We asked Wilton to explain us his acclaimed thermal shock method, and in the following we summarize some of the key points that emerged from our conversation with him.
First of all, Wilton tells us that thermal shock is not a processing method in itself, as can be for instance the usual triad of Natural, Washed and Honey coffees, whose differences we have already explained in our blog post here.
Rather, thermal shock is one more step in the processing of coffee. Thermal shock, as the name suggests, consists of exposing the coffee mass to a succession of high and low temperatures.
Wilton explains that this can be considered similar to the blanching process used in the seafood and vegetable industries, or even in the fermentation process of vanilla.
The process has two phases. The first can be carried out in two ways that both require hot water. One option is using steam to expose the beans at higher temperature; the other one consists of immersing the grains in boiling water. The former has the drawback that it requires the use of specialized machinery with the related increasing costs and investment; the latter must be carried out in controlled conditions (temperature and duration of the process) to avoid burning the beans.
Subsequently, the second phase consists of lowering the temperature of the coffee mass, which is achieved by immersing the coffee in cold water, which can be achieved either with ice or with water at room temperature.
The resulting effect of this process is that the coffee mass is sterilized and homogenized, which prepares it for the subsequent inoculation of specific microorganisms in the fermentation phase. In this way, fermentation and the propagation of desirable microorganisms are encouraged.