[beerstache]

I'm going to be using a batch of recently washed yeast and have some concerns about contamination.  I followed strict sanitizing methods to insure no contamination, but how can you be sure?  I hate to ruin a batch with bad yeast!
The starter smells good, like fresh yeast so that's good.  What's your experience with using washed yeast?  Any problems?
Thanks for your comments.

[Hokerer]

As long as you're reasonably careful about your sanitation, you'll be fine.  It's not like your beers are being infected, are they?  If you're yeast cake is infected, your brews would be too.

[tygo]

As long as you're reasonably careful about your sanitation, you'll be fine.  It's not like your beers are being infected, are they?  If you're yeast cake is infected, your brews would be too.

+1.  And if it smells good it probably is good.

[euge]

Your yeast probably has bacteria competing along side it in minute numbers. But given time they can grow if they have food. If the beer goes bad you'll know- but to be sure you need a microscope.

[tschmidlin]

Your yeast probably has bacteria competing along side it in minute numbers. But given time they can grow if they have food. If the beer goes bad you'll know- but to be sure you need a microscope.

I really think the value of a microscope is overstated for most homebrewers.  A very (very) small amount of bacteria can ruin a batch, and can be incredibly hard to find in a sample on a slide.  Without staining or selective plates, it can get lost.

[wildknight]

What's your experience with using washed yeast?  Any problems?

My experience is that it produces great beer and saves me money.  However, I follow a fairly rigid aseptic technique.  I autoclave bottles and flasks at work, and if I need something on short notice I use boiling water to sanitize before using.  I work over a strong flame (torch flame) to create an area of uplifting air where bacteria cannot settle.  My washing water has been autoclaved or at least boiled for 15 minutes, then cooled to the same temperature as the yeast before I wash it.  The area where I work is clean and I have sprayed 70% ethanol over the area.  Caps, threads, bottles tops - everything gets hit with ethanol before I transfer. 

Sometimes I just leave the yeast cake in beer and don't worry about washing it.  It is a lot less work and there aren't as many opportunities to contaminate it.  I find that yeast stored in beer stays viable longer than yeast washed 3-4 times then stored away.  I believe this is due to introducing oxygen at multiple times and getting the yeast starting to wake up over and over.  If you transfer from the carboy into a jar and put it in the fridge, then the yeast stay dormant and happy.

[davidgzach]

What's your experience with using washed yeast?  Any problems?

My experience is that it produces great beer and saves me money.  However, I follow a fairly rigid aseptic technique.  I autoclave bottles and flasks at work, and if I need something on short notice I use boiling water to sanitize before using.  I work over a strong flame (torch flame) to create an area of uplifting air where bacteria cannot settle.  My washing water has been autoclaved or at least boiled for 15 minutes, then cooled to the same temperature as the yeast before I wash it.  The area where I work is clean and I have sprayed 70% ethanol over the area.  Caps, threads, bottles tops - everything gets hit with ethanol before I transfer. 

Sometimes I just leave the yeast cake in beer and don't worry about washing it.  It is a lot less work and there aren't as many opportunities to contaminate it.  I find that yeast stored in beer stays viable longer than yeast washed 3-4 times then stored away.  I believe this is due to introducing oxygen at multiple times and getting the yeast starting to wake up over and over.  If you transfer from the carboy into a jar and put it in the fridge, then the yeast stay dormant and happy.

Wow, that is definitely a process!  Mine is not as thorough but have not bought yeast this year, and have made good beer, so pretty happy with the results.  I think just like brewing, as long as you are careful and have a sanitized process, you should be fine.

On the worry about it being bad.  If it was bad, one smell would tell you.  If the starter smells healthy, IMHO you are good to go!

[ynotbrusum]

You can also use a water purifying tablet to wash the yeast and kill most of the bacteria present.  I have never done that personally, but it is referenced in some peoples' processes.

[wildknight]

You can also use a water purifying tablet to wash the yeast and kill most of the bacteria present.  I have never done that personally, but it is referenced in some peoples' processes.

Are you referring to Campden tablets (sodium metabisulfite)?  These are used to kill bacteria and wild yeast.  In wine and cider making these are used to completely halt fermentation even with Sacc.  I have never tried using Campden in my starter to wash them, as it seems counterproductive to use a compound that kills yeast to purify your yeast and eventually make a starter. 

If someone has more experience with this, then I would be interested in hearing your experiences.