The unique flavor of the luxury coffee favored by Hollywood stars and influencers, "kopi luwak," has been found to be a collaboration between the fat in coffee beans and gut bacteria.
A team led by Palatty Allesh Sinu, a professor in the Department of Zoology at Central University of Kerala in India, said it compared coffee cherries collected from civet droppings with regular coffee cherries harvested by people and found that civet coffee contained more fat and was rich in certain aromatic compounds. The findings were published on Jan. 24 in Scientific Reports.
Kopi luwak is made by collecting beans from the excrement of Asian palm civets that have eaten ripe coffee cherries. The pulp is digested, but the seeds, or green beans, pass through the intestine and are excreted. Coffee made by roasting these beans sells for more than $1,000 (about 1.4 million won) per kilogram.
Scientists have long debated how the civet's digestive process changes the aroma and taste of coffee. To answer that question, the team collected 68 samples of droppings from wild civets at a coffee farm in Karnataka in southern India on Jan. 1, along with Robusta cherries harvested directly from coffee trees in the same area.
Civets are nocturnal animals that like tropical fruit. According to the team, 85% of the collected droppings were piled in elevated spots such as on tree stumps or logs. The team explained that this is due to the civet's defecation habit of using specific spots like a toilet.
The team washed the droppings and ground the beans obtained to analyze their components. They examined basic nutrients such as protein, caffeine, sugars, and fat, as well as trace chemicals that determine flavor.
For flavor analysis, they used gas chromatography–mass spectrometry (GC-MS). The instrument can separate hundreds of trace compounds in a sample and identify the characteristics of each. The team closely compared the composition of volatile and semi-volatile aroma compounds and fatty acid methyl esters, and also measured the length, width, and weight of the beans.
The analysis found that beans that had passed through the civet's digestive process had higher fat content than regular beans. In particular, concentrations of the fatty acid compounds methyl caprylate and methyl caprate, which influence aroma and mouthfeel, were markedly higher. The two substances are known to impart soft, creamy, and nutty flavors like milk or cream.
The team said these compounds may have contributed to the characteristic smooth, deep taste of kopi luwak. Because fat acts as a medium through which aromatic compounds diffuse, a higher fat content can make coffee aroma richer.
This study is a rare case of scientifically identifying the chemical origins of coffee aroma and taste. The team said, "It appears that gut microbes and enzymes in the civet induced natural fermentation in the beans, altering their chemical composition."
However, the study is limited by comparing against unroasted Robusta beans. Most kopi luwak sold on the market is Arabica. The team added, "Further research is needed to determine how the fat components that have undergone digestion translate into flavor after roasting the beans."
References
Scientific Reports (2025), DOI: https://doi.org/10.1038/s41598-025-21545-x