Co-fermentation and infusion: what goes into the bean
What happens when an ingredient is added?
Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.
An inventory published in early 2023 lists fruits, apple, grape, strawberry, orange, local berries; organic or mineral acids, citric, malic, tartaric and as far as phosphoric; hops; spices; and mosto, the juice or the recycled pulp of coffee.
Read the stages without animation
- What goes into the tanksAn inventory published in early 2023 lists fruits, apple, grape, strawberry, orange, local berries; organic or mineral acids, citric, malic, tartaric and as far as phosphoric; hops; spices; and mosto, the juice or the recycled pulp of coffee.
- Citric acid favors lactic bacteriaThe most invoked mechanism is indirect: citric acid lowers the pH and favors lactic acid bacteria.
- Aromas get into the beanAt CIRAD, Fatma Hadj Salem put labeled aroma compounds into the liquid medium, then looked for them in the bean. 2-phenylethanol, isoamyl acetate and butanal get through, the first with the highest transfer rate; the brakes are the resistance of the parchment, adsorption on the walls of the yeasts and degradation reactions in the bean. The watertight-parchment argument is false.
- Where the line is drawnThe Cup of Excellence tolerates no addition other than water but admits yeasts and mosto; the SCA has banned, since late 2023, any additive after the green coffee stage; the Best of Panama disqualified four infused coffees in 2024. Chromatography and isotope measurement can spot a foreign aroma; a standard is missing.
To remember: Something does get into the bean; the point of agreement is labeling, not legitimacy.
Read the full article and its sources ↓An inventory published in early 2023 lists what is put in the tanks: fruits, apple, grape, strawberry, orange, local berries; organic or mineral acids, citric, malic, tartaric and even phosphoric; hops; spices, ginger, aji chili, cinnamon; and mosto, juice or pulp of recycled coffee. The most frequently invoked mechanism is indirect: citric acid lowers the pH and favors lactic acid bacteria.
The thorny question is whether what is put in the tank reaches the bean. The work of Fatma Hadj Salem at CIRAD (Qualisud, Institut Agro Montpellier, a thesis with a yeast manufacturer) settled it: labeled aroma compounds are put in the liquid medium and then searched for in the bean. 2-phenylethanol, isoamyl acetate and butanal pass through, the first with the highest transfer rate; the identified limits are the resistance of the parchment, adsorption on yeast walls and degradation reactions in the bean.
Something does get into the bean; the argument of the watertight parchment is false. This does not say whether that is good or bad, nor whether the quantities transferred explain the spectacular profiles of some lots.
Roast Magazine no. 115, January-February 2023; Hadj Salem et al., Food Chemistry (2020) and Journal of Food Engineering (2022), solid level; LC ch. 17b| Body | Position | Year |
|---|---|---|
| Cup of Excellence | Zero tolerance for foreign ingredients, no additive other than water; yeast inoculation and mosto allowed; “Experimental” category created in Brazil | 2023 |
| SCA, world championships | Old rule: no additive between the cherry and the beverage. New rule: no additive after the green coffee stage, so co-fermentation is allowed if the addition comes before the green stage | late 2023, WBC 2024 |
| Best of Panama | Four infused coffees disqualified, judged to have been altered by foreign additives with the intention of scoring better | 2024 |
Three bodies, three lines, the same year. Individual positions are just as scattered: Šestić, who introduced carbonic maceration, criticizes the lack of transparency ' '; Kyle Ramage speaks of a slippery slope; Jorge Hernán Castro Molina considers that the practice harms specialty coffee when labeling is lacking; on the other side, Christopher Feran and Edwin Noreña defend microbial modulation as a legitimate tool. The opponents do not say that it is bad, they say that it is not declared; the supporters do not ask for the right to deceive, they ask for the right to use a tool. The point of agreement is labeling, not legitimacy, and the control tool exists: gas chromatography coupled with mass spectrometry (GC-MS/MS) and measurement of isotope ratios (GC/C/IRMS) identify exogenous aromas. What is missing is a standard to anchor it to.
Trade press 2023-2024; LC ch. 17b