Roasted Barley Addition To Coffee Detection Of The Adultrant Barley Marker Using Gas Chromatography Spectroscopy And Trained Panelists

The objectives of this research were to detect the adulterant roasted barley at differentrnconcentrations (5 to 20 % w/w ) in roasted & ground coffee using GC, UV spectroscopy,rnInfrared (IR) spectroscopy, trained panelists and also total carbohydrate determination byrndifference. The samples used were pure barley, pure coffee, medium & dark roasted coffee andrnbarley mixtures (50:50%w/w). Compounds identified in GC were 3-Eicosene,(E),2-rnTetradecene,(E)-, 2,4 Di tert butyl phenol and E-15-Heptadecenal based on comparison ofrnretention times with National Institute of Standards and Technology library. Infraredrnspectroscopy qualitative transmission measurement of pure coffee & medium roasted coffeernadmixture (5 to 20% w/w barley) showed that the infra red spectra among 5 % to 20 % w/wrnbarley addition to coffee were not resolved though it was possible to identify the peak regionsrnuseful to discriminate the roasted barley from roasted coffee IR spectra using caffeine molecule,rnlipid content and starch presence .The addition of barley,10% to 20% to Harar coffee showedrnsignificant (p0.05) difference between pure Harar coffee and adulterated coffeernbrews, 5% to 20 % w/ w barley. In conclusion, coffee adulteration with roasted barley wouldrnhave a potential to be detected by gas chromatography analysis and it was observed thatrnEicosene,(E)-,2-tetradecene,(E)-,2,4 Di tert butyl phenol and E-15-Heptadecenal wererntentatively identified to be further used for detecting the adulterant barley in roasted and groundrncoffee. Infrared spectroscopy couldn’t resolve the addition of 5 % to 20 % w/ w roasted andrnground barley to pure coffee. UV spectroscopy analysis resulted in discriminating pure roastedrnand ground Harar coffee from the adulterated coffee as low as 5% w/ w barley addition.rnMeanwhile, Sensory evaluation resulted in not discriminating the adulterated coffee samples 5%,rn10% and 20% w/ w barley despite pure coffee was presented as a reference. The totalrncarbohydrate determination by difference could be useful in verifying the adulterant barley inrnroasted & ground coffee.rnKey words: Adulterant barley; Caffeine; GC; Harar coffee; IR spectroscopy; Panelists; pH; QDA; UV spectroscopy

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