Some hard cheeses reveal occasionally a brown coloration to be found in their centre after several months of ripening. This is characterised by undesired texture and aroma. Browning is hence considered as a technological defect. Solutions to this problem are proposed in this work by means of experimental design principles. The work followed four steps: (1) identification of the five most important technological parameters, (2) screening of the influencing factors among the five remaining variables via a two levels fractional factorial design, (3) optimisation of the three factors selected in the second step via a response surfaces optimisation design and (4) validation of the new optimised process. Our research identified three main technological parameters responsible for the brown development: temperature of starter culture, added acidity and rennet concentration. The new process aimed at lowering the levels of these three factors. Cheeses made following this process revealed themselves to be less coloured than control cheeses. Although cheeses still displayed the defect, it has been confirmed, that experimental designs could be applied to solve an industrial scale technological problem. (c) 2004 Elsevier Ltd. All rights reserved.