The software transposes the images to the HSI colour space and then calculates the hue value for each pixel in the pictures of the semi-automatically segmented gum wafers. If the colours are not mixed, two well-separated peaks on the hue axis are present which will gradually converge with increasing colour mixture. "Hue" is an angle in the HSI colour space, thus the circular variance of hue is defined as 1 minus the length of the average vector. ViewGum© displays the standard deviation between those colour peaks by taking the square root: SD = sqrt (Variance of Hue) 20. For consistency, the term Variance of Hue (VOH) will be used 18; it is considered as the measure of chewing performance in the context of this test - with a lower VOH indicating a higher the colour mixture and therefore a better chewing efficiency.