Why do people boil water to steralize for yeast washing?

I am starting to wash yeast and I noticed a lot of people boil the water before dumping it into the fermenter. Why is this necessary? In the cases of partial boils, tap water is poured directly into a fermenter - under the assumption that tap water is clean.

By the same extension, wouldn't tap water poured into a sanitized vessel be suitable for yeast washing?

Part 2 - From the attached picture - what level would you guys pour off into mason jars? This was from a kolsh I brewed, and it looks like 90% of what settled is trub and not yeast? This is my first time doing it.

Chances are your tap water is loaded with chlorine. You would boil it to remove some of that (at least), or filter it, or hit it with campden tablets to remove it. I won't drink/cook with tap water from pretty much anywhere on a city water supply (unless they have really good filters installed before the faucets).

For pouring off, I'd cold crash that jar for a day or three, so it gets more compact. Then decant most of the liquid off the top before breaking it down into smaller jars. Depending on how it settles, you could get a good definition of what's yeast and what's not.

For yeast rinsing you want to boil your water for a few minutes to kill anything that may be in it that could infect your stored yeast. My guess on pouring tap water directly into a fermenter would be that you are creating alcohol so that is not a very good environment for bacteria to grow as opposed to storing dormant yeast in a jar. As for the yeast in the pic, i would decant the liquid and pour clean boiled, then cooled, water to the jar. Shake the jar until everything is in suspension, let the jar sit for about 10 minutes or until the trub starts to separate and settle on the bottom, then pour out the yeast still in suspension leaving the trub behind and that should give you a clean yeast ready for your next batch or starter.

Ok, the water which I used for this was boiled first - I guess I wondered if it was absolutely necessary for all steps in brewing. I would think it will continue to be fine when a proof my dry yeast in water before adding it to wort.

I just moved the jug into my cool porch, and will decant it in a day or so. Why are you suggesting I add more clean water to it?

I was under the impression that you boil it to remove the oxygen so the yeast will be dormant in storage.

Britinusa said:

I was under the impression that you boil it to remove the oxygen so the yeast will be dormant in storage.

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It's not so much that, as you'd really like to be as sanitary as possible. I even boil my jars that I'm using to store the washed yeast in, to minimize bacteria and wild yeast.

It's not possible to be sterile, but I try to be as close to that as possible when I'm storing yeast.

Good answers above, i have 1 extra tip, when boiling water for washing i prepare several jars at the same time, then i "can" them with hot water and keep till ready for washing, its nice to have it ready, sterile and cool

LateraLex said:

Why are you suggesting I add more clean water to it?

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The main reason you should add more water is because it makes it easier to separate the yeast from the junk you want to leave behind. If you try to separate with equal parts water to yeast/trub the mixture will be too thick and you will end up carrying over more of the stuff you don't want.

I'm actually now somehow more confused than when I started. Here's what I've gathered:

• Cold crash the mason jar to compact the yeast cake
• Drain off the clear liquid
• Maybe: add additional clean water to the jar?
• Shake up the jar, and pour into small jars

Not sure how/when I'll be able to get rid of the sizable chunk of trub at the bottom, if the yeast needs to be in suspension in order to pour it off?

One tip I have found is that once you add your water to the fermenter you need to let it setting for 20 minutes before pouring into jars, this way the yeast slurry is the only thing poured off into jars and 90% of the heavy trub gets left in the fermenter.

After the first jar pour I always decant one more time into smaller jars so that I end up with about 1/3 cup of settled yeast per jar which just happens to be about 100 billion yeast cells, perfect for a starter!

LateraLex said:

I'm actually now somehow more confused than when I started. Here's what I've gathered:

• Cold crash the mason jar to compact the yeast cake
• Drain off the clear liquid
• Maybe: add additional clean water to the jar?
• Shake up the jar, and pour into small jars

Not sure how/when I'll be able to get rid of the sizable chunk of trub at the bottom, if the yeast needs to be in suspension in order to pour it off?

Click to expand...

You might want to check out 'Woodlandbrew' blogsite. This guy has done some studies on yeast washing and yeast viability that has me rethinking my standard washing technique.

LateraLex said:

I'm actually now somehow more confused than when I started. Here's what I've gathered:

• Cold crash the mason jar to compact the yeast cake
• Drain off the clear liquid
• Maybe: add additional clean water to the jar?
• Shake up the jar, and pour into small jars

Not sure how/when I'll be able to get rid of the sizable chunk of trub at the bottom, if the yeast needs to be in suspension in order to pour it off?

Click to expand...

When you harvest the yeast and first put it in a jar you DO NOT want to cold crash and compress the yeast. Just put the jar in the fridge for 10 or 15 minutes. The trub will start to settle out right away while the yeast stays in suspension. After the trub has settled out, pour the liquid off into a sterilized jar. Now you have separated the yeast from the trub and can begin the other steps.

Ah that makes sense. What I really need to do is to shake the hell out that jar, and pour off the top layer it into another container after a few minutes.