What Does Thermal Shock Process Mean?
Is this the coolest name for a coffee processing method? Most definitely. Can thermal shock coffees taste delicious? No doubt about it.
Thermal shock processing originated at Finca el Paraiso, an innovative farm in the Cauca Department of Colombia. Diego Bermudez and Wilton Benitez—two names you may recognize from the Black & White menu—partnered at this farm during the creation of this signature process. Diego Bermudez’s Red Plum release rocked the coffee industry, causing many to insist the coffee was infused with additives, while its bouquet of flavor originated only from intentional, intensive processing.
The namesake of thermal shock processing relates to heating and rapid cooling of the coffee during the fermentation process. While it’s tempting to define thermal shock as a monolithic concept, the temperature adjustment is only one stage of the fermentation. A thermal shock may be employed before de-pulping at the beginning of a washed process, as is the case with Paola Trujillo’s SL28 Thermal Shock release. More typically, however, a thermal shock is one part in a multi-step, intensive processing method, as is the case with coffees from Wilton Benitez and Diego Bermudez. Diego and Wilton sterilize their coffee fruit with ozonated water, reducing the native microbial load on the fruit. Wilton takes an extra sterilization step by employing ultraviolet light to eliminate any remaining microorganisms. This decontaminated fruit moves into an anaerobic environment to begin fermentation.
Using signature yeast strains selected from wild samples, the producers pitch yeast culture into the fermentation tanks. Most coffee ferments only with its wild yeast, yet Wilton and Diego manipulate this culture to ensure a controlled process that produces a designated result. The yeast consumes sugars in the fruit, breaking down its mucilage and acidifying the tank’s contents. Once coffee is removed from these initial tanks, the juice is preserved and fed with more yeast to develop a stronger culture. The coffee is fully de-pulped, then left to anaerobically ferment in the juice, before transference to a final aerobic fermentation step, which lasts longer than either of the two previous steps.
At the end of this fermentation journey, the thermal shock takes place. The coffee is heated in its juices, up to a temperature between 104 and 122 degrees Fahrenheit. The theory behind this step is to expand the pores of the coffee, allowing the seeds to absorb more of the juice’s esters, before the seeds are cleaned with cold water. Around 50 degrees Fahrenheit, this shock causes the contraction of pores, locking in the essences of the juice. It’s possible that the rapid heating and cooling of the coffee also halts enzymatic processes in the coffee, as is the case in vegetable blanching. However, as with many elements of coffee processing, scientific research is needed to determine the true root of thermal shock’s flavor impact.
While we describe thermal shock as a distinct processing method, it’s important to remember how much it interplays with other steps of the process. The impacts of depulping, yeast inoculation, and oxygen exposure can all have distinct effects on the final cup profile, yet it’s undeniable that the thermal shock itself can also have an intensive impact on the coffee flavor. For now, we’ll set the science aside and simply enjoy the beautiful flavors that thermal shock coffees have to offer. Complex, fragrant, vibrant coffees will always be at the heart of Black & White, no matter how wild or mild their processing may be.
