The influence of relative humidity and temperature on colour changes in garlic slices has been investigated. The lab colour parameters, lightness, redness and yellowness, were used to determine the colour changes in the environments of isothermal heating at 20, 37 and 50degreesC and relative humidity at 30%, 70% and 90%. The experimental results have shown that temperature and relative humidity greatly affect the redness, yellowness and lightness. A first-order kinetic model is an appropriate representation for describing the changes in the experimental values of the lightness and redness. In contrast to the redness and lightness, the yellowness is described by a first-order kinetics in series, characterised the rise in the yellowness to a maximum value followed by a decrease. According to the experimental results indicated by total colour difference, the maximum browning rate occurs at 70% relative humidity. (C) 2003 Elsevier Ltd. All rights reserved.