Description
Traditional method of carbonating lagers by introducing actively fermenting wort to trigger secondary fermentation.
Technical
Utilizes Saccharomyces pastorianus yeast consuming fermentable sugars to produce CO2 (carbonation) and ethanol while metabolizing off-flavor compounds like diacetyl. The process involves adding 10-20% krausen (young beer at peak fermentation) to fully fermented lager.
Culinary Significance
Produces finer, more persistent carbonation than forced carbonation while improving flavor maturation through yeast activity.
Science
Primary Reaction
C6H12O6 → 2C2H5OH + 2CO2 (alcoholic fermentation)
Parameters
Temperature
12°C optimal
10°C to 13°C range
Time
2 weeks
7 days – 4 weeks
Equipment
Pressure-rated fermentation vesselHydrometerYeast propagation system