References: The secret is sulphur

References for article (Issue 5 2020) in which Erich Leitner and Bernhard Ringer explain importance of sulphur compounds in roasted coffee.


Flavour description





extremely diffusive, repulsive, reminiscent of wild radish, sharp, green, cabbage like; in high dilution bearable, almost acceptable, pleasant, vegetable like


vary between 0.3 and 60.0 ppb; 1 ppb and 0. 33 ppb

0.5-3.5 in roasted coffee and 0.1-3.5 ppm in green coffee (Rhoades 1960); 0.1-0.2 ppm in healthy roasted arabica but 0.8-1.0 ppm in one having a stinking quality by Guyot and Vincent (1990)



intensive onion-like character


3 ppb to 7.6 ppb in water and 12 ppb

0.01 ppm in arabicas and 0.10-0.12 ppm in Robustas by Silwar et al. (1986) 0.04-0.05 ppm in a roasted healthy arabica and 0.3 – 0.4 in the stinking quality by Guyot and Vincent (1990)



powerful, diffusive, penetrating odour of fresh onion, cabbage, burnt, cooked

0.01 ppb


1 ppb in two arabicas and 0.1 ppm in two other arabicas by Silwar et al 1986



Rotten cabbage; one of the most intense noted to roasted coffee

0,02 – 2.1 ppb in water

1.5-4.3 in roasted coffee and 0.1-0.3 ppm in green coffee by Rhoades 1960



pure substance smells pungent or leek like; at 0.1 ppm penetrating animal like, foxy, skunky; at 0.4 ppm skunky, meaty, coffee, fatty, tarry

0.2-0.4 g/m^3 in air and 0.2 – 0.3 ppt (0.0002-0.0003 µg/L) in water

8.2 ppb in freshly roasted ground coffee by Grosch (1996)




classic coffee odor, extremely powerful, diffusive penetration odor, in proper dilution gives coffee-like, caramel-like-burnt, sweet


0.04ppb down to 5 ppt


1.1 ppm in arabica and 2.0 ppm in Robusta by Tressl and Silwar 1981, similar from Silwar 1986 and Tressl 1989; 1.7 ppm in a Columbian arabica by Grosch et al 1993 and 1.95 ppm in an Indonesian Robusta; 1.08 ppm for an arabica and 1.73 ppm for a Robusta by Semmelroch et al 1995




meat like, roasted coffee


0.005-0.01 ppb


0.148 ppm in a Columbia arabica and 0.195 in a Kenya arabica by Grosch et al 1996




powerful, diffusive onion and meat like, in dilution more pleasant, less onion-like, reminiscent of bouillon; at 2 ppm typical meaty and sulfur flavor


0.2 ppb in water; and 9 µg/kg in cellulose


240 ppb in Columbian arabica and 95 ppb in an Indonesia Robusta  Semmelroch et al. 1995 ; 22 ppb in green arabica and 213 ppb after roasting Czerny and Grosch 2000


sweaty, fruity odor, becoming black currant and catty in aqueous solution at 0. 1 ppm; penetrating sweaty and catty; belong to the most potent odors; at 0.1 ppm tropical, fruit, green, sulfur, hop flavor and black currant, leaves, clary sage and orange flowers; in great dilution in a coffee beverage roast coffee likeness


2-5 ppt odor thresholds and 5-8 ppt taste threshold; 3 * 10-4 µg/m3 in air and 3.5 ppt in water

0.13 ppm in arabica and 0.115 ppm in Robusta by Semmelroch et al 1995

The most important sulphur compounds, their odour thresholds and concentrations in coffee.

Credit: Flament, Ivon; Bessière-Thomas, Yvonne (2002): Coffee flavor chemistry. Chichester, New York: Wiley

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