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Coffee Fermentation: Reasons To Add Microorganisms
Learn how spontaneous fermentation and selected starter cultures affect coffee processing, and what to ask when comparing a fermented coffee lot.
What microorganisms are present during fermentation?
Fermentation is part of post-harvest coffee processing. Microorganisms associated with the fruit and processing environment use available nutrients and produce metabolites as the coffee is processed.
Spontaneous fermentation
When a producer relies on the existing microbial community rather than adding a selected starter, the process is described as spontaneous fermentation. The community and its activity depend on the coffee and processing conditions.
A study of wet coffee fermentation in Thailand identified yeasts and lactic acid bacteria among the predominant groups associated with measured flavour and aroma compounds. Those observations help explain why fermentation is studied as part of coffee quality; they do not give every naturally fermented lot the same flavour.
For a useful comparison, keep the lot identity and processing description with the tasting notes.
Spontaneous fermentation
When a producer relies on the existing microbial community rather than adding a selected starter, the process is described as spontaneous fermentation. The community and its activity depend on the coffee and processing conditions.
A study of wet coffee fermentation in Thailand identified yeasts and lactic acid bacteria among the predominant groups associated with measured flavour and aroma compounds. Those observations help explain why fermentation is studied as part of coffee quality; they do not give every naturally fermented lot the same flavour.
For a useful comparison, keep the lot identity and processing description with the tasting notes.
What microorganisms are added during coffee fermentation?
Some producers add a selected microbial starter culture during fermentation. The aim is to influence the microbial community and the compounds produced during the process.
The name of a microorganism alone does not describe the complete method. Ask which culture was used, how the producer describes the process and which lot the information belongs to.
What research can show
A study comparing starter-inoculated and spontaneous wet fermentation measured differences in the microbial communities, metabolites and sensory attributes of the Arabica coffees tested. Lactic acid bacteria and Kazachstania yeasts were among the groups linked to metabolites in the inoculated process. The inoculated samples received more favourable sensory descriptions in that comparison.
That result concerns those samples and conditions. It is a reason to examine the process and taste the lot, rather than treat the addition of a culture as a guaranteed quality score.
The name of a microorganism alone does not describe the complete method. Ask which culture was used, how the producer describes the process and which lot the information belongs to.
What research can show
A study comparing starter-inoculated and spontaneous wet fermentation measured differences in the microbial communities, metabolites and sensory attributes of the Arabica coffees tested. Lactic acid bacteria and Kazachstania yeasts were among the groups linked to metabolites in the inoculated process. The inoculated samples received more favourable sensory descriptions in that comparison.
That result concerns those samples and conditions. It is a reason to examine the process and taste the lot, rather than treat the addition of a culture as a guaranteed quality score.
Descriptions such as lactic fermentation refer to the microbial activity or processing approach, but the description alone does not specify the finished coffee’s sweetness, acidity or fruit notes.
Compare the actual lot
Ask for the coffee’s origin, lot reference, processing description and available sample. Keep those details together when comparing quotations.
Taste samples with a consistent roast and preparation where practical, and record the aroma, flavour and texture you actually perceive. If the supplier provides a cupping score, ask which sample and assessment it refers to.
For a later order, confirm that the quoted product matches the sample reference. A clear lot description and repeatable tasting are more useful buying evidence than a fermentation label on its own.
Compare the actual lot
Ask for the coffee’s origin, lot reference, processing description and available sample. Keep those details together when comparing quotations.
Taste samples with a consistent roast and preparation where practical, and record the aroma, flavour and texture you actually perceive. If the supplier provides a cupping score, ask which sample and assessment it refers to.
For a later order, confirm that the quoted product matches the sample reference. A clear lot description and repeatable tasting are more useful buying evidence than a fermentation label on its own.
Discuss Fermentation Details With a Supplier
When discussing a particular process with a supplier, ask which exact coffee and sample the description refers to. Keep the product reference with your tasting notes and intended preparation method.
Record the process request, sample, pack size and commercial details in the coffee wholesale RFQ worksheet before comparing offers.
Send the wholesale team your coffee format, destination and expected order size.
Record the process request, sample, pack size and commercial details in the coffee wholesale RFQ worksheet before comparing offers.
Send the wholesale team your coffee format, destination and expected order size.
27.08.2021