In this study, a modified colour sorting system was used in the bulgur production line to prevent economical losses in undeveloped and developing countries due to unavailable homogeneous hard wheat i.e. free of foreign and reddish seeds. It is impossible to separate undesired different coloured materials using available wheat pre-cleaning systems. The bulgur production steps were firstly investigated to determine suitable stages for the effective application of the colour sorting system. The modified colour sorting system was applied on the pre-cleaned raw material (wheat), cooked and dried wheat, dehulled-intact-bulgur, milled-unclassified-bulgur and fine bulgur to determine the efficiencies by measuring the colour values, i.e. L, a, b and YI values, and percent purity (% # of acceptable particles/total # of particles) at the sorter inlet-outlet and resort inlet-outlet. It was found that the colour sorting system was not suitable for applying on wheat (raw material), and cooked and dried wheat due to their surface properties and not present dominant colour differences. The L and b values of the dehulled-intact-bulgur and milled-unclassified-butgur increased after the sorting system in contrast to decrease in the a and YI values due to the removing reddish or brown bulgur and foreign materials. Each colour value illustrated that the colour sorting system increased the colour quality of bulgur. The increase in the particle size of bulgur increased the efficiency of the colour sorting system to 99.10%. The protein content of the dehulled-intact-bulgur was increased from 12.55% to 12.69% due to removing undesired materials by the colour sorter and the product quality increased. By using the colour sorting system in the bulgur processing line, bulgur quality, product acceptability and production flexibility can be increased. (c) 2005 Elsevier Ltd. All rights reserved.