In this study, L-leucine powder (LP) was added on the Robusta green beans in two ways to reduce the bitter aroma (phenols, pyrroles and pyrazines). In the method I, green coffee beans (<i>Coffea robusta</i> produced in Vietnam) were soaked in filtered water for 1 min, and then mixed LP (0.1, 0.5, 1, 2 and 3% (w/w)). According to the method II, green coffee beans were sprayed with filtered water and mixed with LP (1 and 3% (w/w)). All green beans were roasted at 240 °C for 15 min and extracted using espresso machine. Volatile compounds were analyzed by solid phase microextraction (SPME)-GC-MSD. The selected 30 volatile compounds including 6 pyrroles, 8 pyrazines, 3 phenols, 9 furans, 2 ketones and 2 aldehydes were analyzed.<br/>In 15 coffee samples, levels of total volatile compounds (peak area ratio of total aroma compounds and internal standard) were ranged from 8.908 (M1-1 sample) to 15.469 (non-treated Robusta coffee: NTR). The sum of bitter volatiles (phenols, pyrroles and pyrazines) in M1-5 sample (3% LP, dried at 50 °C for 15 min) were lower than that of NTR by 24.6% (p&lt;0.05). The sum of bitter volatiles in M2-1 sample (1% LP, dried at 50 °C for 15 min) were lower than that of NTR by 38.07% (p&lt;0.05). In particular, the levels of pyrroles and pyrazines in M2-1 sample lower than those of NTR by 49.1 and 49.5%, respectively (p&lt;0.05). A M2-7 sample (3% LP, dried at 70 °C for 15 min) has 43% lower levels of pyrazines and 18.4% lower levels of bitter aroma than those of NTR. Robusta coffee prepared with LP has lower bitter aroma than Robusta coffee and, especially, M1-5, M2-1 and M2-7 have the lowest bitter volatiles among Robusta coffee prepared by LP.

Improvement of the Robusta coffee aroma by adding L-leucine powder on the green coffee beans

ACS Fall 2021

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