[mchrispen]

Opened my split batch of saison that has been on raspberries for a few weeks and found this:





At least this is in a Saison and more or less appropriate - it's pulling back in some esters that were buried under the raspberry flavor. Nice and tart!


I think I have found and eliminated the source of the contamination. I have to be MUCH better at sanitizing my yeast washing and storage jars.

[S. cerevisiae]

Your experience is a clear-cut reason why rinsing yeast with boiled water is a poor practice.  The process is flawed.  It is better to just crop and re-pitch.  Rinsing yeast with boiled water does not extend a culture's viability that much longer than leaving its low-pH, ethanol laden natural ecosystem intact, and a culture's natural ecosystem is significantly more resistant to infection from outside sources than boiled tap water, which usually has an alkaline pH with enough alkalinity buffer the pH of the culture above 5.

[mabrungard]

What if the water is acid-treated to bring its pH down to an appropriately low, yeast washing pH?

[klickitat jim]

Your experience is a clear-cut reason why rinsing yeast with boiled water is a poor practice.  The process is flawed.  It is better to just crop and re-pitch.  Rinsing yeast with boiled water does not extend a culture's viability that much longer than leaving its low-pH, ethanol laden natural ecosystem intact, and a culture's natural ecosystem is significantly more resistant to infection from outside sources than boiled tap water, which usually has an alkaline pH with enough alkalinity buffer the pH of the culture above 5.<br/>

Im really beginning to buy into this. Plus its easier and practical

[mchrispen]

I have to admit I was cheaping out and pushed the pitch to the 4th generation. Usually only pitch twice and discard. I pushed this saison yeast because its character was changing pitch over pitch.


I am more interested in making sure that I am conducting reasonably good sanitation. I share a series of mason jars to rotate yeast cakes (or washes). So I am convinced that the source was either a contaminated slurry (most likely), poor handling (treating all surfaces, implements and hands properly), or pure crap luck (also likely, if you knew me better you would understand).


As for the washing criterion - titrating low alkaline water (RO/DI) to around 4.2 or so works better? I have always boiled water to remove chlorine and "sanitize" - but would happily acid wash to facilitate. AND just treat this process with a lot more care.

[morticaixavier]

I just put however much of the cake as will fit into a sanitized quart mason jar and pop it in the fridge. works fine. Just pitched one of these that was a year old and it worked better than the original pitch of that culture. course, that was a mixed culture so it was already horribly infected 

[troybinso]

Isn't it possible that the source of contamination is the raspberries and not the yeast? If this is a split batch, did both parts get contaminated?

[S. cerevisiae]

What if the water is acid-treated to bring its pH down to an appropriately low, yeast washing pH?

If one is going to rinse with boiled water, lowing the pH of the rinsing and storage water to around 4.2 is a good start.  However, in practice, rinsing is a completely unnecessary step that has the potential to do more harm than good.

Brewers are told that they do not have to worry about pathogens because pathogens do not grow in beer.  The reason why pathogens do not grow in beer is because the pH of beer is below the minimum growth pH for pathogens such as Clostridium botulinum, which requires a pH of at least 4.8 in order to grow.

A yeast culture "owns" a batch of wort by shutting out competitors.  It rapidly consumes dissolved oxygen, which shuts out aerobic microorganisms.  A yeast culture also lowers the pH of the medium from around 5.2 to around 4.2, which shuts out pH sensitive anaerobic microflora.  The final defense that a yeast culture mounts is the production of ethanol, which is toxic to microorganisms, including the culture itself. 

Replacing green beer with boiled water strips the culture of the force field that it built for itself, which means that the water has to be completely free of wild vegetative cells (and spores that can germinate into vegetative cells) because they will feast on dead yeast cells.   Bacteria cells multiply three times faster than yeast cells, which means that a small infection can overtake a larger yeast culture when pitched into fresh wort.

[klickitat jim]

That's it, no more rinsing/washing for me. After racking to the keg, im leaving a half inch of beer, swirling, and filling a sanitized 1/2 gallon mason jar. Pop it in the fridge and use within a month. Easy peasy

[Thirsty_Monk]

That's it, no more rinsing/washing for me. After racking to the keg, im leaving a half inch of beer, swirling, and filling a sanitized 1/2 gallon mason jar. Pop it in the fridge and use within a month. Easy peasy

Now we are talking.
Just flame the mouth if the carboy. (Or sanitize the bottom port of conical).

[klickitat jim]

30L speidels, so ill just unscrew the bottom port.

[mchrispen]

Isn't it possible that the source of contamination is the raspberries and not the yeast? If this is a split batch, did both parts get contaminated?

Of course that is possible. I could pull some of the other beer and let it rest at room temp for a few weeks to see if it forms a pellicle. That half went into a first use whiskey barrel - and didn't develop any visible signs of infection. It is carbed and on tap right now.

The reason I believe the lab gear is the source, is that I had a second unrelated batch, in my stainless conical also develop an identical looking pellicle. Because that conical gets a more extreme sanitation regiment, the common denominator is lab gear, and any transfer hoses post boil. I proofed the yeast for that in a mason jar from my lab. So - everything in the lab, mason jars, erlinmyers, etc. has been heavily steamed and sanitized in the hope that that I nipped it.

As I mentioned, that was the 4th generation pitch of a Belle Saison yeast cake - really upping the odds of infection. In shifting to the Speidel fermenters, as opposed to carboys, I remember trying to figure out how to get that cake out of a giant 15 gallon fermenter. Couldn't reach the bottom inside, so poured the slurry through the spout at the bottom. I have dumped all of my yeast stores now, and resetting with a more rigid sanitation regimen. Will skip the washing as well.

[santoch]

One other possibility is to rinse the yeast with BMC, which as  we all know, is sex in a canoe.

[Multifaceted]

Bob Ross taught that there are no mistakes, only happy accidents.