Harvesting yeast question

So I was just watching a YouTube video on how to harvest yeast and saw these guys do something I would like to get feedback on.

They racked their beer into secondary like normal. Then they poured their brand new cooled wort for the next batch right onto the yeast cake, trub and all. I have never heard of this so am hoping to get all of your thoughts. This could save a ton of time and money.

Yep, it's actually quite common and can be done with beers brewed of similar style and characteristics. For example, I might be fine with brewing a nice pale ale with WLP001 and then using that trub on an IPA, and then turning around and using that same trub on a hoppy barleywine. As long as the styles compliment and the adjuncts that wind up in the trub don't clash with the new style being pitched on it, go for it.

There are no sanitizing issues?

Not really, seeing as most bugs don't survive well in an alcoholic environment. A batch of beer is kind of like a huge yeast starter anyway, so re-using the yeast before it starts to stress and produce tiny mutants is just fine. Use a sanitized racking cane to remove the beer each time off of the trub and you should be able to pour newly cooled and oxygenated wort directly onto it with no issues.

What usually is an issue are adjuncts that wind up in the trub. Mainly, hops. That's why starting with a nice light style such as a pilsner, a light ale or a wit might be a better choice, with the hops levels increasing as you keep brewing. You certainly don't want to attempt a cream ale over the trub that's been used on an imperial IPA, just too many hops wind up in the trub from a beer like that. So, start with lighter styles and go to more bitter/darker or just re-pitch the same styles on the yeast for four or five batches until the yeast start mutating.

Alright last question as you seem to know your crap. If I don't want to brew that same day can I transfer all of the trub and yeast into a clean growler and just dump it in my fermenter next brew day?

If it were going to be the next day or two, just leave it in the bucket or carboy with the lid and airlock in place. More than that, I would "wash" the yeast.

If you want to save it for a longer period of time, check the yeast washing sticky. It's very simple, and just requires a couple or mason jars and lids.

I got a side question, when you guys harvest yeast do you always make starters with the harvested yeast or can I just put the harvested yeast directly into the cooled wort given there are enough yeast cells?

I have always made a starter but is it really necessary?

You may want to read this before you pitch onto your yeast cake:
https://www.homebrewtalk.com/f163/why-not-pitch-your-yeast-cake-166221/

purphumpbackedwhale said:

I got a side question, when you guys harvest yeast do you always make starters with the harvested yeast or can I just put the harvested yeast directly into the cooled wort given there are enough yeast cells?

I have always made a starter but is it really necessary?

Click to expand...

It's impossible to generalize the answer when it really depends. What it mostly depends on are time and storage conditions. With a short time in the proper storage, no starter should be needed because nearly all the yeast would be viable. With time, more yeast cells will die and then you need to increase the good ones by making a starter.

Yes you can pitch straight onto a cake. However, understand that you are over-pitching. Since the cake has almost all the yeast required to ferment the next beer (some will have died), you will get little new yeast. It is the yeast reproduction that creates much of the precursors of the yeast flavors, so your beer will be low in yeast esters. You will also be brewing your beer with mostly old yeast; it may not be measurable, but you might not attenuate as much as you would when using a correct pitch amount.

I believe you will get a better beer if you only use about a quarter of the cake. The yeast are healthy, and it is still a sizable pitch so you will still get a quick start, but I think you will get a lot more benefit from it.

Dutch218 said:

Alright last question as you seem to know your crap. If I don't want to brew that same day can I transfer all of the trub and yeast into a clean growler and just dump it in my fermenter next brew day?

Click to expand...

My cakes are always close to 4 pints. After racking the beer off the cake, I swirl up the fermenter (usually don't need to add water, but occasionally do need a little) to get a slurry, then pour the beer into 4 sanitized pint mason jars. Then store in the fridge.

These days I wash the yeast before using, but for a long time I would just straight pitch a pint jar of the slurry for the next brew. My rule was if it was less than a month old, I would straight pitch, over that I would make a starter. Never had a problem; I even broke my rule by straight pitch jars at 3 months old on occasion (I cringe at the thought now, but I didn't have any problems).

I hope this answers some of your questions.

Warning: slurry when stored will create pressure, so you will need to vent any container every few days to release the pressure.