Analytical method to detect adulteration of ground roasted coffee

In this work, an HPLC-based detection method for identification of coffee powder adulterated with roasted barley, wheat and rice powders was developed by using various chemical indices such as monosaccharides (mannose, rhamnose, glucose, galactose, xylose and arabinose), trigonelline and nicotinic acid. As a quality assurance, the recovery efficiencies were 84.1%-90.2% for the monosaccharides, 113.6% for trigonelline and 114.9% for nicotinic acid. The limits of detection were 0.047-0.070 mmol kg(-1) for the monosaccharides, 0.209 mg kg(-1) for trigonelline and 0.117 mg kg(-1) for nicotinic acid. The glucose concentration in coffee samples adulterated with roasted barley, wheat and rice at 99:1 (w/w) mixing ratio was significantly different from the control coffee sample. The limit of discrimination from adulterated coffee samples was 1% (w/w) when glucose was used as a chemical index (P < 0.05).