Roasted Barley Addition to Coffee: Detection of the Adultrant Barley Marker Using Gas Chromatography, Spectroscopy and Trained Panelists
No Thumbnail Available
Date
2016-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The objectives of this research were to detect the adulterant roasted barley at different
concentrations (5 to 20 % w/w ) in roasted & ground coffee using GC, UV spectroscopy,
Infrared (IR) spectroscopy, trained panelists and also total carbohydrate determination by
difference. The samples used were pure barley, pure coffee, medium & dark roasted coffee and
barley mixtures (50:50%w/w). Compounds identified in GC were 3-Eicosene,(E),2-
Tetradecene,(E)-, 2,4 Di tert butyl phenol and E-15-Heptadecenal based on comparison of
retention times with National Institute of Standards and Technology library. Infrared
spectroscopy qualitative transmission measurement of pure coffee & medium roasted coffee
admixture (5 to 20% w/w barley) showed that the infra red spectra among 5 % to 20 % w/w
barley addition to coffee were not resolved though it was possible to identify the peak regions
useful to discriminate the roasted barley from roasted coffee IR spectra using caffeine molecule,
lipid content and starch presence .The addition of barley,10% to 20% to Harar coffee showed
significant (p<0.05) increase in total carbohydrate content, however the crude ash, crude fat
and crude protein content decreased significantly (p<0.05).The UV spectroscopy analysis
showed that it can discriminate pure coffee from adulterated coffee, 5% to 20% w/w barley
based on UV absorbance measurement. Mean while, trained panelists Quantitative Descriptive
Analysis (QDA) sensory evaluation indicated that, there was no significant (p>0.05) difference
among the adulterated coffee 5% to 20% w/ w barley using pure coffee as a reference with
respect to aroma, acidity, bitterness and body sensory notes. Moreover, pH measurement
revealed no significant (p>0.05) difference between pure Harar coffee and adulterated coffee
brews, 5% to 20 % w/ w barley. In conclusion, coffee adulteration with roasted barley would
have a potential to be detected by gas chromatography analysis and it was observed that
Eicosene,(E)-,2-tetradecene,(E)-,2,4 Di tert butyl phenol and E-15-Heptadecenal were
tentatively identified to be further used for detecting the adulterant barley in roasted and ground
coffee. Infrared spectroscopy couldn’t resolve the addition of 5 % to 20 % w/ w roasted and
ground barley to pure coffee. UV spectroscopy analysis resulted in discriminating pure roasted
and ground Harar coffee from the adulterated coffee as low as 5% w/ w barley addition.
Meanwhile, Sensory evaluation resulted in not discriminating the adulterated coffee samples 5%,
10% and 20% w/ w barley despite pure coffee was presented as a reference. The total
carbohydrate determination by difference could be useful in verifying the adulterant barley in
roasted & ground coffee.
Key words: Adulterant barley; Caffeine; GC; Harar coffee; IR spectroscopy; Panelists; pH; QDA; UV spectroscopy
Description
Keywords
Adulterant barley; Caffeine; GC; Harar coffee; IR spectroscopy; Panelists; pH; QDA; UV spectroscopy