Experimental processing guide - lactic fermentation

In our ongoing guide to the kind of experimental coffees you will find at Sticky Toffee Coffee, we take a look at lactic fermentation

For us at Sticky Toffee Coffee, lactic fermentation means almost a guarantee of one thing: a creamy, almost milkshake like quality to the coffee we roast. Think mango lassi or strawberry shake. These coffees are still quite rare but what is the process behind them?

Coffee production involves a range of yeast and cultures, with the dominant one being determined by the environment during fermentation. To foster a lactic fermentation, coffee producers aim to create ideal conditions for lactobacillus cultures, which are the same type used in dairy production and generate lactic acid.

To achieve a lactic fermentation, coffee producers carefully choose perfectly ripe cherries with a high sugar content and place them in a tank or sealed barrel, creating anaerobic conditions. Throughout the fermentation process, the producer closely monitors and adjusts temperature, pH levels, and oxygen to encourage the growth of lactobacillus.

Lactic fermentation can be applied to both whole cherries and pulped beans. Therefore, you may encounter terms such as "Lactic Washed," which means the coffee was pulped, lactic fermented, and dried, or "Lactic Natural," which indicates that the coffee was lactic fermented and dried with the cherry skin and fruit still intact.