Quantifying adulteration in roast coffee powders by digital image processing

A new method based on digital image processing used to quantify adulteration in roast and ground coffee beans is presented in this study. Pure arabica coffee and mixtures of coffee husks and straw, maize, brown sugar and soybean were produced in our laboratory as investigation materials. Red/Green/Blue (RGB) color composites, magnified twelve times, were generated using a Charge Coupled Device (CCD) camera connected to a stereo microscope and a personal computer with an image processing software package. The percent areas of the contaminants in each image were calculated by the Maximum Likelihood supervised classification technique. Best-fit equations relating weight percentage (g.kg(-1)) and the percent areas were obtained for each coffee contaminant. To test the method, 247 coffee samples of different amounts and types of adulterants were analyzed in the laboratory. ne results showed that the new method developed can analyze precisely and quickly a large number of ground coffee powders.