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Lucas
10/22/08 10:19 AM  
ginger experiment
Hi all, I have a great experiment going on and I'd love to hear what you think of it. Basically, I read that a lacto- and alcohol-fermented drink called 'jamaican ginger beer' was traditionally made by cultivating the microorganisms living on the surface of fresh ginger root. I've never thought there was anything magically special about store bought yeast so my experiment is to try isolating a usable fermenting culture, while minimizing lactobacillus and other bacteria. I set up a 1gal carboy with a normal generic beer wort (extra hops to mess with lactobacillus, malt extract) and a bunch of finely chopped ginger. i put on an airlock and timed the bubbles at frequent intervals. +2 days after inoculation, positive pressure indicating yeast activity

+3 days, reaches peak CO2 production, after which bubbling slowed down constantly to almost zero, then leveled off.

+10 days, much to my surprise, CO2 activity started increasing again

+12 days, reaches ANOTHER peak CO2 production, even faster than the first!

thats pretty much as far as i've gotten so far.

further observations:

the 1st fermentation smelled what i can only describe as sketchy. a large, healthy krausen developed, of an overall dark green color.

the 2nd fermentation smelled amazingly fruity. also had a healthy krausen but much lighter in color, started off white and ended light green.

so after all that, the reason i wrote this post!

1) what is going on? does someone straight-up know?

2) do you think the first fermentation bubble was caused by a bunch of weird yeast species, while the second was primarily due to one alcohol tolerant species?

3) if so, do you think the alc. tolerant species is just S. cervisiae or something else?

4) does anyone know of a convenient way to try isolating the yeast causing the second ferm.? I tried just scraping some foam off and making a starter (hoping its a top-fermenter!)

alright, thats it! sorry this post is so long, i'm just excited!

David M
10/22/08 01:39 PM  
Re: ginger experiment
I'll leave the analysis to someone who is experienced with the yeast stuff, but I'm interested in the results of this. One thing to keep in mind is that you probably have a bunch of different yeast species that have attached themselves to the ginger through the process of harvesting, shipping, selling, etc.
Baums
10/22/08 04:12 PM  
Re: ginger experiment
Hey Lucas. I have a few comments:

There are ways to "know" what a bug is but they are extremely involved and require (at the least) a bunch of different media and lab equipment. Maybe some simpler experiments could narrow it down (looking at the cells through a microscope would be a start), or maybe you can bribe a grad student at a local college to help you. But in any case, the easy part is finding candidate bugs (on ginger, or cabbage, or scraped out of the gutter in Liege) and the hard part is identifying them.

BTW if you have a good college library near you, it can be interesting to look through early editions (before they started using a more genetic approach) of "The Yeasts: A Taxonomic Study." They provide a record of what leading microbiology researchers in the 20th century found when they set about isolating bugs from all sorts of things (cider presses, horse urine, topsoil, frogs, you name it), and how they classified things. It even explains the daunting series of experiments necessary to classify an unknown bug the way they would have.

I think that kind of science-based technical stuff is necessary if you want to talk in terms of "cerevisiae" and "lactobacillus." But if you just want a fun mystery culture to brew with, things are a whole lot easier and you're on the right track by mimicing various traditional methods. (BTW I am pretty sure pathogens can live just fine in wort, so I would just go around drinking anything you find, especially if it smells sketchy.) If it were me, I'd get some fresh organic fruit (say apples or grapes) and make a cider/wine type thing with the yeast on the skin, and then start repitching the dregs into small batches of beer, and see what happens.

Baums
10/22/08 04:13 PM  
Re: ginger experiment
Uh, I think I meant "I would NOT just go around drinking anything you find..."
Lucas
10/22/08 05:05 PM  
Re: ginger experiment
Thanks for your advice Baums, I certainly understand if some of my questions were unanswerable without advanced equipment. I also understand I'm meddling with crazy things and I might get burned. I'll be (semi-) careful!

perhaps I should specify some more conceptual questions:

-) Can a "double fermentation" like this be caused by a community of low alcohol-tolerance organisms being out-competed by a single strain? It seems like this might have happened to people trying other wild fermentation techniques.

-) Is there any way to gradually produce a culture consisting predominantly of the alcohol-resistant yeast?

For example, would harvesting yeast from the foam created by the desired yeast be superior to harvesting directly from the fermenting liquid? Also, would it be a good idea to create a wort, then mix in vodka or something to around 5% ABV before pitching the yeast culture? it seems like this might prevent some of the undesireable critters from gaining a foothold.

-) Is it better to do these kinds of manipulations in small quantities to allow a high concentration of initial yeast (like a quart) or give the organisms some room to breath (gallon)?

again, all knowledge and opinions greatly appreciated!

BPotts
10/22/08 09:44 PM  
Re: ginger experiment
I had a "double" fermentation when I used a blend of brett c & b for a barleywine. My theory is that one strain started out dominant but then pooped out and the second took over after the first stopped.
Baums
10/24/08 02:00 PM  
Re: ginger experiment
My brainstorms are similar to yours... grab the creamiest yeasty looking stuff, and pitch it into some already-alcoholic wort (though I think 2% would be better), wait for it to ferment. Repeat. Hope.
Lucas
10/28/08 09:38 AM  
Re: ginger experiment
Had progress in the experiment! after cultivating yeast collected from foam in low alcohol-content wort (~4-5%) I made a starter with the best stuff i had and stuck it in a gallon jug of generic beer wort. Put an airlock on it around noon yesterday, came back around 4 and it was bubbling, came back at around 11pm and it was fermenting so furiously that foam was exploding through the airlock. It eventually clogged the hole in the cork and pressure built up. Seeking not to destroy anything in my house, I removed the cork and airlock (spewing mystery yeast everywhere). It was foaming so fast at this point that there was a constant stream of foam exiting the jug. I left the cork off and went to bed. Woke up this morning and fermentation had slowed down, but here's the awesome part: the foam slowly escaping had solidified into a crazy foam flower extruding from the jug. in other words, my yeast can make its own airlock! Just thought people might find that neat.

I'll let the jug ferment to completion, then bottle and test!

 
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