High shear cooking extrusion to create fibrous mozzarella cheese from renneted and cultured curd

Abstract

To understand shearing on cheese curds during high shear extrusion, the controlable parameters of a twin-screw extruder were related with measured and calculated parameters that characterise the extrusion process effects on product properties. Curd properties were correlated with specific mechanical energy SME (23–390 kJ·kg−1), Texit (22–54 °C) and residence time RT (36–507 s); the wide experimental range studied provided new insights regarding extrusion of cheese curds. Longer and finer fibers were produced at low SME (23–27 kJ·kg−1), high Texit (50–54 °C) and short RT (55–60 s). Whereas extruded curds produced at high SME (166–390 kJ·kg−1), low Texit (22–23 °C) and long RT (371–396 s) tend to form a compact structure with less fiber formation. Temperature in the heating section, Th, and temperature of the cooling die, Tc, were found to determine critical curd phase transitions during extrusion, from viscoelastic solid to viscoelastic liquid and vice versa, that are important for the creation of fibrous cheese curd structures. Tc was the most important factor influencing SME, indicating the considerable contribution of the cooling process in increasing the shear forces. Curd composition and textural properties were significantly influenced by Th and Tc, showing that a higher Th enhances curd elasticity and reduces melt strength while a higher Tc induces lower water content and increases melt strength. We concluded that a variety of structured mozzarella products with customized properties can be produced by controlling the extrusion parameters.