HighlightsCoffee was roasted and five typical roasted defects were replicated.Light roast defect had increased indole.Scorched roast defect had increased 4-ethyl-2-methoxyphenol.Dark and baked roast defect had increased phenol and maltol respectively.Underdeveloped roast defect had increased 2,5-dimethylfuran.

The demand for high quality and specialty coffee is increasing worldwide. In order to meet these demands, a more uniform and standardized quality assessment of coffee is essential. The aim of this study was to make a sensory scientific and chemical characterization of common roasting defects in coffee, and to investigate their potential relevance for consumers' acceptance of coffee. To this end, six time-temperature roasting profiles based on a single origin Arabica bean were developed: one 'normal', representing a reference coffee free of defects, and five common roast defects ('dark', 'light', 'scorched', 'baked' and 'underdeveloped'. The coffee samples obtained from these beans were evaluated by means of 1) aroma analysis by Gas Chromatography-Mass Spectrometry (GC-MS), 2) sensory descriptive analysis (DA) by trained assessors, and 3) hedonic and sensory evaluation by consumers using a Check-All-That-Apply (CATA) questionnaire. Multivariate analyses of aroma, DA, and CATA data produced similar sample spaces, showing a clear opposition of the light roast to the dark and scorched roasts), with the normal roast having average values of key aroma compounds. The DA data confirmed this indications and showed the normal roast to have a balanced sensory profile compared to the other defects. Importantly, the normal roast was also significantly preferred in the consumer

Highlights:1. Varying levels of sugars were used to pre-treat Robusta green beans.2. Treatment increased the similarity of Robusta to Arabica.3. The optimum level of sugar treatment was Robusta soaked in 15F solution.4. For coffee aroma the blending ratio can be increased from 20% to 80% Robusta.5. The aroma of treated Robusta coffee was more stable than Arabica.

HighlightsDifferent levels of acetic acid were used to pre-treat Robusta green coffee beans.Acetic acid pre-treated Robusta had a more similar aroma profile to Arabica.The optimum level of acetic acid treatment was 2%.The maximum level of Robusta coffee added in a blend increased from 20% to 80%.

which is critical for its eating quality and understanding the biochemistry and genetics of aroma is important for molecular breeding of millets rich in aroma. In this study, the volatile aroma compounds of the elite millet variety Jingu 21 were investigated at different cooking times, pH, processing methods, and compared with 3 other varieties. An in-vial cooking method was developed which combined solid phase micro-extraction and gas chromatography-mass spectrometry for the detection and identification of volatile compounds. The main findings were: a) Twelve aroma compounds were identified during cooking, which were hexanal, heptanal, octanal, (E)-2-heptenal, nonanal, trans-2-octenal, trans-2-nonenal, 2,4-nonadienal, (E,E)-2,4-decadienal, 1-octen-3-ol, 2-pentylfuran and 6-methyl-5hepten-2-one. b) Longer cooking times produced higher concentrations of aroma compounds. c) Variations in cooking pH (from 6 to 8) had no obvious impact on the aroma of the millet porridge. d) More volatile compounds were released from millet flour compared to millet grain. e) There were significant differences among varieties and Jingu 21 millet showed the highest abundance of most aroma compounds, explaining partly why it is strongly favored by consumers for decades.