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

Coffee beans from the same origin were roasted using six time-temperature profiles, in order to identify volatile aroma compounds associated with five common roast coffee defects (light, scorched, dark, baked and underdeveloped). Thirty-seven volatile aroma compounds were selected on the basis that they had previously been identified as potent odorants of coffee and were also identified in all coffee brew preparations; the relative abundance of these aroma compounds was then evaluated using gas chromatography mass spectrometry (GC-MS) with headspace solid phase micro extraction. Some of the 37 key aroma compounds were significantly changed in each coffee roast defect and changes in one marker compound was chosen for each defect type, that is, indole for light defect, 4-ethyl-2-methoxyphenol for scorched defect, phenol for dark defect, maltol for baked defect and 2,5-dimethylfuran for underdeveloped defect. The association of specific changes in aroma profiles for different roast defects has not been shown previously and could be incorporated into screening tools to enable the coffee industry quickly identify if roast defects occur during production.