Author Topic: Wild Yeast Revisited  (Read 1989 times)

Offline Kevin B

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Wild Yeast Revisited
« on: July 04, 2015, 01:41:41 AM »
Hi All, new to the forum! I've been homebrewing for about 6 years now (mainly all-grain ales and meads) and had a question about cultivating wild yeast - but it needs a little backstory first... (sorry in advance if it's a little verbose...)

Spring 2013, I was working on a horse farm near where I live, when I noticed a maple tree that had foam coming out of a damaged area in it's bark about 6 feet off the ground  :o my first thought? WILD YEAST!  Me being a lover of Lambics, I talked to my boss who knew I was a homebrewer (and had enjoyed me brews many a time), and they agreed to let me come back on my day off and collect some samples.  I collected samples of the foam on sterilized plastic spoons then dropped them directly into sterilized 1 gal. glass jugs containing a mixture of boiled sugar water and yeast nutrients.  Here's what happened over the next couple days...

0 hours -


24-36 hours -


72 hours -



I was amazed! Not only did they take right off and ferment, but the fermentation smelled "clean" - slightly tart, but no major off-aromas that would indicate something really funky going on.  Even after primary fermentation, it didn't even form a pellicle like I've heard wild yeasts/bacteria cultures do. I realized that by some stroke of wild luck I had a winner on my hands!  But then... life got in the way.  Due to circumstances I had to move from my current home, and soon after that I stopped working at the farm (my boss and I kinda had a falling out...) so this culture was all I had... During the chaos that is packing, I had packed a washed and stored sample of this clean wild yeast culture with the intentions of using it as quickly as possible - but it became forgotten in a back corner of the basement, stored at my folks place during the move...

Fast forward to about a week ago...

After going through some crates in the basement I came across the bottle of washed yeast culture that was a year and a half old.  I remembered how well it did, and instantly lamented the fact that I had not used it sooner.  Still, who knows - there might be some cells that might still be alive but dormant in the cake in the bottom of that bottle... So this past Wednesday I mixed up a batch of DME with yeast nutrient, shook up the bottle and poured about a quart of the yeast slurry into a gallon of starter. (As a side note, when I opened the bottle containing the old yeast slurry it smelled and tasted of lemons and tart green apple, it reminded me somewhat of Lindemans Cuvee Rene - I coulda' kick myself at letting such a find go to waste!)  2 days later (today) I noticed that the airlock on the bucket had started to rise, indicating fermentation, and I was overjoyed!  Some of the yeast had survived!  So I cracked the bucket to hazard a look...



What the hell?!?!? I got a whiff of creamed corn then I saw a 1/2 inch thick mass of goo... I was looking at a pellicle - a pellicle never formed on the initial culture, so why was there one now? Was it because there were so few live yeast cells that the bacteria in the mix took over? No matter the reason, I now have a new challenge - separating the yeast from the floating mass of khaki colored jelly :P  Not a total failure, but definitely a setback...

I looked online for info about culturing wild yeasts, but most sources usually state something to the effect of "separate the yeast from the pellicle" but never detail the actual process and go straight to creating agar plates to isolate a clean culture...

So my question... Since I have a pellicle and active fermentation, does anyone know what the actual process of separating yeast from a pellicle is?

**edit: I just read S. cerevisiae's post "Just say "no" to yeast rinsing" and now I'm kicking myself a second time for rinsing the culture before I packed it - that's probably where all the bacteria to form a pellicle came from...
« Last Edit: July 04, 2015, 02:07:22 AM by Kevin B »

Offline klickitat jim

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Re: Wild Yeast Revisited
« Reply #1 on: July 04, 2015, 07:04:21 AM »
Beyond my level, but sounds like you'd have to plate it out and isolate the strain you're searching for. Which probably means several present strains and several separate test batches till you find it.

Offline pete b

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Re: Wild Yeast Revisited
« Reply #2 on: July 04, 2015, 11:32:57 AM »
I'm looking at a very small picture on my phone but I don't see pellicle. Pellicle usually has big bubbles and/or a white lace. I don't see that.
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Offline narvin

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Re: Wild Yeast Revisited
« Reply #3 on: July 04, 2015, 12:01:35 PM »
Yeah, that doesn't look like a pellicle.  A pellicle is a white film that wild yeast makes in the presence of oxygen.  What you have looks like bacteria and yeast forming a mat, like kombucha.
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Offline heavydeadlifts

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Re: Wild Yeast Revisited
« Reply #4 on: July 04, 2015, 01:38:30 PM »
That is krausen from fermenting yeast

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Offline bboy9000

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Re: Wild Yeast Revisited
« Reply #5 on: July 04, 2015, 02:41:40 PM »
Looks like krausen to me too.
Brian
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Re: Wild Yeast Revisited
« Reply #6 on: July 04, 2015, 03:31:36 PM »
If you want to isolate the wild bugs, you will need to plate the culture for "singles."  A plated culture will look like the one that I streaked in the photo shown below; however, your culture will have different colors and textures due to being a mixture of yeast, bacteria, and/or mold.



Additionally, many home brewers confuse sanitation with sterilization. In microbiology, the word sterile has a specific meaning; namely, devoid of life.  Soaking an item in a bleach, iodophor, or Star San solution results in the item being sanitized.  Sanitary means that most of the vegetative cells have been killed.  Boiling kills all of the vegetative cells, but it does not kill spores, which means that the item or liquid is not truly sterile.  The commonly accepted ways to sterilize an item are to subject the item to 121C/250F moist heat at 15 pounds per square inch above normal atmospheric pressure for 15 minutes (known as autoclaving), or dry sterilize the item with 177C/350F heat for 90 minutes. 

One should use a truly sterile collection device and propagation medium when attempting to capture and propagate wild microflora from a specific source.  That way, one knows that one captured the target strains, not residual domesticated microflora in one's house or wild microflora from other sources.   The easiest way to collect wild strains is to use individually packaged sterile cotton swabs and presterilized plastic culture tubes or transport tubes.  The head is snipped off using a pair of sterilized scissors (flame sterilization is the easiest) and dropped into autoclaved wort in the presence of a flame source (hot air rises therefore microflora, which rides on house dust, will not settle around a flame source).  One can be assured that the microflora came from the source if the wort starts.

By the way, Becton Dickenson makes a cool, integrated cotton swab and tube that is purpose designed for the collection of microflora.  It's called a SWUBE.

www.bd.com/ds/productCenter/220210.asp



The price for each tube is between $1.50 and $2.00, but they have to be purchased by the case. 
« Last Edit: July 04, 2015, 04:17:31 PM by S. cerevisiae »

Offline narvin

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Re: Wild Yeast Revisited
« Reply #7 on: July 04, 2015, 03:42:19 PM »
Looks like krausen to me too.

It looks kind of like krausen now but in my experience with wild fermentations as it continues to grow it forms a solid film that never goes away.
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S. cerevisiae

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Re: Wild Yeast Revisited
« Reply #8 on: July 04, 2015, 04:28:14 PM »
Looks like krausen to me too.

Wild yeast strains generally do not floc to the top like domesticated yeast strains. 

Offline brewinhard

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Re: Wild Yeast Revisited
« Reply #9 on: July 04, 2015, 11:06:13 PM »
+1 to looking like a classic yeast fermentation.  Looks like when a krausen starts falling back into the beer. 

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Re: Wild Yeast Revisited
« Reply #10 on: July 05, 2015, 05:20:37 AM »
+1 to looking like a classic yeast fermentation.  Looks like when a krausen starts falling back into the beer.

Except for the fact that wild yeast generally does not form a yeast head. 

Offline bboy9000

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Re: Wild Yeast Revisited
« Reply #11 on: July 05, 2015, 06:55:10 AM »

+1 to looking like a classic yeast fermentation.  Looks like when a krausen starts falling back into the beer.

Except for the fact that wild yeast generally does not form a yeast head.
Are you saying it isn't yeast at all or does the OP live downwind from a brewery?
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Offline narvin

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Re: Wild Yeast Revisited
« Reply #12 on: July 05, 2015, 12:26:50 PM »
I'm telling you guys... that "krausen" isn't gonna fall.
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Re: Wild Yeast Revisited
« Reply #13 on: July 05, 2015, 02:07:42 PM »
Are you saying it isn't yeast at all or does the OP live downwind from a brewery?


They only way to know what is in that culture is to plate it for singles.  If there is top-cropping yeast in the culture, then the OP's collection devices were contaminated with microflora from his brewery because the  probability of finding a top cropping strain in the wild, while not zero, is very very low.

One of the reasons why true top-croppers can be repitched so many times is due to the fact that wild yeast and bacteria are usually non-flocculent; hence, they remain in suspension long after the yeast has formed a dense skimmable head.  True top-cropping behavior is the result of domestication.  German chemist Max Emil Julius Delbrück duked it out with Dane life scientist Emil Christian Hansen for the hearts and minds of brewers during the early days of pure cultures.  Delbrück's "Natural Pure Culture" method of maintaining pure cultures was based on the fact that top-cropping naturally purifies a culture. Delbrück felt that his method was superior to Hansen's pure culture method because Hansen's method relied on aseptic handling of the culture, which Delbrück felt was impractical in a production brewery.  Hansen won the war because his technique worked equally well for all yeast strains.  Descendants of the yeast propagation system that Hansen and Søren Anton van der Aa Kühle designed at Carlsberg Laboratory are in use in breweries today. 
« Last Edit: July 05, 2015, 07:11:45 PM by S. cerevisiae »

Offline jeffy

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Re: Wild Yeast Revisited
« Reply #14 on: July 05, 2015, 05:51:15 PM »
Are you saying it isn't yeast at all or does the OP live downwind from a brewery?


They only way to know what is in that culture is to plate it for singles.  If there is top-cropping yeast in the culture, then the OP's collection devices were contaminated with microflora from his brewery because the The probability of finding a top cropping strain in the wild while not zero is very very low.

One of the reasons why true top-croppers can be repitched so many times is due to the fact that wild yeast and bacteria are usually non-flocculent; hence, they remain in suspension long after the yeast has formed a dense skimmable head.  True top-cropping behavior is the result of domestication.  The German chemist Max Emil Julius Delbrück duked it out with Dane life scientist Emil Christian Hansen for the hearts and minds of brewers during the early days of pure cultures.  Delbrück's "Natural Pure Culture" method of maintaining pure cultures was based on the fact that top-cropping naturally purifies a culture. Delbrück felt that his method was superior to Hansen's pure culture method because Hansen's method relied on aseptic handling of the culture, which Delbrück felt was impractical in a production brewery.  Hansen won the war because his technique worked equally well for all yeast strains.  Descendants of the yeast propagation system that Hansen and Søren Anton van der Aa Kühle designed at Carlsberg Laboratory are in use in breweries today.

Cool info.  I always thought Delbruck was only famous for lactobacillus.
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