Mexico Innovation Extended Fermentation (2021)

The Process

The transformation of coffee cherry to a green coffee bean is a complex biotechnological process. The process involves fermentation where microorganisms (yeast, bacteria and fungi) use the mucilage in the coffee cherry digest the carbohydrates and produce complex metabolites. These metabolites when roasted provide the wonderful coffee aroma and the taste to the cup of coffee.

In this very special lot we took fresh coffee cherry from the Zili and Sampeire families, pulped them carefully, and added a starter culture to the fermentation tank. We allowed the fermentation to extend about two to three times the normal fermentation while monitoring the pH and other indicators. Finally we washed the coffee and dried it.

The secret behind our starter culture is that it changes the microbiological makeup of the fermentation to both encourage good flavor and discourage the negative flavor elements. Hence when evaluating our coffee we found that the extended submerged fermentation using a starter culture generated favorable volatiles such as alcohols, esters which enhanced the fruity and sweetness attributes and reduced unfavorable volatiles such as pyridine, pyrazines and guaiacol resulting in significant improvements to aroma.

A few of the exciting takeaways from this experience. The coffee through this extended fermentation process increased the cup score almost 3 points on the SCA scale. We also measured the aroma fingerprint of theses coffees and they were significantly different from the normal coffee processed in the cherry mill. For this lot the cup profile can sometimes taste like a coffee from East Africa.