Mineral composition and antioxidant activity of partially digested coffee “Kopi Luwak”

Background: Kopi Luwak is a rare type of coffee, that is partially digested in the Asian palm civet’s digestive tract before roasting. It therefore possesses a distinctive flavor and unique properties, shaped by the digestive enzymes in the civet's intestine. Objective: In this study, the differences of mineral composition, antioxidant potency and total polyphenol amount between commercially available Kopi Luwak and regular coffees (without digestive fermentation) were evaluated. Methods: Twenty-one regular type of coffee bean and 17 of Kopi Luwak bean were purchased from local markets or Kopi Luwak production company in Indonesia. The samples were then analyzed for the levels of 23 minerals (Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, Li, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sn, Sr, V and Zn) using ICP-MS system. The total polyphenol amount and antioxidant activity were evaluated using Folin-Ciocalteu assay and DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging assay, respectively. Results: Of these 23 minerals, the concentrations of Mn and Ba were significantly lower in Kopi Luwak than in regular coffee. Otherwise, the concentrations of Cu and Rb in Kopi Luwak were significantly higher than those in regular coffee. The IC50 value on DPPH radical scavenging assay of Kopi Luwak (61.4±2.8 mg/dL) was significantly lower than that of regular coffee (93.6±1.9 mg/dL). Total polyphenol amount for Kopi Luwak was significantly higher than regular coffee. The correlation factor between these factors was r = -0.5910 and p < 0.001. Conclusion: Kopi Luwak had lower concentrations of Mn and Ba, but higher levels of Cu and Rb compared to regular coffee. Additionally, Kopi Luwak exerted strong antioxidant activity and contained higher polyphenol amounts than regular coffee. Thus, our findings imply that Kopi Luwak is an important candidate for functional foods. Keywords: antioxidant potency, ICP-MS, Kopi Luwak, mineral composition, polyphenols