is it really what it seems to be? put fresh chilled wort into a fermenter with just previously used yeast? no need to wash the yeast? what is the time frame?
i know it seems like such a simple step, yet, i’ve not done this. it keeps popping up in some threads so i thought i’d ask about the process.
thanks & cheers!
Just think of it as a very large starter. Some people scoop out up to 2/3 of the cake so as to not overpitch, but in homebrew settings everpitching is not really an issue. I’ve poured onto a yeast cake many times before and it works great. Fermentation time frame is the same.
Yep. Lag timeframe is a different story! It will take off fast…
If you do not pull out some yeast, you should pitch a higher gravity beer.
Dave
I try to rack the first beer off the yeast as close to pitching time as possible. Generally, while the new beer is chilling I will rack the old beer to a secondary fermenter. Then I just dump in the new wort and aerate.
When I do this I try to keep the first beer at 1.050 or less (1.040 is better), and the next beer is at least 1.080 or so. If I’m pitching right on the cake, then I try to make sure the original beer is a similar style to the beer going on top of it. (i.e., APA to IIPA, a small Dubbel to Quad, Mild to Barleywine, etc.)
Dumb question from a newb here, but if you pour wort on an existing cake, doesn’t that mess with your sanitation?
You need to take sanitary precautions, but you are pitching sanitary wort onto yeast. The environment the wort is going into should be sanitary, you just have to make sure you arent introducing anything wild while transferring. If you are doing it pretty quickly and covering the yeast in between transfers you should be good to go.
I don’t see it any different than re-pitching yeast. Your fermenter should have been sanitized the first time so the real danger is introducing bacteria when you open it to siphon out or add the new wort. What I will do, and its working for me, is to brew a 5 gal batch of beer and then split that yeast into a new bucket so that I have 1/2 of the yeast as a “re-pitch” and 1/2 directly on the old cake. I only do this once because I do have sanitation concerns so I don’t continually re-use the same cake without a clean out. I do think that you will have some over-pitching concerns if you use the whole cake for an ale. And yes, it’s gonna take off like a rocket so be ready with a blow off tube if you are using a carboy. For a lager, I will put the wort on 100% of the old cake because I’ve been told you can’t really over pitch a lager.
The thing with washing yeast is that it is really not “washing”, it’s rinsing and you won’t remove any bacteria. In fact, if you’re not careful you can also introduce bacteria just like anytime you have the yeast open to the air. I’ve never done a true acidic wash and I don’t think too many people do.
Sanitation is not much of a concern, assuming the beer you had in there previously was sanitary. Over pitching definitely is. Also dead yeast cells are a concern. Also the braun hefe on the side of the carboy is a concern because it has some bitter and nasty flavor compounds you probably don’t want in your beer. Left over hop compounds might be an issue as well.
Unless you are going from a very low gravity beer to a high gravity beer (ordinary bitter to barley wine) I think you are much better off collecting the yeast slurry, using the pitching calc at www.mrmalty.com and approximating an appropriate pitch from there. You are better off pitching “the right” amount of yeast than overpitching, everytime.
Everything Keith says is correct, IMO. It’s so easy to just swirl the carboy and pour the yeast cake into a sanitized container that there’s no real reason to repitch into a gunked up carboy.
However, there’s no great harm in doing so and it will ferment and make beer.
You’re better off taking the extra step.
I don’t want to pitch a higher gravity beer
I frequently do this with my Mild’s and Scottish Ales.
I always harvest the yeast and wash and sanitize the container - but I collect and repitch multiple times, so I don’t want a whole slurry in there. I overpitched a light ale once and it was highly estery with US-05 slurry. I seem to recall that if the yeast don’t reproduce sufficiently, they instead throw off acetaldehydes or phenols, because their full reproduction cycle has been short circuited. I will defer to the science guys on that, but it makes sense to at least remove half of the yeast cake if repitching to a comparable or smaller beer.
thanks for all the input!
Definitely THE Science Guy!
A snippet from the Danstar page:
“High temperature early in fermentation decreases ester production. High temperature later in fermentation increases ester production”
This is the opposite of what I’ve always thought. Can some explain the reasoning behind this?
High temperatures early in the fermentation tend to increase fusels. Ester formation is caused by different factors and vary from strain to strain.
I think some brewers tend to get fusels and esters mixed up. Fusels taste more like rubbing alcohol, nail polish, etc and tend to kill head retention and cause head aches.
For the most part if you ferment under 72 with most ale strains you will minimize ester development.
All I can say is that’s the opposite of my experience.
I could come up with a plausible hypothesis for the first statement. Minimal ester production is occurring during the log growth phase, and increasing the metabolic rate could yield a little higher cell count and therefore lower esters.
The second part I don’t understand. I guess if there are a lot of fusels you’d accelerate the redox reaction (I can never remember which way it goes) converting them to esters, but that seems oddly specific.
But it’s still going to vary fr strain to strain. For instance, wy1056 will generate very little esters even as high as 72-74 degrees while a hefe wiezen strain will through all kinds of esters at 62. Increasing pressure on Some strains lowers the ester profile significantly. Pitching rates affect ester profile a heck of a lot (I’ve seen some studies that shows under pitching decreases esters with many strains over over pitching increases esters).
Regardless, pitching cool is going to reduce the amount of fusels and those you definitely want to keep as low as possible. Pitch and start out cool and you will have a cleaner tasting beer. As long as you stick to a decent pitching rate and don’t go crazy with the temp your ester profile will fall nicely into place. You may want to experiential with different temps, aeration times and pitching rates to find the profile you are looking for.