Acid tolerance starter
An acid tolerance starter (also known as an "acid shock starter") is a special kind of starter that allows yeast to acclimate to an acidic medium. This acid-tolerant yeast is added at bottling to increase the speed and consistency of carbonation in bottle-conditioned aged sour beers. This is also as regarded as the most effective technique to reduce or eliminate the formation of the THP off flavor. If yeast added at bottling has NOT developed acid tolerance, it suffers from "acid shock", which results in poor performance.[1][2][3]
Original methods have involved using sour beer in a yeast starter, which has some notable disadvantages. Here we are in the process of developing a modern method of acclimating the yeast to acid, one which does not require the use of sour beer.
Modern protocol
These instructions are for a 5 gallon (20L) batch, with a target pitch rate of approximately 2.5 million cells per mL (assuming 20B cells/g).
Rehydration medium:
- 2g EC-1118 yeast
- 2.5g Go-Ferm
- 50mL filtered water
Acidic medium:
- 10g dextrose
- 2mL 88% lactic acid (yields 1.17% lactic acid in 150mL)
- 1mL 5% acetic acid (yields 0.03% acetic acid in 150mL)
- Top up to 100mL with filtered water (about 91mL is needed)
Process:[4]
- Heat 50mL water in a beaker to dissolve the Go-Ferm and then allow it to cool to 104°F (40°C).
- Heat a larger container of water to 104°F (40°C) to act as a water bath to help hold temperature.
- Sprinkle in the yeast and put the beaker in the bowl (water bath) to help maintain temperature. Do not stir.
- Wait 20 minutes.
- Remove the yeast from the water bath, stir gently, and begin attemperation with the acidic medium:
- Slowly over the course of 5 minutes add 50mL of the growth medium.
- Wait 5 minutes.
- Slowly add the remaining 50mL
- Cover and place on a stir plate for 8-12 hours on low speed.
- Optional: allow the yeast to settle for a few hours so that it can be decanted before pitching.
- Add the yeast to the beer halfway through racking (do not add it directly to priming sugar solution).
Potential sources
- "Effects of acetic acid and lactic acid on the growth of Saccharomyces. cerevisiae in a minimal medium."
- "Influence of medium buffering capacity on inhibition of Saccharomyces cerevisiae growth by acetic and lactic acids."
- "Effect of pitching yeast preparation on the refermentation of beer in bottles"
- "Non-Saccharomyces killer toxins: Possible biocontrol agents against Brettanomyces in wine?"
- "Wine Yeast in Beer"
- https://www.facebook.com/groups/MilkTheFunk/permalink/1363395580355319/?comment_id=1364119323616278&reply_comment_id=1364521000242777&comment_tracking=%7B%22tn%22%3A%22R9%22%7D
- https://beerandbrewing.com/understanding-ph-and-titratable-acidity-in-sour-beer-tools-for-brewers-and/
- https://www.thebeveragepeople.com/how-to/beer/articles/adjusting-sour-beer-acidity.html
- https://www.perkinelmer.com/lab-solutions/resources/docs/APP-analysis-of-lactic-and-acetic-acids-in-sour-beers-by-HPLC.pdf
References
- ↑ Blair, J. "Terminal Acidic Shock and Sour Ale Bottle Conditioning." The Rare Barrel. December 2017.
- ↑ Rogers, CM., et al. "Terminal acidic shock inhibits sour beer bottle conditioning by Saccharomyces cerevisiae." Food Microbiology, vol. 57, 2016, pp. 151-158.
- ↑ "Packaging - Acid Shock Starter." Milk the Funk wiki. Accessed May 2020.
- ↑ "Easy Steps for Optimal Yeast Rehydration." Scott Labs. Accessed online May 2020.