Syneresis follows the cutting of milk coagulum into cubes and is promoted by stirring. Important cheese properties such as moisture, mineral and lactose content and texture are affected by rate and extent of syneresis. The objective of this study was to monitor syneresis indices and whey composition over the course of syneresis using colour parameters derived from a fibre-optic sensor, with a view to achieving higher levels of process control and thus improved cheese quality. A full factorial design consisting of three levels of milk fat content, three levels of gel cutting firmness and three replicates was used in this study to give a wide range of syneresis conditions. It was found that the technology can be used to predict curd moisture (R(2) = 0.91, P < 0.001) and fat content of whey (R(2) = 0.89, P < 0.001) during syneresis. The results obtained show that the sensor has potential to monitor syneresis using colour parameters and therefore allow improved control of Curd moisture content before ripening, which would decrease the production of down-graded cheese. (C) 2008 Published by Elsevier Ltd.