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%.
Highlights
According to the International Coffee Organization (2018a), global coffee consumption is 148 million cups per year and despite the background of global inflation, continued price fluctuations and restrictions on trade, there is a continued increase in demand for high quality coffee and speciality coffees (Bhumiratana, Adhikari, & Chambers Iv, 2011)
Twenty-four aroma compounds were identified within all the coffee samples (Table 1)
The detailed information for 24 aroma compounds is illustrated in the Supplementary material (CAS number, molecular weight, significant fragments, probability from NIST database, odour threshold and chromatogram obtained by solidphase microextraction (SPME)-Gas chromatography-mass spectrometry (GC-MS) analysis)
Summary
According to the International Coffee Organization (2018a), global coffee consumption is 148 million cups per year and despite the background of global inflation, continued price fluctuations and restrictions on trade, there is a continued increase in demand for high quality coffee and speciality coffees (Bhumiratana, Adhikari, & Chambers Iv, 2011). Robusta coffee is less expensive (International Coffee Organization, 2018b), and is often blended with Arabica coffee beans to reduce cost, enhance crema formation (Folmer, Blank, & Hofmann, 2017) and create specific aroma profiles. It is common that coffee blends contain a mixture of 50/50 Arabica and Robusta (Dias et al, 2018). There is a potential for up-valuing and improving the quality of Robusta coffee beans. This has the explicit goal of reducing the sensory difference, thereby making Robusta coffee flavour more like Arabica, increasing the range of choice for consumer at a lower final product cost
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