Sequential optimisation of yield and sensory quality of semi-hard cheese manufactured from a mixture of ultrafiltered ewes' and cows' milk

A Plackett-Burman (PB) experimental design was applied as a screening method to eight process factors. This method identified starter concentration and curd cutting size as the most significant parameters affecting the manufacture of semi-hard pressed cheese made from blended milk concentrated by ultrafiltration. Both factors, together with the bacterial starter composition, were subsequently evaluated at two levels in a full factorial design (FD). The PB and FD designs were optimised in accordance with yield and sensory quality. A partial least square calibration identified elasticity and internal and external visual evaluations as the main attributes that increased cheese quality. When the final optimised conditions were applied to the manufacturing process, milk diafiltration or pre-acidification and the cutting step were no longer necessary, making continuous cheesemaking process a simpler and more feasible alternative. The yield was 10% higher at the end of the optimisation with no negative effects on the sensory quality.