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===Dealing With Yeast Contamination===
In the case of accidental yeast contamination, the easiest option is to simply allow the beer to ferment out without doing a second boil to kill the yeast. This decision depends on whether or not the brewer is prepared to deal with having living ''Lactobacillus'' exposed to their cold side equipment (racking equipment, fermenters, etc.; see [[FAQ#Do_I_need_separate_equipment|Do I Need Separate Equipment FAQ]]). The brewer could then maybe decide to make this a [[Mixed Fermentation]] sour beer if they have the fermentation space for it. If the brewer is not willing to expose their cold side equipment to the living ''Lactobacillus'', boiling the fermented/partially fermented beer is another option.
If a yeast contamination produces a significant amount of alcohol during the souring process, then this presents a problem when it comes to boiling. Although 100% pure ethanol boils at 173.1°F/78.4°C <ref name="boiling_of_alcohol">[http://chemistry.about.com/od/moleculecompoundfacts/f/What-Is-The-Boiling-Point-Of-Alcohol.htm Boiling temperature of ethanol]</ref>, the lower the concentration of ethanol in the wort (technically beer at this point if it has been fully attenuated by yeast), the higher the temperature required for boiling off the ethanol. For example, at 5% ABV it takes approximately 197°F/92°C for the ethanol to boil <ref>[http://www.clawhammersupply.com/blogs/moonshine-still-blog/12243869-making-moonshine-still-temperature Making Moonshine: Still Temperature. Retrieved 01/11/2016.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1212116758816536/?comment_id=1212140998814112&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Russell Carpenter on MTF. 01/11/2016.]</ref>. Time is also required to boil off the ethanol, so this may not be as big of a concern as it first appears (''warning: vaporized ethanol is highly flammable)''. Another and perhaps more important consideration is that boiling and high heat pasteurization temperatures can have a negative effect on the flavor of fermented beer. Beer already has anti-bacterial properties, such as low pH, presence of alcohol, and hops (although hops may not be present in wort being soured), so higher pasteurization temperatures aren't necessarily required for beer. For these reasons, the beer industry commonly heat pasteurizes beer at '''140°F/60°C for 15 minutes''', and this is also adequate for pasteurizing soured wort that accidentally fermented do to yeast contamination <ref>[http://www.sciencedirect.com/science/article/pii/S0023643806002854#bib16 A suitable model of microbial survival curves for beer pasteurization. Sencer Buzrul. 2006.]</ref>. Although the yeast will be killed during the pasteurization, so will the ''Lactobacillus'', and the brewer can trust that equipment downstream shouldn't get contaminated. Other options are to simply dump the batch and start again with a pure culture of ''Lactobacillus'', or do not pasteurize and let the ''Lactobacillus'' live. If the ''Lactobacillus'' is not pasteurized and allowed to live, the soured wort/beer should be treated with care so that it does not contaminate the rest of the brewery (see [[FAQ#Do_I_need_separate_equipment|'Do I need Separate Equipment?' FAQ]]). It is possible that the contaminating yeast out-competed the ''Lactobacillus'', which results in not much acid production. If the beer doesn't taste sour, then it is likely to not sour much during aging unless the ''Lactobacillus'' strain is very hardy (alternatively, pitch ''Pediococcus'' or a hardier strain of ''Lactobacillus'' like ''delbruekii'' or ''brevis'' to try and achieve acidity over time). If the contaminating yeast doesn't fully attenuate the wort, pitch a fresh slurry of yeast to finish the fermentation.