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'''Wild yeast isolation''', sometimes known as "yeast wrangling" or more formally [https://en.wikipedia.org/wiki/Bioprospecting "bioprospecting"], refers to the process of catching wild yeast, and isolating it with agar plates as a pure culture. This article will also contain information on growing up a ''captured'' culture in wort rather than isolating yeast cultures on agar plates. Culturing wild yeast and bacteria should not be confused with [[Spontaneous Fermentation]] because many of the microbes that might make a flavor impact during spontaneous fermentation are killed off during the wild yeast culturing processes.
:''Special thanks goes out to Bryan from Sui Generis blog and Jeff Mello from Bootleg Biology for providing the information in this article.''
* [http://bootlegbiology.com/diy/capturing-yeast/ Bootleg Biology] defines three methods of catching a wild yeast.
* [http://suigenerisbrewing.blogspot.ca/2014/12/two-new-videos.html Sui Generis Blog] video tutorial for catching wild yeast from fruit or from the air.
* David Thornton of [[SouthYeast Labs]] describes his favorite method of catching wild yeast/bacteria: "Most of our cultures are taken from over-ripened fruit macerated in its own juice and left to ferment 24 hours at the location in a small erlynmeyer Erlenmeyer with a perforated cap. Always grows something, and almost always get an alcohol fermenting strain, and of the alcohol fermenting strains id say 10% are worth brewing with. I like this method because I can stir my loop and do a streak on regular UBA aerobically, then pull favorable looking colonies for yeast and ''Lactobacillus'' and do a quadrant streak on selective media for isolation." <ref name="Thornton">[https://www.facebook.com/groups/MilkTheFunk/permalink/1141930175835195/?comment_id=1142286619132884&reply_comment_id=1142394019122144&total_comments=4&comment_tracking=%7B%22tn%22%3A%22R6%22%7D Conversation with David Thornton on MTF. 09/06/2015.]</ref>* Monitor for mold growth. If mold begins to grow on the growth media, scrape it out and continue on with the isolation process. This should be safe since isolating the yeast will separate it from any potential mycotoxins that developed during the initial catching. Do not consume any growth media that has had mold grow on it (see [[Mold]]). One suggested method is to remove any materials (fruit, leaves, etc.) that were used as an inoculant as soon as visible fermentation happens; this can help avoid mold growth by removing floating material <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1812527172108822/?comment_id=1812566615438211&comment_tracking=%7B%22tn%22%3A%22R%22%7D Caroline Whallen Taggart on removing fruit to prevent mold. Milk The Funk Facebook group. 09/05/2017.]</ref>.
* In general, summer and spring are more successful times to catch wild yeast, however any time of year can be successful. Simply choose fruits or flowers that bloom/grow during that particular season. For example, in spring, flowers and fruit blossoms are a good source. In summer, wild summer fruit can be a good source (raspberries, strawberries, cherries, etc.). In the fall, apples and grapes can be a good source. In winter, juniper berries <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1683379841690223/?comment_id=1683799054981635&comment_tracking=%7B%22tn%22%3A%22R%22%7D Milk The Funk thread on the best seasons for bioprospecting. 05/11/2017.]</ref>.
* A new study showed that wild yeast actually exists more so in leaf matter on the ground than it does on bark or fruit. See the [[Wild_Yeast_Isolation#Videos|"Where (Do) the Wild Yeast Roam" video by Bryan from Sui Generis blog]] below.
* [https://www.facebook.com/groups/MilkTheFunk/permalink/1034954619866085/ David Thornton's use of foam as stoppers.]
* Bryan of [https://suigenerisbrewing.blogspot.com/ Sui Generis Blog] instructions for using a jar of wort and cheesecloth to catch microbes in the air:
<blockquote>
"1) Prepare wort with an OG of 1.040, with enough lactic acid added to reduce the pH to 4.5. I'll often split this off of a normal brew day, prior to my hop addition, or you can make it from DME/LME. I am usually filling a 1L wide-mouthed pickel jar with the wort. I fill the jar to just below the threads.
2) I place the jar, covered with sanitised cheesecloth, in a place where I want to collect <nowiki>[microbes]</nowiki> from - usually I aim for an area with either growing plants (garden, etc), or in an area with lots of deciduous trees, as I've had the best success in these areas. I put the jars out in the evening, once the afternoon heat has passed, and gather them the next morning. I don't worry about having the wort hot and letting it "cool" to mimic a cool-ship as I've found this to not matter. In fact, I often pre-can (using a pressure canner) a few of these, and take them with me camping or to the cottage, to gather the local yeasts. You could even "guerrilla capture" yeast by sneaking these jars into local orchards/farms/etc...not that I'd ever do that ;-)
3) After collecting the (hopefully inoculated) jars, I remove the cheesecloth and replace it with the jar's lid + an airlock fitted into a hole I've drilled. I then place the jar in a dark warm place and let it sit for 3-4 weeks before I sniff test it. If it smells OK I will typically brew with it within the next 2 weeks.
A few other pieces of advice:
1) This works best in the spring and fall - e.g. when nighttime temperatures are getting below ~10C/50F. When its warmer I've found my success rate drops from >80% to ~50%. This doesn't work well if the temperature is going below freezing, as the small volume of wort will inevitably freeze.
2) A small amount of "pure" alcohol can be added to improve your chances - e.g. add enough vodka or other unflavoured cheap booze (whiskey, unflavoured rum, etc) to bring your starters alcohol content up to 3-5%; this will suppress a lot of the unwanted <nowiki>[microbes]</nowiki>. For example, in my case I typically have ~900ml of wort in my 1L jar. To get 5% ABV I would make up 790 ml of wort (at ~1.045), to which I would add 110 ml of 40% ABV vodka. This will give ~5% alcohol, and keep the gravity above 1.035. Obviously, you add the alcohol after the wort has been boiled/canned/etc as you won't want to boil it off.
3) Hoped wort can be used as well, although my success at getting yeast + lacto with hopped wort is poor...I usually only get yeast, even with a meagre 3-5 IBU.
4) Raccoons, possums, rats, squirrels, deer, and pretty much every other fur-bearing animal (and some of the feather-bearing kinds as well) love unfermented wort, so try to place your jar somewhere they cannot get at it - while still maintaining airflow. We've got wild turkeys in the back, and those f***ers can fly (editor's note: language, Bryan!), so its a real challenge to keep them out." <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1817522898275916/?comment_id=1817911281570411&comment_tracking=%7B%22tn%22%3A%22R1%22%7D Bryan of Sui Generis blog. Milk The Funk Facebook group post on catching wild yeast. 09/10/2017.]</ref>
</blockquote>
===Isolating===
* The addition of hops in the starter wort will inhibit or kill some gram positive bacteria pathogens (''L. monocytogenes'' and ''S. aureus'') <ref name="Menz1">[http://www.ncbi.nlm.nih.gov/pubmed/22004814 Growth and survival of foodborne pathogens in beer. Menz G., Aldred P, Vriesekoop F . Oct 2011.]</ref><ref name="BryanMTF">[https://www.facebook.com/groups/MilkTheFunk/permalink/1104757552885791/?comment_id=1105118642849682&offset=0&total_comments=15&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Bryan of Sui Generis Blog on MTF regarding when it is safe to taste wild beer. 7/6/2015.]</ref>.
* A low pH is not the only requirement for making beer safe. A combination of alcohol, low pH, and hops will ensure that pathogens cannot grow (survival is another matter) <ref name="Bryan">[http://suigenerisbrewing.blogspot.ca/2014/02/fact-or-fiction-can-pathogens-survive.html ''Fact or Fiction? Can Pathogens Survive in Beer?'' Sui Generis Blog.]</ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/20207437 The growth and survival of food-borne pathogens in sweet and fermenting brewers' wort. Menz G1, Vriesekoop F, Zarei M, Zhu B, Aldred P. May 2010.]</ref>.
* Two studies have shown that ''E. coli'' can survive in moderate strength beer (~5% ABV, 4.3 pH) for at least 28 days (more than 30 days in one study) if the beer is stored cold (39-41°F or 4-5°C) <ref name="Menz1"></ref><ref>[http://www.ncbi.nlm.nih.gov/pubmed/24674433 Survival of foodborne pathogenic bacteria (Bacillus cereus, Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Listeria monocytogenes) and Bacillus cereus spores in fermented alcoholic beverages (beer and refined rice wine). Kim SA1, Kim NH, Lee SH, Hwang IG, Rhee MS. March 2014.]</ref>. Therefore, the wild culture should be stored at room temperature for a least a month before tasting. '''Additionally, the pH of the beer should be less than 4.6, and alcohol should be present for at least one month before tasting. The smell of feces or vomit indicates that bad bacteria may be present; if so dump it out ''' <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1104757552885791/?comment_id=1104851526209727&offset=0&total_comments=8&comment_tracking=%7B%22tn%22%3A%22R1%22%7D Conversation with Bryan of Sui Generis Blog on MTF regarding when it is safe to taste wild beer. 7/5/2015.]</ref>.
* In unfermented wort, ''E. coli O157:H7'' and ''Salmonella typhimurium'' were shown to grow at a pH of 4.3, but stopped growing at a pH of 4.0 <ref name="Menz1"></ref>. However, some of these food poisoning bacteria can survive the low pH of the stomach (~2.0) long enough to cause illness, so relying on a low pH alone is not adequate. Bryan of Sui Generis Blog recommends a pH of 4.5 or less, the use of well sanitized equipment, and monitoring the starter for the rapid onset of fermentation without putrid smells. Some oxidative yeasts that are the first "barriers" to bacterial growth may be inhibited at 4.0 pH <ref name="BryanMTF"></ref>.
* The risk of botulism toxin is extremely low, but not zero. Generally, ''C. botulism'' is not able to grow and produce toxin in low protein (non-meats) substances at a pH lower than 4.6 <ref>[http://www.ingentaconnect.com/content/iafp/jfp/1982/00000045/00000003/art00005 Toxin Production by Clostridium Botulinum in Media at pH Lower Than 4.6. Nobumasa, Tanaka. Journal of Food Protection®, Number 3, February 1982, pp. 214-284, pp. 234-237(4)]</ref><ref>[http://edis.ifas.ufl.edu/fs104 Preventing Foodborne Illness: Clostridium botulinum. University of Florida IFAS Extension. Retrieved 7/5/2015.]</ref>. However, proteins in the wort may allow growth at a lower pH than 4.6 (studies have not been done on wort, only on meats) <ref name="BryanMTF"></ref>. The presence of more than 5% oxygen in the wort will also reduce the risk <ref>[http://www.ncbi.nlm.nih.gov/pubmed/15895734 Growth and toxin production by Clostridium botulinum in steamed rice aseptically packed under modified atmosphere. Kasai Y, Kimura B, Kawasaki S, Fukaya T, Sakuma K, Fujii T. May 2005.]</ref>.
====Videos====
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==References==