Anaerobic and Experimental Processing in India

"Anaerobic" means fermentation in the absence of oxygen. That is all it means.

It does not specify how long, at what temperature, with what starting material, in what vessel, or whether anything was added. Two coffees both truthfully labelled anaerobic can have been made by entirely different processes and taste nothing alike.

What actually happens

In conventional washed processing, mucilage breaks down in tanks open to the air. Yeasts and bacteria work, oxygen is present, and the microbial population that develops is the one that does well in those conditions.

Seal the vessel — typically a tank with a one-way valve that lets CO₂ escape without letting air in — and the population shifts. Lactic acid bacteria do comparatively better; the acids produced differ; and the compounds that end up in the seed differ with them.

Variants you will meet:

• Anaerobic washed — sealed fermentation, then washed and dried.
• Anaerobic natural — whole cherry sealed, then dried in fruit.
• Carbonic maceration — whole cherry in a sealed vessel flushed with CO₂, borrowed from winemaking.
• Yeast-inoculated — a selected culture added rather than relying on ambient flora.
• Extended fermentation — long, sometimes cooled, sometimes anaerobic.

What it reliably does

Increases intensity. Anaerobic lots are typically more aromatic and more assertive than the same coffee processed conventionally.

Shifts the flavour towards fermented and boozy notes — tropical fruit, wine, sometimes cinnamon or clove — depending on the variables.

Increases variability between lots, because the process is more sensitive to conditions than conventional washing.

What it does not do

It does not improve a poor coffee. It changes it. An under-ripe, poorly picked lot fermented anaerobically produces an intense, distinctive, poor coffee.

It does not guarantee anything about quality. The word on a bag carries no specification, unlike a screen size or a moisture figure.

It does not make origin character clearer. Usually the opposite: process character increasingly dominates, and at the far end you can no longer taste where the coffee is from. Whether that is a cost depends on why you bought it.

The honest reservation

There is a real argument in the trade that heavily processed coffees are competing on novelty rather than agriculture, and that a lot of what buyers pay a premium for is fermentation flavour that could have been produced on almost any base coffee.

That argument has force. It is also not a reason to dismiss the category — controlled fermentation is a legitimate tool, and some producers use it with real precision. The distinction is between processing as a technique and processing as a disguise, and the questions below are how you tell.

The questions that separate the two

• What was the base coffee? Variety, altitude, picking selection. A producer who cannot describe it was not thinking about it.
• How long, and at what temperature? Sealed fermentation generates heat. Uncontrolled temperature is the main cause of the lot going from distinctive to defective.
• Was pH monitored? Fermentation is tracked by pH more usefully than by clock. A producer measuring it is controlling the process.
• What vessel, and how was CO₂ managed?
• Was anything inoculated or added? This should be disclosed and often is not.
• How consistent is it lot to lot?

A producer with answers is running a process. One who has only the word is running a fashion.

In India

Experimental processing is growing on Indian estates, and the country's conditions make it interesting: high ambient temperatures make temperature control the binding constraint, and the shade canopy moderates that at origin more than in a sun-grown system.

Indian terminology in this space is as loose as everyone else's, so the same rule applies as for honey and pulped natural — get the process described, not labelled.

Buying it

Anaerobic lots are small, expensive and variable. They work as a rotating single origin with a story, and poorly as a permanent line item.

Sample every lot. Do not contract forward on the strength of last season's version, because with this process last season's version is a weaker guide than usual.

Hoysala ferments anaerobically, for 72 hours.

For the fundamentals underneath all of this, see fermentation control.