Briefly heats cherry or parchment (about 85 C) and then chills it in cold water to cut unwanted microbes before controlled fermentation.
Thermal shock is an additional step, not a fermentation itself: coffee is briefly heated (about 85 C for roughly 30 seconds, or steamed) and then cooled fast in water at about 5-15 C. It is meant to cut unwanted microbes and enzymes while preserving the embryo, which can let producers control the fermentation that follows. Done badly it can kill the embryo or invite acetic fermentation. Paired with anaerobic fermentation it is reported to give sweeter, fruitier cups.
How it worksThe coffee is immersed in hot water (about 85 C for roughly 30 seconds) or steamed, then quickly cooled in clean water at about 5-15 C. The aim is to reduce populations of undesirable microorganisms and unwanted enzymes while sparing the seed embryo, so selected microbes can then drive fermentation.
Step by step
- 01
Heat the coffee briefly with hot water or steam.
- 02
Cool it immediately in clean water at about 5-15 C.
- 03
Proceed to fermentation, often anaerobic, sometimes with selected microbial strains.
Timing · Heat treatment of roughly 30 seconds in one described protocol, followed by a longer fermentation.
History
Described as a recent technique inspired by pasteurization and blanching in other industries, with applications still being explored.
Our notes on Thermal Shock are still being checked against their sources, so for now this page shows only the facts we can stand behind.
What can go wrong
- Excess heat can kill the seed embryo. Poor temperature control also risks acetic fermentation and unpleasant flavors.
In the cup, according to guides
- SweetnessMoreCombined with anaerobic fermentation, reported to give sweeter, fruitier and less astringent cups.
A variant of
At the same stage