once settled this was about 800ml of dense slurry.|
There is absolutely a benefit (see answer at the top of the thread):I already had this post mostly finished when I saw Neva say this and I am glad I waited to post it because this is useful information from someone smarter than I. Her point about the 2nd or 3rd generations being the most optimal is totally in line with my experience, but I would have said generation 4 was the sweet spot. It's nice to have some reassurance from a leader in the industry.
In general, yeast from a lab takes 2-3 generations before they are optimal condition for actual fermentations, so if yeast can be harvested well, you'll get some great yeast out of it.
It can take a few turns for the yeast to be completely acclimated to the fermentation environment, but once they are, performance is optimal around generation 3.
With a starter, its not that you're necessarily losing these benefits. While the yeast is not getting used to environments without oxygen (fermentation), you're still building up yeast metabolism and yeast activity so you'll get a faster, stronger start with a shorter lag.
Call me a romantic but I love seeing how the culture performs as those generations pass, sometimes the changes are good but there is a point of diminishing returns. You'll know when that time comes, it's been more of a gradual shift than an abrupt one for me. If you notice off-flavors (fusel alcohols, acetaldehyde, diacetyl etc) or under attenuation you should dump and get a new pitch. In the case of the 8 generation Wallonian pitch I had recently, I would have pitched it further but it got older than I wanted and decided to add it to a mixed culture that needed some extra Saccharomyces help. I think Wallonian was released in early 2014, and I've only bought two pitches in that time. With it being a Saison strain I'm not as afraid of some contaminations of LAB, Brett, or wild yeast as I would be my preferred hoppy beer strain Wyeast 1318.
As with any home yeast procedures it's inevitable that you will get some sort of contamination in your slurry, per Jamil Zainasheff on the Brewing Network most professional breweries do! There are some more advanced techniques including acid washing to clean up your culture if you want to go that route, I don't however I may try it just for the learning experience. Normally after 4-8 generations I am fine spending another $7-10 for a new pitch. I know it might seem a bit scary to do this, but give it a try at least once and see how you make out. One things for sure, you'll see active fermentation as fast as you've ever seen.