Identification of unique chemical fingerprint ensures that buyers are getting what they pay for


Coffee beans digested by the Asian palm civet supposedly make for better coffee

Scientists in Japan have developed the first standardised test to authenticate the world’s most expensive coffee. Kopi Luwak, Indonesian for civet coffee, is produced from coffee beans retrieved from the faeces of the Asian palm civet, a cat-like mammal from which the coffee inherits its name. The team found that the digestion process left a unique chemical fingerprint that sets Kopi Luwak apart from other coffees and may also be responsible for its distinctive taste.

Civet coffee retails at up to $227 (£145) per pound, but such a high market value makes it a target for fraud where regular coffee is often packaged and sold as Kopi Luwak or real Kopi Luwak is mixed with cheap beans. To ensure buyers get what they pay for, the Indonesian Coffee and Cocoa Research Institute teamed up with the scientists at Osaka University, Japan, and came up with an authentication procedure based on metabolomics – the study of unique chemical markers produced by specific cellular processes.

‘Although there were previous reports about discrimination of Kopi Luwak and regular coffee using an electronic nose, we are the first to report the metabolites responsible for the differences,’ explains team member Sastia Putri.


The beans excreted by the civet are collected and processed into the world's most expensive coffee

Fundamental to this procedure is GC-MS with high enough sensitivity to detect a large number of metabolites. Coupled with mulitvariant analysis, the researchers were able to select the most significant discriminant markers from 21 different coffee samples. What they found was that Kopi Luwak contained higher proportions of citric acid and malic acid thought to be a result of the digestive process. ‘These markers were able to differentiate pure Kopi Luwak, mixed coffee, a 50:50 mix of Kopi Luwak and regular coffee blend, and regular coffee,’ Putri says.

According to Nikolai Kuhnert at Jacobs University, Germany, this work reflects the recent popularity of GC-MS in medical research and food chemistry. ‘It has been applied on numerous occasions for food discrimination and authentication,’ he explains, but in general ‘methods identify compounds that are present in higher or lower amounts, which makes distinction not as clear-cut’ by comparison.

Putri believes that by extending the method to include several more markers they will better understand the many more metabolite changes that occur after digestion by the luwak that make the coffee so unique. ‘We are hoping that we can expand this method for quality assessment of Kopi Luwak and also to determine the key metabolites that contribute to the unique flavour and aroma of Kopi Luwak.’