Fermentation Process in Coffee and the Effect on Flavour; A Short Overview.
Fermentation Process in Coffee and the Effect on Flavour; A Short Overview.
Fermentation is a series of chemical reactions involving yeast and bacteria, and in the case of coffee, the mucilage layer of the cherry. Within this layer of the coffee cherry, the mucilage contains sugars, water and starch. When picked, and during processing, this combination starts a natural fermentation process, which produces by-products of acids, alcohols and enzymes, whilst concurrently physically breaking down the mucilage layer (Haile & Kang, 2019).
The natural fermentation process of the coffee cherry produces by-products or metabolites, that increase the amount of free sugars and amino acids surrounding the coffee bean, which are important during a key coffee roasting phase, the Maillard reaction, for flavour and acidity (De Maria et al., 2019).
There are 2 ways fermentation takes place during coffee processing and both allow different microorganisms to interact with the coffee:
Aerobic: Requires oxygen and occurs when the coffee cherries have been picked and left in a tank. With careful monitoring of time and temperature, enhances sweetness and fruitiness (Grind, 2019).
Anaerobic: No oxygen. This occurs when the coffee cherries have been placed in a tank of water and help extend fermentation. The effect on the coffee is a softer body, more complex acidity and refined flavours (Grind, 2019).
Fermentation occurs concurrently during coffee processing. By utilizing either dry (aerobic) or wet (anaerobic) or a combination of both fermentation processes, as such coffee producers can experiment to enhance and drive desired flavour profiles.
Here's our feature S.O that experiments with fermentation from the the land of Colombia:
References:
Mesfin, Kang, & Hee, W. (2019, March 07). The Role of Microbes in Coffee Fermentation and Their Impact on Coffee Quality. Retrieved July 13, 2019, from https://www.hindawi.com/journals/jfq/2019/4836709/
De Maria, C., Trugo, L., Neto, F., Moreira, R. and Alviano, C. (2019). Composition of green coffee water-soluble fractions and identification of volatiles formed during roasting.
Grind, P. (2019). Coffee Fermentation: What Is It & How Can It Improve Coffee Quality?. [online] Perfect Daily Grind. Available at: https://www.perfectdailygrind.com/2018/06/coffee-fermentation-what-is-it-how-can-it-improve-coffee-quality/ [Accessed 13 Jul. 2019].