Rennet coagulation of sheep milk processed by ultrafiltration at low concentration factors

► Curd firmness and curd firming rate increase on UF sheep milk concentrates. ► Cheese matrix improvement by UF at low concentration factor. ► Protein concentration leading to earlier curd firmness. The ultrafiltration (UF) of sheep milk is carried out in concentration mode in order to evaluate the variation of the rennet clotting properties of the concentrates as a function of the volumetric concentration factors up to a value of 2.0. The UF unit is equipped with 25.5cm2 of membrane surface area. The cellulose acetate laboratory – made membrane has a molecular weight cut-off of 7000Da. The evolution pattern of the rennet clotting properties of the skimmed sheep milk feed and UF retentates was assessed by the Optigraph. A significant increase on curd firmness and rate of curd firming was detected with the increase of the protein concentration, while RCT show a tendency to increase with milk protein content. The variation of curd firmness and rate of curd firming with the protein concentration was linear and correlations were established.