Wednesday, October 20, 2010

Yeast hunting: update

The yeast cultures from the Stonington, Connecticut vineyard hunting trip have all burst to life with some very interesting and encouraging results.

While I was sitting around waiting for things to happen inside those tubes, I found lots of practical and timely reading through Jamil's (just as much Chris White's) yeast book. Had me harkening back about 15 years to my Microbiology 101 class with all of this aseptic technique, plating agar media, incubators talk.

Now, I'm not going to venture off in to selective media, vitality or viability testing or anything too geeky, but rather rely on sensory evaluations and macroscopic techniques.

The first macroscopic observations actually came the evening of the collection, only about 10 or so hours after the cultures were started. I noticed turbidity and some positive pressure on one of the tubes with the Sauvignon Blanc grapes...a little agitation revealed some CO2 production. Interestingly, these are the first grapes to ripen and were harvested a few weeks prior to our visit. There were a few straggler tiny clusters missed by the harvesters, so I was able to snag a few for my effort.

Anyway, I guess I wasn't going to have to sit and stare at these for days on end before at least 1 tube with some growth. A sniff along the cap didn't yield much, so I re-tightened the lids and turned the tubes over on to their caps for the night. The centrifuge tube cone bottoms require a rack, and the cardboard rack would take too much of valuable counter space. I tucked the 11 tubes in to small corner of my cutting board, and went to bed for the night.

Agitated them all again in the AM before shooting out the door in a futile attempt to miss the Monday AM Boston traffic. Came home that evening to see 2 or 3 of them leaking fairly significant amounts of wort (beer?) from the screw threads, mabye as much as 1/3 of their total volume, due to the built up CO2 pressure. Well...duh.

Good news is that the headspace in the tubes was filled with CO2...bad news is that I probably lost lots of viable bacteria and yeast in those, most noticeably in that tube of Sauv. Blanc, which when agitated put forth even more frothy CO2 bubbling, and this time a vinous, white winey lactic and bread yeasty smell.

The open air tube had some strange brown coagulated proteins, which reminded me a lot of the first stages of culturing up the kombucha bugs. No CO2, though. Maybe the clumps are hot/cold break from the DME? All the tubes w/ the white grapes were showing signs of life, while the reds were pretty silent. Oddly, all the tubes with grapes were seemingly devoid of these brown coagulated clumps.

Three days after harvest, all the white grapes were still actively fermenting, and yeast seemed to be floc'ing in the bottom of the tubes in stratified layers. The reds were quickly following suit, just a bit behind the whites. No CO2 production evident from the open air vial, just the brown clumps. Are the brown clumps growing?...maybe a bit more turbid now? (should have take photos in same position/lighting for side by side comparison).

The next step was the following weekend (Day +7) when I took 1 tube of each of the four grape varietals, agitated to get the yeast/bacteria cakes in to suspension (had to shake pretty hard for some of the tubes) and pitched in to ~250ml of starter wort + pinch of nutrient. There was significant turbidity and CO2 production and some leaking at most of the tubes' cap threads.
The Sauv Blanc tube that was the most active from day 1 was very turbid at this point, and and took the blue ribbon yeast production, despite the reduced propagation media volume.
I sniffed each of the vials (too nervous to taste anything yet).
All but the merlot smelled like raw, yeasty fermenting wine. The merlot smelled like raw sewage on a hot summer's day. But just a small tube of it, so thankfully a minimal nostril full didn't leave me reeling, spilling the vile stink all over the kitchen. Guess I got a bloom of Enterobacter? Glad I didn't taste it. It got pitched in to its fair share of starter wort, hoping that the more benevolent creatures start to outcompete this stink stank stunk bacteria. The cultures were topped with foil and rubber bands (to minimize any stank spilling, should one get tipped in the high traffic kitchen) and were swirled to agitate whenever I walked by.
Fast forward one day, and little creamy white growths appeared on all of the cultures. Certainly didn't have the morphology of a mold bloom, most resembled what in my experience looks like yeast (mini) krausen.
The next day I took the 2nd runnings from a batch of belgian strong (gravity read at 1.034) and topped up the cultures with another 250ml of wort.
Fermentation was evident in the AM, with CO2 emerging through the media. These were left to ferment for 5 more days (Day +13) and sufficient yeast was settling at each of the cultures and continued to be very turbid. I've read that lots of wild yeasts can be very dusty, but its not really possible to know whether this was due to dusty yeast or otherwise high and varied bacterial blooms. I chilled the samples down in the fridge in an attempt to crash the yeast out of suspension, in order to repitch a hopefully concentrated yeast cell count in to more starter wort. Uncapping the foil revealed a very similar looking pellicle in each.
Again, certainly no mold, but the aroma profiles have begun to differentiate themselves.
  • Sauv Blanc smelled strongly of fruity kombucha (indicating some acetobacter produced acetic acid)
  • Chardonnay was a softer kombucha/acetic, more raw and yeasty
  • Cab Franc was notably vinous with a smaller, softer background odor of bready yeast
  • I took a very short sniff of the Merlot fearing the worst, but it seems that my hopes were realized...the Enteric poop stink has been mitigated significantly, and is now just a faint background odor. Perhaps just remnant volatile odor compounds from the now outcompeted bacterial population.
The cultures were decanted and added to ~225ml of wort, affixed with an airlock, and now currently sit at room temperature. I neglected to take any gravity readings.

Single tubes of each varietal + the open air tube remained, and signs of fermentation continue on the tubes with grapes. Its like the microbes are slowly gaining access to the sugars/nutrient in the grapes so are slowly chewing away. The color change in the red cultures is obvious. No obvious pellicle forming like in the foil covered larger cultures.
As for the open air tube, we finally have significant CO2 production, first noted at Day +11. You can see the foam leaked around the threads after agitation...smelled raw vinous, yeasty (sorry for the repetitive descriptors...I'll employ far more colorful vocabulary when I act like a man with actual hair on his chest and take a swig).
Stay tuned for the next exhilarating microbiological installment when I actually make something intended for at least a small taste analysis.

Plans call for making a small batch of a relatively lightly hopped farmhouse style beer, splitting the wort across 4 ~ 1 gallon fermenters and see what kind of primordial beers we end up with on their first generations. I'll grow up the additional 5 samples behind these first 4 to see if there are any significantly different characteristics, and selecting a few that smell the most benevolent. There are also plans for streak out the mixed cultures on some malt agar media, isolate some yeast from the bacteria, then slowly step up in 25, 50, 100, 250, 1000ml erlenmyers to grow up pure cultures to more split wort 1 gallon pitching volumes, but that'll be a story for a future post.


  1. Looking great. It looks like you might have a large mix of yeasts and bugs. I am surprised by the variation that you already see in the smell of the starters. It appears that it is a good choice to take as many small samples as possible to start with and then you can be a bit more selective as they progress.

    It also looks like you made a pretty decent investment in new lab equipment. Could you share what you got and where? And rough costs? The holidays are coming up and this might make it to the top of my list.

  2. i was happy to get anything remotely 'good' at all, to be honest. I am looking at this as a great way to dip my toe in to (re) learning handling microbes beyond the commercial pure cultures, and even with this modest number of samples, without a dedicated space, it can get pretty laborious and requires a ton of individual vessels, if I were to grow up each to even the 1 gallon test batch.

    and yes,I am quite happy to find the variability in bugs within this tight microclimate.

    more details on the lab set up coming in a future post!

  3. This is very cool, and more than a little inspiring. Nice job!

  4. waaaay too much fun. nice stuff dude, keep it up.


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