Sensory Evaluation Of Coffee In Different Roasting Degrees And Analysis Of The Main Effecting Chemicals

Coffee is one of the most popular drinking around the world. Among the numeriouskinds of coffee species, Arabica and Robust are the most valuable varieties. In this paper,Yunan Arabica coffee and Indian Robust coffee are choosen as the representatives of the twospecies. Both sensory descriptive evaluation and comprehensive chemical analysis wereconducted in the two species of different roasting degrees. Multivariate statistical analysiswere applied to study the influence of roasting degrees on sensory profiles and chemicalcompositions, and to investigate the relationship between sensory attributes and chemicalcomponents. Main results are as following:Sensroy evaluation of coffee roasted in different degrees was studied in this paper. In theaspects of sensory attributes, sensory profiles, sample clusters, spider plots, we havecompared the Spectrum and FP methods. Applying the Spectrum method, the panelistsscreened15coffee descriptors which could be easily understood in the Chinese culture, andabtained the sensory map of the samples. Most of the sensory attributes are less stronger inRobust than in Yunnan coffee. Robust coffee features a typical barley tea aroma. Raw coffeebeans feature an outstanding green note and beany note. With the increase of roasting degree,the nutty, roasted, rubbery and burnt aroma will all increase. Applying the FP method, thepanelists generated46attributes. But FP can only be used to classifiy the samples, failing togive further descriptive information of each samples. In this study, the Rv coinfidencebetween FP and Spectrm was0.353, showing little corration between the two methods. So weused the Spectrum data in further analysis.Chemical analysis of coffee roasted in different dgrees was also conducted. In lightroating degree, quininic acid and malic acid greatly increased by more than200%, whichcaused the decrease of pH to the lowest point. Then, in dark roasting degree, chlorogenic acidand citric acid decreased, causing the slow increase of pH. The optimized extrcation conditionof HS-SPME GC-MS is appling CVB/CAR/PDMS30-50μm fiber to extrcate the violates for30min at60°C.126kinds of violates have been detected, and the most of them are furan andpryzine components, accounting for approximately40%and10%represently in dark roastingdegree coffee. The total peak area of Yunnan coffee was10%greater than that of Robustcoffee. With the increase of roasting degree, the total peak area greatly increased over300%.Large amounts of violates appear during the roasting period.Multivariate statistics were applied to correlate with cheimals and sensory attributes andto study the main effecting chemicals of each sensory attributes. To distinguish the two coffeevarieties, the most discriminative sensory attributes are baley aroma and bitterness,meanwhile, the most discriminative chemicals are2-methylbutyraldehyde, acetic acid, caffine.To distinguish the roasted beans from raw bean, the most discriminative attributes are grassy,beany, sour aroma, roasted and nutty, meanwhile, the most discriminative chemicals arehexaldehyde, malic acid, trimethyl-pyrazine and2-acetylfuran. To distinguish the coffeeroasted in different degrees, the most discriminative attributes are sour, burnt and spicy,meanwhile, the most important chemicals are citric acid, chlorogenic acid, furfuralcohol, sulfocompound,2,3-Pentanedione and acetaldehyde.