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Contamination issues seem to be the biggest challenge When working with prelactic acid-souring wort with ''Lactobacillus''. This producing bacteria, the brewer’s goal is because ''Lactobacillus'' does not fully ferment wort by itself (see [[100%25_Lactobacillus_Fermentation|100% ''Lactobacillus'' fermentation]]). When yeast fully ferments wort into beerusually to attain clean-tasting sourness, alcohol, hopswhile obtaining desirable flavor contributions from these bacteria, and a low pH all work together to help prevent other microorganisms from contaminating the beer (although contamination can certainly happen with beer spoilage microbes such as ''Brettanomyces'', ''Pediococcus'', etc.) <ref>[http://suigenerisbrewing.blogspot.com/2014/02/fact-or-fiction-can-pathogenssimultaneously minimizing off-surviveflavors.html "Fact or Fiction? Can Pathogens Survive in Beer?" Sui Generis Blog. 02/18/2014. Retrieved 11/10/2016.]</ref>. When fermenting with ''Lactobacillus'' It should be noted that off flavors span the range from undesired by itselfmost, either no alcohol is produced or not enough alcohol is produced to have an antimicrobial effectdesirable to some. Usually hops are not used when souring wort with ''Lactobacillus'' because even small amounts of hops completely inhibit most commercial strainsFor example, so other microbes isovaleric acid is a compound known for its footy aroma that are sensitive to hops are also not inhibited. The high available sugars, warm temperatures typically used would be considered an off flavor in souring wortmany beers, and yet it gives a lack of alcohol/hops therefore increase the chances for contamination during souring wort with ''Lactobacillus''highly desired flavor to certain French cheeses.

Contaminations can have a variety of effects on soured wort depending on the type of microbe(s) With that caused said, contamination issues are among the contaminationbiggest challenges when pre-souring wort with ''Lactobacillus''. One typical off-flavor in kettle sour beers This is because ''Lactobacillus'' does not fully ferment wort by itself (see [[Butyric_Acid100%25_Lactobacillus_Fermentation|butyric acid100% ''Lactobacillus'' fermentation]], which is in and smells like human vomit). Although the exact source of butyric acid in kettle soured beers has not been identified scientifically that we know ofWhen yeast fully ferments wort into beer, alcohol, hops, butyric acid is produced by anaerobic contaminates and a low pH all work together to prevent most spoilage microorganisms from contaminating the beer (although contamination can certainly happen with beer spoilage microbes such as ''Brettanomyces'', 'not'Pediococcus'' when , etc.) <ref>[http://suigenerisbrewing.blogspot.com/2014/02/fact-or-fiction-can-pathogens-survive.html "Fact or Fiction? Can Pathogens Survive in Beer?" Sui Generis Blog. 02/18/2014. Retrieved 11/10/2016.]</ref>. When fermenting with ''Lactobacillus'' by itself, either no alcohol is produced or not enough alcohol is exposed produced to oxygen (see [[have an antimicrobial effect. Usually hops are not used when souring wort with ''Lactobacillus#Effects_of_Oxygen|Effects '' because even small amounts of hops completely inhibit most commercial strains, but they also inhibit some spoilage microorganisms. The high available sugars, warm temperatures typically used in souring wort, and a lack of Oxygen on alcohol and hops therefore increases the chances for contamination during souring wort with ''Lactobacillus'']] and [[Butyric_Acid|butyric acid]]). [[Isovaleric_Acid|Isovaleric acid]] is another off-flavor that can be produced by both anaerobic and aerobic contaminates.

Another very typical contaminate during souring Contaminates can include a variety of molds, yeasts, and bacteria. Contaminations can have a variety of potentially unfavorable flavor effects on soured wort with ''Lactobacillus'' is actually brewer'depending on the type of microbe(s yeast (''S. cerevisiae'')that caused the contamination. Brewer's yeast One common off-flavor in kettle soured beers has been associated with [[Butyric_Acid|butyric acid]], which is not greatly inhibited by ''Lactobacillus''in and smells like human vomit. Conversely,''Lactobacillus'' is greatly inhibited by Although the presence exact source of active ''S. cerevisiae'' <ref name="Hubbe">[https://www.facebook.com/groups/MilkTheFunk/1407620505932826/ Effect butyric acid in kettle soured beers has not been identified that we know of mixed cultures on microbiological development in Berliner Weisse (master thesis). Thomas Hübbe. 2016.]</ref>, butyric acid is produced by anaerobic contaminates and the warmer temperatures encourage ''S. cerevisiae'not'' to ferment the wort quickly. This often results in a beer that isn't sour because the when ''Lactobacillus'' are out-competed by the yeast. Signs that yeast has contaminated the wort include the typical signs of yeast fermentation: the presence of a krausen, a gravity shift of more than 1.005 gravity points is exposed to oxygen (or 0.5-1.0° Plato), and looking at a sample of the wort under a microscope. Sources of yeast contamination can come from poor sanitation, but they can also come from the yeast manufacturer themselves. See see [[100%25_Lactobacillus_FermentationLactobacillus#Effects_of_Oxygen|100% Effects of Oxygen on ''Lactobacillus'' fermentation]] for more informationand [[Butyric_Acid|butyric acid]]). [[Isovaleric_Acid|Isovaleric acid]] is another off-flavor that can be produced by both anaerobic and aerobic contaminates.

Another common contaminate from improper wort souring is brewer's yeast (''S. cerevisiae''). Brewer's yeast is not greatly inhibited by ''Lactobacillus''. Conversely, ''Lactobacillus'' is greatly inhibited by the presence of active ''S. cerevisiae'' <ref name="Hubbe">[https://www.facebook.com/groups/MilkTheFunk/1407620505932826/ Effect of mixed cultures on microbiological development in Berliner Weisse (master thesis). Thomas Hübbe. 2016.]</ref>. The warmer temperatures encourage ''S. cerevisiae'' to ferment the wort quickly. This often results in a beer that isn't sour because the ''Lactobacillus'' are out-competed by the yeast. Signs that yeast has contaminated the wort include the typical signs of yeast fermentation: the presence of a krausen, a gravity shift of more than 1.005 gravity points (or 0.5-1.0° Plato), and looking at a sample of the wort under a microscope. Sources of yeast contamination can come from poor sanitation, but they can also come from the yeast manufacturer themselves. See see [[100%25_Lactobacillus_Fermentation|100% ''Lactobacillus'' fermentation]] for more information.  Another source of contamination, which can is arguably be considered not actually a contaminationdesired, is happens when using some sort of a "wild" source for the of ''Lactobacillus''. For example, when culturing ''Lactobacillus'' using non-plating techniques from grains, fruit, or from some other fermented food such as kefir, sauerkraut, etc., yeast and other microbes can carry over from the culturing process (see [[Alternative Bacteria Sources]]). The only way to guarantee that only ''Lactobacillus'' from a "wild" source such as these will be fermenting ferment the wort, it must be isolated first is to isolate the microbe using plating techniques (see [[Wild Yeast Isolation]]). Otherwise there is a chance that wild yeast will also survive the culturing process.