LAB Fermentation - more complete understanding
In another post, we drifted off to a discussion of Lactic Acid Bacteria (LAB). This subject needs a post of it’s own.
The question was posed, “why is it that Yeast Water (YW) doesn’t contain high amount of LAB”? YW are known to produced non-sour tasting products.
Michael, aka “mwilson” replied with an extremely informative and scientifically based answer. Here is a copy from that post.
”LAB fermentation has been utilised for centuries as a way to make foods stable, less susceptible to spoilage and suitable for long term storage.
Many mistakenly think that LAB favour an acidic environment. In actual case LAB are responsible for making the environment acidic. Unlike yeasts their growth is very pH dependent.
SD starters often range between pH 3.7-6 and many SD specific LAB stop growing below pH 4. LAB prefer only mildly acidic environments. E.g. vegetables, grains, meats which are around pH 5-7.5.
Yeast waters will often stabilise at around pH 3.5 since many fruits are somewhere close to this pH. At this low pH, growth of LAB is not favourable.
Other factors relate to nutrition including, available protein sources of which LAB and yeasts generally have a different preference of type.
LAB thrive in SD starters because we bakers refresh them, which brings the pH back up to around pH 6 (the pH of flour). As the dough or batter ferments and become more acidic their growth continues to slow and eventually stops.”