Colour of hard cheese

During ripening, body colour of Emmental cheeses was evaluated by tristimulus reflectance measurements. Tristimulus primaries were transformed to the Helmholtz system and into CIELAB-coordinates in order to obtain interpretable results. Apart from lightness decreasing with increasing maturation time, it was found by using both systems that, (1) colourfulness increased continuously up to a cheese age of approximately 10 weeks and then remained constant, and (2) the hue of the cheese body shifted towards a slightly more orange colour in the last stage of ripening. The yellowness index, which represents a one-dimensional measure calculated from tristimulus primaries, is proposed as a simple and adequate measure of cheese body colour, and interrelations with CIELAB-values commonly used in food science are outlined.