Fermentation and special processes — seven techniques behind the names

On top of base processes such as Washed, Natural and Honey, techniques that design the course of fermentation itself in detail have been increasing in recent years. The seven covered here are all less independent processes than "additional designs" layered onto a base process. Even when the name is written on the label, it does not tell you the whole process.

To check where each one sits in a diagram, see Comparing processes as well.

Lactic Fermentation

Fermentation designed to use or encourage the activity of lactic acid bacteria and the production of lactic acid. Lactic acid bacteria tend to dominate in low-oxygen conditions, so it is often done in combination with Anaerobic in sealed tanks.

Lactic acid is gentler than the citric acid common in citrus or the malic acid common in apples. It is sometimes chosen to aim for a mellow, yogurt-like acidity and a rounded texture. On the other hand, if fermentation goes too far, the acidity can turn muddy or dairy-like aromas can become too strong.

Inoculated Fermentation

A technique that controls fermentation by adding selected yeasts or microorganisms. With spontaneous fermentation, results swing with the day's temperature and the microorganisms on the fruit. Adding yeasts such as those used in wine or beer brewing aims to even out the course of fermentation for better reproducibility, or to draw out particular aromas.

But adding yeast does not guarantee higher quality. Which strain, at what stage, in what amount? Research is still ongoing, and producers are still at the stage of trial and error.

Thermal Shock

A technique that includes washing fermented beans in succession with water at different temperatures. It is generally described as using warm water and then cold water. Its stated aims are to fix the aromas created in fermentation into the beans and to stop fermentation at that point, but the mechanism of its effect has not yet been sufficiently verified.

The technique spread mainly among some producers in Colombia, and it is almost always used in combination with other fermentation designs such as Anaerobic. For now it is reasonable to understand it as a step for adjusting the outline of the flavor and the impression in the cup.

Koji Fermentation

An attempt to apply koji mold (Aspergillus oryzae), familiar from making sake, miso and soy sauce, to coffee processing. It aims to design flavor by using the enzymes the mold produces to break down and transform components of the beans.

It is familiar in Japanese brewing, but in coffee it is still experimental and cannot be called a standard process. As one of the special steps, it needs to be watched as further verification comes in.

Submerged Fermentation

A method of fermenting cherries, or pulped beans, submerged in water. The fermentation tanks of traditional Washed processing can also be called a kind of submerged fermentation.

Because submerging limits contact with air, it is sometimes treated as the same thing as Anaerobic, but the two are not necessarily the same. Some oxygen is dissolved in water, and how anaerobic conditions become depends on the tank design, water changes and how it is managed.

Extended Fermentation

A design that ferments for longer than usual: several dozen hours, sometimes several days or more. It aims to strengthen fermentation aromas and fruit, but taken too far it leads to sharp, vinegar-like smells and unpleasant fermentation off-notes.

Time alone does not decide flavor or quality. Even at the same length of time, fermentation proceeds completely differently at different temperatures. You need to check "at what temperature" as well as "how many hours".

Co-fermented and Infused

Techniques that add fruit, spices, yeast and so on, or ferment the coffee together with other ingredients. Some lots with striking aromas reminiscent of fruit or cinnamon have been through steps like these.

What is worth distinguishing here is whether the aroma of the added ingredient itself has transferred to the beans (Infused) or microorganisms have fermented using the added ingredient as food and their products have become the aroma (Co-fermented). The steps differ by producer, and the line between the two is not always clear.

How coffee with added flavorings or fruit should be labeled is still being debated in the industry. What matters as a buyer is whether the seller can explain what was added, and when and how.

Reading past the name

What the seven techniques have in common is that the name alone does not tell you the steps. Even if a label says lactic fermentation, you cannot tell whether lactic acid bacteria were added or conditions were set so that they multiplied naturally. Fermentation conditions, time, temperature, what was added. Only when you have checked that far can you see what a lot was made to achieve.