Improvement of Robusta coffee aroma with l‐leucine powder

Abstract

L-leucine powder (LP) were added to improve the aroma of Robusta coffee beans. Treatment was a short soaking (M1) or spraying procedure (M2), then LP was added at varying levels up to 3% (w/w). All samples were roasted (240 °C/15 min) and extracted using an espresso machine. Volatile compounds were analysed by solid-phase microextraction−gas chromatography−mass selective detection. Thirty volatile compounds (6 pyrroles, 8 pyrazines, 3 phenols, 9 furans, 2 ketones, 2 aldehydes) were analysed. In 15 coffee samples, the levels of total volatile compounds (based on peak area ratios) ranged from 8.9 (M1-1) to 15.5 (non-treated Robusta: NTR). Robusta coffee has lower levels of bitter aroma compounds when pre-treated with LP. The sum of bitter volatiles (phenols, pyrroles, pyrazines) was lowest in M1-5 (3% LP), M2-1 (1% LP; both dried at 50 °C/15 min) and M2-7 (3% LP, dried at 70 °C/15 min) compared with NTR (p < 0.05). NTA 5.02±0.01 a 33.17±0.01 a 14.50±0.05 f 27.74±0.05 a 45.61±0.03 a M1-1 5.28±0.01 c 37.55±0.01 c 13.73±0.04 d 30.04±0.02 c 50.01±0.02 c M1-2 5.28±0.01 c 38.46±0.00 e 13.63±0.04 c 30.80±0.03 d 51.13±0.03 e M1-3 5.31±0.01 e 40.70±0.09 f 13.35±0.04 a 31.59±0.13 f 53.22±0.15 g M1-4 5.30±0.01 d 37.17±0.00 b 13.71±0.04 d 29.92±0.00 b 49.65±0.01 b M1-5 5.27±0.01 b 38.39±0.00 d 13.89±0.04 e 31.02±0.03 e 51.28±0.02 f M2-1 5.28±0.01 b 39.85±0.02 j 13.64±0.04 c 31.44±0.07 g 52.56±0.04 i M2-2 5.33±0.01 e 37.15±0.00 e 13.63±0.00 b,c 29.67±0.03 c 49.46±0.02 d M2-3 5.30±0.00 c 35.37±0.01 c 13.62±0.05 b,c 28.65±0.03 b 47.52±0.01 b M2-4 5.32±0.01 d 39.04±0.01 i 13.48±0.04 a 30.63±0.02 f 51.42±0.01 h M2-5 5.33±0.01 e 37.46±0.00 f 13.91±0.04 e 30.41±0.03 e 50.21±0.02 e M2-6 5.32±0.01 d 35.31±0.01 b 13.72±0.05 d 28.68±0.02 b 47.52±0.01 b M2-7 5.28±0.01 b 38.07±0.01 g 13.72±0.05 d 30.56±0.05 f 50.71±0.02 g M2-8 5.31±0.01 c 35.51±0.01 d 13.57±0.05 b 28.70±0.02 b 47.64±0.01 cAll levels are represented as mean ± standard deviation (S.D.) (n=3) (p<0.05).

Effect of organic acid-soaking and sonication on the formation of volatile compounds and α-dicarbonyl compounds in Robusta coffee

“…According to previous studies, Robusta showed considerably higher concentrations of pyrazines than Arabica, whereas furans were higher in Arabica [27] . These differences can have a negative effect on the overall coffee flavor, as pyrazines and phenols contribute to its bitter odor [28] . The earthy odor related to pyrazines was stronger in the coffee containing higher levels of Robusta beans in blended coffee [29] .…”