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Cocoa, coffee and spice from Brazil

Self-induced anaerobic fermentation (SIAF) of coffee

SIAF is a wet-process coffee fermentation done in a closed tank with an airlock, so the CO₂ made by the beans' own microbes pushes out the air. In a Brazilian study, 175 kg of pulped arabica beans in 30 L of water were fermented for 24, 48 or 72 hours while the pH fell from 5.8 to 4.4, then washed and dried to about 12 % moisture. All lots scored 84 or more as specialty coffee.

Fully documentedCocoa, coffee and spice24 h – 3 days

Recipe

Amounts from a sourceOne study tank of 175 kg beans in 30 L water (Vale et al. 2022). The full-washed process uses 2 to 10 L water per kg of fresh cherry (FAO Lao manual).
Pulped arabica coffee beans, with mucilageabout 175 kg[vale2022]
Water, decontaminated with ozone30 L[vale2022]
Starterspontaneous

Total time across the recorded steps: 24 h – 3 days

Start
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What changes: Starting material: freshly pulped arabica beans still coated in sweet mucilage

Step 1 of 4
Pick and pulp ripe cherries
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactobacillus

The study cherries were picked in July 2021 and pulped by machine. FAO advises processing only ripe red cherries, on the day they are picked.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

SIAF is a wet-process coffee fermentation done in a closed tank with an airlock, so the CO₂ made by the beans' own microbes pushes out the air. In a Brazilian study, 175 kg of pulped arabica beans in 30 L of water were fermented for 24, 48 or 72 hours while the pH fell from 5.8 to 4.4, then washed and dried to about 12 % moisture. All lots scored 84 or more as specialty coffee. Made in 4 steps over 24 h – 3 days. The longest step, seal in a tank with an airlock, takes 24 h – 3 days (da Silva Vale A 2022). Lactobacillaceae (mainly Lactobacillus), about 20 % of bacterial reads in all layers by 72 h and Leuconostoc do most of the fermenting.

Key numbers
Main step24 h – 3 daysReported[vale2022]Seal in a tank with an airlock
AciditypH 5.8 → 4.4Measured[vale2022]Seal in a tank with an airlock

What makes this one different

The standard wet-process ferment in a closed tank with an airlock instead of an open tank, so the ferment runs without air. The microbes differ from open-tank ferments, with many enterobacteria and moulds and few lactic bacteria and yeasts.

Cup score
All beverages from 24, 48 and 72 h fermentations scored 84 or more and were classed as specialty coffee
Full-washed process
FAO's Lao manual lets the mucilage ferment over one to two days before washing; FAO's Kenya notes give 1 to 4 days depending on conditions

Related ferments

Variants

  • Carbonic macerationCO₂ is added from outside rather than made by the beans' own microbes; Vale et al. cite a 2022 study of carbonic maceration of Coffea canephora var. Conilon.

Safety

Over-fermentation, mould, taints and odours spoil coffee quality, and the loss cannot be undone (FAO Lao manual). Mould risk during drying is covered in the coffee wet process entry.

History and sources

Every number is labelled with how it is known. How this atlas is made

Vale et al. (2022) describe SIAF as a recently proposed low-cost method for coffee growers. They note that stirred-tank reactors with starter cultures raised cup scores by about 8 points but need an investment of about USD 1.4 million, which limits their use by small producers.

  1. [vale2022] da Silva Vale A., Balla G., Rodrigues L.R.S., de Carvalho Neto D.P., Soccol C.R., de Melo Pereira G.V. 2022, Understanding the Effects of Self-Induced Anaerobic Fermentation on Coffee Beans Quality - Microbiological, Metabolic, and Sensory Studies, Foods 12(1):37, doi:10.3390/foods12010037paper
  2. [fao-lao2005] Winston E., Op de Laak J., Marsh T., Lempke H., Chapman K. 2005, Arabica coffee manual for Lao PDR, chapter 6 Harvesting and processing, FAO Regional Office for Asia and the Pacific, Bangkokgov
  3. [fao-kenya2000] Mutua J. 2000, Post harvest handling and processing of coffee in African countries, Annex 5 Coffee post harvest handling and processing in Kenya, FAO AGSIgov