Yeast inoculation

Yeast inoculation adds a selected strain of yeast to the fermentation tank rather than relying on whatever microbes are present on the fruit.

The technique comes straight from winemaking, where inoculated fermentation has been standard for decades.

Why producers do it

Control. Wild fermentation depends on ambient microbes, temperature and luck. A known strain in a known quantity produces a repeatable result — which for a producer selling on quality is worth a great deal.

Direction. Different strains produce different compounds. Some push towards tropical fruit, others towards floral or savoury notes. The producer can aim at a profile rather than discover one.

Defect reduction. A strong inoculated culture outcompetes the organisms that cause off-flavours.

The cup

Clean and often intensely flavoured, in a direction chosen by the producer. Less unpredictable than wild anaerobic fermentation and often less funky.

The debate

The same question as all processing innovation: at what point does the process stop revealing the coffee and start replacing it?

Inoculation sits on the acceptable side for most people — it directs a natural fermentation rather than adding flavour. Co-fermentation with added fruit or spices is where most of the industry draws the line, and even that is contested.

Brewing it

Filter, light roast, clean brewer. These lots are usually roasted very light.