SilentAutumn
Well-Known Member
http://phys.org/news/2016-03-biochemist-solution-acid-craft-brewers.html
Came across this today. Since a lot of people are attempting sours, though they might find it interesting.
Terminal acid shock occurs when craft brewers add extra yeast to beers after fermentation to create carbonation prior to bottling, the final step in the traditional brewing process. The issue typically doesn't affect larger commercial breweries that employ forced carbonation.
The beer used in the experiment was developed by Upland Brewing, whose previous attempts to brew a variety of sour beer, called "Cauldron," failed two years in a row due to complications during the bottling phase, resulting in the loss of 1,600 gallons of beer. The variety, aged in charred oak barrels filled with Michigan cherries, has a pH level of 3, a typical acidity for many sour beers.
....
This slowed metabolism is responsible for the microbes' failure to "exhale" the carbon dioxide that creates carbonation during bottling. But the fact the majority of the yeast survived meant the researchers found they could revive the microorganism through incubation in a nutritionally dense substance typically used in labs called YPD, which contains yeast extract, peptides and sugar.
"Normally breweries simply re-hydrate dry yeast with water and sugar prior to bottling, but sours are too harsh," Bochman said. "Exposing the yeast to a mixture of YPD and the uncarbonated beer a day prior to bottling strengthens the microbes enough to survive a highly acidic environment."
Came across this today. Since a lot of people are attempting sours, though they might find it interesting.
Terminal acid shock occurs when craft brewers add extra yeast to beers after fermentation to create carbonation prior to bottling, the final step in the traditional brewing process. The issue typically doesn't affect larger commercial breweries that employ forced carbonation.
The beer used in the experiment was developed by Upland Brewing, whose previous attempts to brew a variety of sour beer, called "Cauldron," failed two years in a row due to complications during the bottling phase, resulting in the loss of 1,600 gallons of beer. The variety, aged in charred oak barrels filled with Michigan cherries, has a pH level of 3, a typical acidity for many sour beers.
....
This slowed metabolism is responsible for the microbes' failure to "exhale" the carbon dioxide that creates carbonation during bottling. But the fact the majority of the yeast survived meant the researchers found they could revive the microorganism through incubation in a nutritionally dense substance typically used in labs called YPD, which contains yeast extract, peptides and sugar.
"Normally breweries simply re-hydrate dry yeast with water and sugar prior to bottling, but sours are too harsh," Bochman said. "Exposing the yeast to a mixture of YPD and the uncarbonated beer a day prior to bottling strengthens the microbes enough to survive a highly acidic environment."
