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. 2019 Jan 30:272:251-257.
doi: 10.1016/j.foodchem.2018.07.226. Epub 2018 Aug 3.

Modifying Robusta coffee aroma by green bean chemical pre-treatment

Chujiao Liu  1 , Qian Yang  1 , Robert Linforth  1 , Ian D Fisk  2 , Ni Yang  3
Affiliations

Modifying Robusta coffee aroma by green bean chemical pre-treatment

Chujiao Liu et al. Food Chem. .

Abstract

Green Robusta beans were subjected to pre-treatment with the aim of reducing the perceived aroma difference between Arabica and Robusta coffee. Treatment was a short soaking procedure with varying concentrations of acetic acid (up to 5%). Samples were subjected to thermal treatment (roasted) and ground to a standardised particle size distribution. Aroma compounds were evaluated by headspace analysis using solid-phase microextraction and gas chromatography-mass spectrometry. Pre-treatment significantly affected aroma formation during roasting and resulted in a modified level of pyrazines, furanic compounds and sulfur-containing compounds (p < 0.05). Principal component analysis illustrated that the aroma profile of the pre-treated Robusta coffee was closer to the target Arabica coffee after roasting. Sensory results confirmed that the aroma of the 2% acetic acid pre-treated Robusta brew was similar to Arabica; the maximum inclusion level of Robusta coffee in a blend could be increased from 20% to 80%.

Keywords: Acetic acid; Aroma chemistry; Coffee; GC-MS; Pre-treatment; Sensory analysis.

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Figures

Fig. 1
Fig. 1
Principle component analysis (Bi-plot) of the aroma of Arabica, Robusta and acetic acid treated Robusta coffee (0, 1, 2, 3, 4, and 5% acetic acid).
Fig. 2
Fig. 2
(a) Relative abundance of pyrazines (relative to Arabica) for acetic acid treated Robusta (non-treated Robusta was 193.2 ± 1.8 (mean ± standard deviation)); (b) Relative abundance of furanic compounds (relative to Arabica) for acetic acid treated Robusta (non-treated Robusta was 53.2 ± 5.2); (c) Relative abundance of sulphur-containing compounds (relative to Arabica) for acetic acid treated Robusta (non-treated Robusta sample was 142.9 ± 6.2). Error bars represent for standard deviation.
Fig. 3
Fig. 3
Sensory testing to identify similarity of 20%, 40%, 60% and 80% Robusta blends with the Arabica control (a) non-treated Robusta (b) 2% acetic acid treated Robusta (c) 4% acetic acid treated Robusta. Proportion of discrimination = 30%, β = 0.05; blended samples are similar to Arabica if the number of correct response is less than 36 out of 84 responses, * indicates a significant difference compare with the Arabica control.
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