Thermal shock processing is a technique to improve the taste and quality of coffee beans. The beans are exposed to rapid temperature fluctuations in order to change their internal structure and chemical composition. This can be done in a number of ways, but the most common method is using dry ice or liquid nitrogen.
The coffee thermal shock process
Heat shock treatment starts with choosing the right beans. Different types of beans can respond differently to processing, so it’s important to choose beans that are known for their flavor and quality. Once selected, they are prepared for shock by removing excess moisture or contaminants.
They are then subjected to rapid temperature changes. This can be done with dry ice, liquid nitrogen, or other methods depending on the desired temperature and duration of the shock. As a rule, the grains are cooled to a temperature of -50°C to -80°C and then rapidly heated to a temperature of 30°C to 60°C.
After the shock, the beans are cooled and left to rest for a period of time. This allows the oils and flavors to redistribute and stabilize in the beans. Once the beans have rested, they can be roasted and ground.
Why is coffee thermal shock treated?
The purpose of the thermal shock treatment is to alter the beans to enhance their flavor and aroma. It is believed that the rapid temperature changes cause cracks in the beans, allowing the coffee’s oils and aromas to be released more easily. This can result in a more complex and nuanced flavor profile, as well as a smoother and more balanced cup of coffee.
Factors affecting heat shock treatment of coffee
There are several factors that can affect the effectiveness of heat shock treatment, such as: e.g.:
- The type of beans used
- The temperature
- The duration of the shock
- The method of application
Different techniques can produce different results, so it’s important for roasters to experiment and find the method that best suits their beans and desired flavor profile.
Benefits of thermal shock treatment of coffee
One of the main advantages of heat shock treatment is that it can be performed quickly and efficiently.
It is a relatively simple procedure that requires no special equipment or training. This makes it an attractive option for small roasters that don’t have the resources or expertise to invest in more complex processing methods.
Disadvantages of thermal shock treatment of coffee
Thermal shock treatment is not without disadvantages. One of the main problems is that the beans can be modified to reduce their shelf life.
Rapid temperature changes can make the beans brittle and prone to breakage, making them more susceptible to spoilage over time. This can be particularly problematic for specialty roasters who rely on high-quality beans with a longer shelf life.
Another potential problem with thermal shock treatment is that it may not produce consistent results. Because the technique relies on rapid changes in temperature, it can be difficult to control the exact effects on the beans. This can make it difficult for roasters to reproduce the desired flavor profile from batch to batch.
Despite these concerns, thermal shock treatment has earned a reputation as a reliable and effective method of improving the flavor and quality of coffee beans. Many roasters have found this method to add depth and complexity to their coffees, and it’s becoming a popular way to experiment with new and innovative flavors.
Parts of the coffee bean and heat shock treatment
To understand the science behind heat shock processing, it makes sense to look at the basic anatomy of the coffee bean. Coffee beans are made up of several different layers, such as the outer skin, the parchment, and the inner seed. Each of these layers plays a unique role in the flavor and overall quality of the coffee.
The outer skin of the coffee
Also called exocarp, it is a thin layer that envelops the bean. It consists mainly of cellulose and pectin and serves as a protective layer for the rest of the bean. The shell is relatively tasteless and does not contribute significantly to the taste of the coffee.
The parchment or mesocarp of the coffee bean
This is the next layer of the bean. It is a thin layer of paper that surrounds the bean and provides support and protection. The parchment contains a number of oils and aromas that can contribute to the overall flavor and aroma of the coffee.
The inner seed or endocarp of the coffee bean
This is the central part of the bean. It stores coffee’s oils and flavors and is the part of the bean that is roasted and ground to make coffee. The bean consists of several layers:
- The Husk: This is the outermost layer of the seed and serves to protect the cotyledon and endosperm.
- The cotyledon: The cotyledon is the main source of nutrients for the developing plant and also stores the coffee’s oils and aromas.
- The endosperm: It is the innermost layer of the seed and provides energy and nutrients to the developing plant.
Heat shock treatment is an effective way to improve the taste and quality of coffee beans. While not without difficulties and limitations, it is a simple and effective technique that can be used by roasters of all sizes to create truly exceptional coffees. It is a good choice for coffee roasters who want to produce quality coffee that stands out.