Shear work induced changes in the viscoelastic properties of model Mozzarella cheese

Three model Mozzarella type cheeses (full-fat, non-fat and full-fat with added tri-sodium citrate) were prepared by working cheese components together at 70 °C in a twin screw Blentech cooker. G′ at 70 °C increased with shear work input suggesting work thickening. At lower shear work inputs (<30 kJ kg−1), cheese behaved like a viscoelastic liquid exhibiting typical entangled polymer melt behaviour with moderate frequency dependence. A definite critical point for structural and viscoelastic transition was identified at higher shear work levels (∼58 kJ kg−1 at 150 rpm). Excessive shear work levels (>70 kJ kg−1) resulted in a viscoelastic solid material exhibiting low frequency dependence. Similar viscoelastic property changes occurred in non-fat cheese suggesting that major changes were taking place in the protein matrix during working. Good correlation was found between oscillatory rheological properties such as G′ and LTmax and the melting properties of test cheeses.