Comprehensive characterization of bioprocessed exotic coffees: volatile compounds, their precursors and descriptive sensory analysis

Abstract

Exotic coffees may be defined as extravagant and unique, mostly due to their superior sensorial characteristics, rarity, exclusiveness and high selling prices. Kopi Luwak coffee beans are bioprocessed by the Asian palm civet (Paradoxurus hermaphroditus), and Jacu coffee by the bird Jacu (Penelope superciliares). Then, beans are collected, cleaned, and undergo the usual steps of dry or wet post-harvest processing and roasting. We investigated the effect of bioprocessing, growing conditions and roasting on the chemical composition and sensory profiles of Jacu and Kopi Luwak coffees. The effect of bioprocessing on aroma precursors and flavor compounds was evaluated for the first time for Jacu coffee. Scanning Electron Microscopy results strongly suggested that Jacu and Kopi Luwak green coffee beans were bioprocessed. For the first time in the literature, lipids and amino acids compositions, sucrose and volatile compounds such as methyl heptanoate, methyl decanoate, methyl stearate, 4-acetoxymethyl-2-furaldehyde and 5 acetoxymethyl-2-furandehyde were described for Jacu and Kopi Luwak coffees. Furans and furanones were considered chemical markers of green Kopi Luwak coffee growing conditions. Sweetness, cleanliness and uniformity presented the higher scores in all coffee samples. The digestion process by the Jacu bird modified profiles of caffeine, CGA, TAG and amino acids, as well as aroma compounds. The weather conditions related to each crop year of Kopi Luwak coffees affected the flavor precursors composition and sensory profiles. However, it was not possible to identify which specific climatic conditions led to this difference between the crops. All these changes affected the formation of volatile compounds upon roasting, thus contributing to the unique flavor and aroma of these exotic coffees.