It is according to the Water book, who reference from
Briggs, et al., Malting and Brewing Science, Vol. 2, Chapmand and Hall, London, 1981.
I haven't read the source material myself, so it could mean in totality, including mashing, but the quote from the Water book is
"Lactic acid is reported to have a flavor threshold of about 400 ppm in beer (referenced to the above book
). The flavor threshold can vary between tasters. Therefore, the 400 ppm threshold may not hold for all individuals. In addition, many beers typically have a low concentration of lactic acid (typically 50 to 300 ppm) naturally, from fermentation by-products (again referenced to above book
). Therefore, it may not be possible to add less than 400 ppm of lactic acid to water for alkalinity reduction without flavor impact."
It's funny, because when I just looked up Br'un water, as I remembered something similar there, I found the quotes to be very similar and both reference the same source.
From
Br'un water
4.3.4 Liquid Organic Acids such as Lactic and Acetic Acid can be used for alkalinity reduction and acidification.
Lactic Acid is readily available for brewing use, but it can produce a distinctive “tang” in the flavor profile at high concentration. The lactic acid flavor is typically characterized as smooth. It is a weak acid that can be somewhat safer to handle than other stronger acids. Lactic acid is reported to have a flavor threshold of about 400 ppm in beer (Briggs et al., 1981). The flavor threshold can vary between tasters. Therefore, the 400 ppm threshold may not hold for all individuals. In addition, typical beers (especially German beers) naturally have a low concentration of lactic acid (typically 50 to 300 ppm) from malting, fermentation, and production by-products (Briggs et al., 1981). Therefore, it may not be possible to add 400 ppm of lactic acid to water for alkalinity reduction, without flavor impact. Lactic acid is a monoprotic acid and it consumes 1 part bicarbonate per one part lactic acid. For these reasons, it appears that the maximum alkalinity neutralization that lactic acid could provide for brewing is about 100 to 350 ppm reduction in bicarbonate (82 to 287 ppm alkalinity reduction, as CaCO3) in the water. Lactic acid is quite stable and does not degrade appreciably when stored at room temperature. The shelf life of lactic acid stored at 80°C (176°F) is reported at over 80 years. (www.epa.gov/hpv/pubs/summaries/lactacid/c13462rs.pdf)
EDIT - as I guessed, the quote from Br'un includes
malting, fermentation and production by-products, so it is in totality, not just from fermenation, though it does include fermentation, which is interesting. I guess some lactate is produced in fermentation perhaps? Or perhaps the source just included soured beers, which makes sense.
2nd EDIT - Found this exert that leaves me wanting more info, but anyway, it states that yeast do produce some lactic acid.
pg 38
Yeast - the practical guide to fermentation - White, Zainascheff 2010
"Organic Acids
During fermentation, yeast also produce varying levels of organic acids such as acetic, lactic, butyric, and caproic. In most fermenations, the concentrations produced are below the flavor threshold, which is usually a good thing."
3rd EDIT - Is it possible that instead of all the Pyruvate being broken down by the yeast in the two step process using the enzyme pyruvate decarboxylase and alcohol dehydrogenase into ethanol and NAD+, that some of the pyruvate reacts with NADH and H+ which turns them into lactic acid and NAD+?
Pyruvate + NADH + H(+) becomes Lactate + NAD(+).
4th EDIT - However it is done, it appears that yeast do produce lactic acid during fermentation. It makes up some of the 5% of other by-products when CO2 and ethanol are produced from sugars (first paragraph of attachment)
View attachment J. Biol. Chem.-1948-Fales-1-8.pdf