Investigate continuous cheesemaking.

European scientists are developing a continuous cheesemaking process that will deliver a product with the quality found in cheese made from batch processes. A continuous process would have both technological advantages and economic benefits as well.

Up to now, two approaches to continuous cheesemaking have been pursued by the dairy industry. In one of these processes, coagulation occurs within coagulators and separators. Here, the input is destabilized milk and the output is drained curd. The other process involves the membrane-mediated concentration of milk to the dry matter content of cheese, which avoids drainage. But both techniques give a much lower cheese quality than conventional methods.

The current project entails combining both of these processes. Researchers are constructing a pilot plant for the continuous production of cheese in which the enzymatically destabilized milk is separated from the clotting phase, and the curd is concentrated to its final dry matter content by a membrane.

Investigators based their choice of the membrane for the bioreactor on minimum enzyme release. Membranes made from different materials and with different geometries were tested. Their performance varied considerably. Membrane hydrophobicity was positively correlated with the amount of immobilized chymosin. But a high hydrophobicity induced the formation of a milk protein layer on the membrane. This resulted in a rapid inactivation of the immobilized enzyme.

The best membrane was then used to create a membrane bioreactor with a spiral configuration. A tubular heat exchanger was constructed in which coagulation occurred without excessive breakdown of the gel structure. The residence time within the heat exchanger could also be varied to give the desired consistency. A high flow rate in the bioreactor promotes shear phenomena that remove the enzyme from the surface of the membrane. In the heat exchanger, excessively high flow rates can desegregate the casein network prematurely. This has implications for designing pumps to prevent high losses of protein. Researchers have begun to study milk coagulation and curd concentration. Preliminary pilot scale results suggest a positive outcome.

Further information. Dr. Ir. F. Cuperus, ATO-DLO, PO Box 17, NL-6700AA, Wageningen, The Netherlands; phone: [phone]; fax: [phone]; email: [e-mail].