Chromatography has replaced the microscope. It separates the molecules of an extract instead of looking at shapes, and so sees what a roasted powder no longer shows. The review by Martins and colleagues (2018) reports on the Brazilian domestic market adulterations reaching 40% by weight of corn, soy, barley, rye, caramel and husks.

The same work draws up the map of markers, because spotting a filler is not enough: to accuse it, it must be named. Each added ingredient brings a molecule that gives it away.

• Glucose, mannose and fructosecereals and husks.
• Maltosecorn.
• Raffinose and stachyosesoy.
• Gamma-tocopherolcorn again, outside the register of sugars.
• 5-hydroxymethylfurfuralchicory.
• 16-O-methylcafestol and homostachydrinecanephora.
• The chlorogenic acids and the volatile pyrazinesthe origin of the lot.

Each family then has its own assay. Carbohydrates go through HPLC, that is, high-performance liquid chromatography, with amperometric detection and standard ISO 11292 as the framework. The limits there are 1 to 2.5 ppm, a part per million being one milligram per kilo. Headspace GC-MS, which analyzes the air loaded with volatile compounds above the heated sample, detects barley from 1%. UPLC-MS, for its part, brings the analysis down to 15 minutes against 72.6: nearly five times more samples checked for the same laboratory time.

16-O-methylcafestol, the 16-OMC of the laboratories, is assayed separately, by high-performance thin-layer chromatography. Detection goes down to 5 mg/kg and quantification to 20 mg/kg, that is, less than 0.9% canephora in the packet. Above all, the marker survives roasting and the making of instant coffee. That is what makes it useful, because species fraud hides precisely there, in ground coffee and in instant coffee, where nobody sees the bean anymore.

Martins et al., Food Quality and Safety, 2018, academic.oup.com/fqs/article/2/3/121/5041966; pubmed.ncbi.nlm.nih.gov/29042111 (J. Chromatogr. A, 2017); contractlaboratory.com, April 3, 2026

NMR has become the sieve of control laboratories. Nuclear magnetic resonance places the extract in a magnet and reads the signature each molecule leaves there. The Norwich method runs on a benchtop magnet at 60 MHz, a device that fits on a table, in 40 minutes per extract.

With ten times the field, one sees ten times finer. At 600 MHz, Milani and colleagues (Food Control, 2020) classify adulterated coffees with 100% success. The fillers tested were barley, corn, husks, soy, rice and wheat. The starch signal serves as a marker, since it is the added cereals that bring it. Detection limits come down to between 0.31 and 0.86% in medium and dark roasts.

Near infrared, for its part, does the bulk sorting. The powder is illuminated, the light it sends back is read, with no reagent or preparation, hence no consumable for each measurement. Couto and colleagues (Foods, 2021) thus tell pure from adulterated from 0.25% on corn, barley, soy, rice, husks and canephora. But they identify the adulterant only beyond 10%, and not beyond two mixed together: the method sees that there is something, it does not say what.

Zhang and colleagues (Foods, 2025) took the device out of the laboratory. Their portable spectrometer scans from 900 to 1,700 nm. It obtains 96.9% correct answers in qualitative mode and 92.3% in quantitative mode, on soy, barley, chicory and corn at 10 to 40%. A scan lasts 2.54 milliseconds. But the model was built on a single reference arabica, which says nothing about how it holds up on others.

NIR therefore remains a screen, not proof. Its positives must be confirmed by reference chemistry.

Bruker, application note NMR in the Detection of Coffee Adulteration, citing Milani et al., Food Control 2020; Couto et al., Foods 2021, PMC8750839; Zhang et al., Foods 2025, PMC11817766

For origin, no single marker exists. Stable isotopes record the place: in Hawaii, Rodrigues and colleagues (2011) measured on 47 green arabicas from five regions the δ18O, higher at low altitude and linked to rain, the δ34S, depleted near active volcanoes, the δ13C and the δ15N, and the 87Sr/86Sr ratio, lower near volcanoes and higher near coasts; isotopes alone do not separate the five regions, the combination with multi-element analysis manages it, and the authors call for several years of sampling.

Detection: from yesterday to today

Thurber 1881, p. 167-168; Walsh 1894, p. 216-221; Ukers 1922, ch. XVI-XVII; Martins et al. 2018; Gunning et al. 2018; Milani et al. 2020 (Bruker); Couto et al. 2021; Zhang et al. 2025; Rodrigues et al. 2011; contractlaboratory.com 2026

DNA identifies the species and certain varieties by PCR or digital PCR when roasting has degraded 16-OMC, but roasting also fragments the DNA. GC-MS metabolomics supplied the markers of kopi luwak. None of these methods answers the question of the 19th century, which remains whole: that of the cost of control relative to the price of the goods, and of who pays for it.

Rodrigues et al., J. Agric. Food Chem., 2011, PMC3256934; contractlaboratory.com, April 3, 2026; en.wikipedia.org/wiki/Kopi_luwak