The civet’s diet in coffee-forest habitats includes over 55 food items, with coffee berries constituting most of their biomass9 (Habtamu et al., 2017), alongside seeds from other plants like palm10.
Coffee bean comprises various components, including carbohydrates, proteins, and phenolic compounds derived from caffeine, ferulic acids, lipids, tannins, and minerals, contributing to their overall chemical composition and influencing flavour and aroma in coffee beverages42. The correlation of these parameters can be instrumental in conducting comparative studies with ecological parameters because these factors relate with eco-chemical relationships43.
Among the macro-nutrients, the total fat content shows a significant difference, where the civet sample has a significantly higher fat value than the manually collected samples. Fat contributes significantly to coffee’s aroma and taste profile, which presumably plays a significant role in determining the flavour characteristics supporting the findings5. Regarding the other parameters, there is no statistically significant difference between the two categories. For instance, the pH value slightly increases in the manually collected samples compared to the civet scat samples. However, both fall within the normal pH range of standard consumable coffee. The fermentation process in civets contributes to the distinct taste of kopi luwak, with studies showing that metabolites in civet coffee differ significantly from regular coffee18. This is supported by the total acid content, which is also slightly higher in the manually collected beans. This indicates that the digestion framework and chemical mechanisms inside the animal’s gut may be responsible for these differences.
Furthermore, the volatile metabolomics fingerprint of coffee beans varies significantly between different types and origins44. The higher fat content in civet coffee may contribute to a unique volatile profile, affecting its aroma and flavour. This is supported by research by Endeshaw and Belay45 showing that roasting conditions and processing methods can significantly impact coffee’s volatile compounds and sensory characteristics.
Total protein and caffeine content are also slightly higher in the manually collected samples than in the civet samples. The lower level of proteins due to proteolysis leading to shorter peptides and amino acids would contribute to the decreased bitterness of civet coffee19. Civet coffee exhibits higher antioxidant properties and unique amino acid profiles linked to its sensory characteristics and market value46. Reports suggest such findings exist, and our study also shows similar results regarding caffeine and protein content. Presumably, a possibility behind the increased levels of caffeine and total protein content could also be a supplement to the cured extraction procedures undergone during chemical analysis. Alongside fat, the total reducing sugar content in civet samples is also recorded to be slightly higher than in the manually collected samples, though not significantly so.
Few reports5,19,44,47 elaborate on the chemical characteristics of Luwak coffee. The bio-processing within the gastrointestinal tract results in the reduction of caffeine content in Robusta Luwak and Arabica Luwak coffees. There is also the formation of characteristic odour due to digestion. Roasting reduces the amount of caffeine by a negligible percentage. Besides caffeine, the protein level48 was also determined to be low, which signifies that the proteins were partially degraded and diffused out in the gastrointestinal tract of the animal during digestion. It has some evidence that the fermentation in the gastrointestinal tract of civet enhanced its quality due to the optimal temperature. Apart from that, it is also helped by the bacteria found in the intestinal system and coffee bean proteins are broken down by proteolytic enzyme in the intestine. This results in short peptides and free amino acids that gives Luwak coffee a special flavour. After processing, in gastrointestinal tract, there is higher lipid content of coffee in comparison to original coffee that is associated with higher lipid content contributes to tasty taste.
Notably, some of the compounds like palmitic acid ethyl ester, methyl-13-octadecenoate, 8,11-octadecanoic acid methyl ester, 16-octadecanoic acid methyl ester, and 9,12-octadecadienoic acid were found in minimal or undetectable quantities in the civet samples in our study. The volatile compound composition of coffee can be controlled by numerous factors such as coffee variety, geographic origin, and processing44,49,50. In particular, fermentation during coffee processing controls the volatile compound composition, which enhances specific flavour characteristics. This suggests that the unique digestive process of the Asian palm civet may play a role in altering the volatile compound profile of civet coffee.
Among the six fatty acid methyl esters, caprylic acid methyl ester and capric acid methyl ester were significantly higher. These two fatty acid compounds are instrumental as flavouring and aroma agents in food, often imparting a dairy or milk-like aroma and flavour. The etymology of “capric” derives from the Greek term for goat (“Capra”). Both compounds are traditionally used as flavouring agents in certain dairy-based products and as antimicrobial agents. The significant difference in these two compounds between the sample types presumably contributes to the unique taste profile of civet coffee beans, supporting claims that civet coffee possesses a distinctive flavour compared to conventional varieties mainly supported by the fermentation procedure enhancing flavour profiles20, and also justifying our finding of a significantly higher fat level in the civet variety. FAME profiling of civet coffee reported similar findings to the studies conducted by Ifmalinda et al.5 While such differences may suggest potential implications for flavour, it is noteworthy that the roasting process substantially alters lipid composition, as many fatty acids degrade into other compounds that may contribute indirectly. During the roasting procedure, various physical and chemical changes typically occur, involving the Maillard reaction, caramelization, and lipid oxidation, as noted by Adadi et al.25 The Maillard reaction leads to the formation of melanoidins, imparting the brown colour and rich flavours to the coffee. At higher temperatures, monosaccharides form furans and caramels, enhancing the complexity of roasted coffee. The extent of roasting imparts distinctive colour. Lipid oxidation breakdown, significantly impacts coffee’s aroma. In this regard, our study aims to keep the native parameters intact by examining the raw levels of these compounds without being hindered by the process of roasting. Therefore, variations in fatty acid content in raw beans should be interpreted cautiously and not directly equated with differences in the flavour of the final roasted coffee. This is consistent with the broader understanding that coffee flavour is largely generated during roasting, when a range of volatile, flavour-active compounds are formed. The representative chromatograms support the variations observed in the quantities of volatile and semi-volatile compounds and fatty acid methyl ester levels, as depicted by differences in peak intensities across the samples. These results are interpreted from the percentage area covered by each compound, as indicated by their corresponding peaks. Research has indicated that controlled fermentation can change metabolite content and enhance coffee flavour quality51. Passing through the digestive system of the civet is a type of natural fermentation that increases the complexity of the flavour.
Research by Watanabe et al.29 found that the genus Gluconobacter is exclusively present in faces and gut microbiomes of civet cats. Gluconobacter contains an over-representation of genes that code for enzymes to metabolize hydrogen sulphide and sulphur-containing amino acids. These enzymes play a crucial role mainly in the fermentation processes of the civet’s digestive tract, and they may impact the flavour of kopi luwak. The degradation of structural polysaccharides facilitates the penetration of fermented metabolites into coffee beans. The availability of amino acid fermentation residues adds to the coffee sensory notes and adds to the enhanced aroma. The fermentation processes facilitated by the unique microbiome of the civet cat are proposed to contribute to the distinctively smooth flavour of civet coffee. This aspect highlights the biological basis for the unique characteristics of this expensive coffee.
Among the 37 parameters, some compounds, including some volatile compounds and fatty acids, were absent in detectable quantities in the organic farm samples. The absence of these compounds in organic farm samples may be attributed to the specific maintenance techniques applied in organic farming. The application of certain manures, enhancers, or treatments in conventionally managed farms results in the presence of these compounds at comparatively higher levels53. However, a study with a more extensive sampling across multiple organic farms could be necessary to reach a definitive conclusion.
From their appearance, the civet samples and the manually collected ones show slight differences in texture. The civet samples have a comparatively rougher surface and silver skin. They are presumably darker in shade than the manually collected Robusta beans, which have a comparatively smoother surface texture and are slightly lighter in shade. Moreover, study shows that civet coffee bean samples have lower absorbance values in visible spectra than non-civet coffee bean samples, as determined by visible spectroscopy53. Though shade and colour are subjective and vary across samples, our observation suggests that civet samples are rough due to their passage through the gut and the digestive process encountered within the animal.
Elaborating on the morphometry of the coffee beans, the mean length and width of civet samples are notably higher than those of manually collected coffee beans. These observations can be linked to the selective fruit consumption by the civet, which prefers fruits of larger dimensions and greater ripeness—those with more flesh—since the animal is primarily concerned with flesh intake from the fruit. This supports the morphometric data from our study. Study shows that specific physicochemical parameters, including density and acidity, correlate with bean dimensions, affecting overall quality perception54.
The decrease in dimension of berries in organic coffee can be justified by the controlled use of fertilizers and enhancers in organic farms, compared to conventional farms where the standard application of such substances boosts bean dimensions to improve yield and production. Beans from organic farms were comparatively more minor in dimension. Applying inorganic fertilizers resulted in taller coffee plants, which may correlate with larger bean size, as observed in studies where inorganic treatments produced higher yields52. Research by Severa et al.24 cites that the quality of coffee beans depends on size and shape, where there are definite correlations between length, width, depth, and their coefficients of variation, adding to knowledge of coffee quality factors.
The manually collected beans showed a slightly higher mean weight in contrast to the civet samples. This can be assessed from studies indicating that digestion and fermentation of coffee beans inside the civet’s gut may contribute to the absorption and breakdown of specific bean properties, which could be linked to the observed overall decrease in weight in scat samples.
The fermentation process can also influence the moisture content and weight of the beans, potentially leading to variations in market value22,55. Regarding management type, beans from organically managed farms had slightly lower weight than those from conventionally managed farms. This supports the claim that fewer enhancers and pesticides in organic farming may result in smaller bean sizes, unlike conventional farms where artificial enhancers are commonly used. Studies on this by Tran et al.56 claim that there exists no strong correlation between bean morphology and levels of non-volatile or volatile compounds, indicating that selecting specific biochemical traits based on the physical characteristics of coffee beans is challenging. However, more researchers like Torres et al.57 claim that dimensions such as length, width, and depth of coffee beans significantly affect their mechanical properties, including firmness and fracture energy. In that regard, our findings validate them. Even organic practices can enhance specific quality attributes of coffee beans, while conventional methods may yield higher overall productivity. A study by Xu et al.58 reveals that intensive organic management significantly increased mineral contents, total lipids, and fatty acids compared to moderate conventional practices.
Ex-vivo treatment with an acidic solution containing specific enzymes such as amylases, glucosidases, mannosidases, dextranases, proteases (including exo and endoproteases), phosphatases, phytases, phospholipases, lipases, and nucleases and specifically the enzyme pepsin, particularly porcine pepsin for a duration of approximately 90 min–24 h – might result in production of enhanced Coffee Aroma similar to civet coffee59.
Health benefits of coffee are increasingly supported by scientific studies. Higdon and Frei60 noted that moderate coffee consumption may reduce the risk of chronic diseases such as type 2 diabetes, with minimal health risks for most adults. However, Jeewan et al.61 pointed out a lack of long-term studies on health impacts and environmental consequences of coffee production.