Comparison of model Mozzarella cheese made from extract of tamarillo fruit (Cyphomandra betacea (Cav.)) and calf rennet

Abstract

In this thesis, model Mozzarella cheeses were made from a protease (tamarillin) extracted from tamarillo (Cyphomandra betacea (Cav.)) fruit and commercial natural calf rennet. Mozzarella is one of the most consumed cheeses in the international market, mainly used in pizza topping. The protease purified from the red Laird’s Large cultivar exhibited its highest proteolytic activity towards all three kinds of major protein caseins: α-, β-and k-casein. While rennet displayed preferable hydrolysis to k-casein. Mozzarella samples were prepared with two concentrations of tamarillo enzyme extract, 0.75g per litre milk,0.5g per litre milk and 0.077ml of 280 IMCU rennet per litre milk. Significant higher moisture content was found in low concentration tamarillo extract coagulated cheeses than rennet coagulated cheeses. Significant higher protein content was found in rennet coagulated cheeses than both concentration tamarillo extract coagulated cheeses. No significant difference in the lipid content was found between cheeses made with rennet and tamarillo extract. Significant higher ash content was found in rennet coagulated cheeses than both concentration tamarillo extract coagulated cheeses. Mozzarella coagulated with tamarillo extract exhibited a darker and browner colour, compared with rennet coagulated cheeses. These might be caused by the colour pigment left in the tamarillin extract. The tamarillo enzyme exhibited rennet-like milk-coagulation properties and significant higher yield of cheese. The results of confocal laser scanning microscope (CLSM) revealed a clearer anisotropic heterogeneous structure of Mozzarella made with rennet when heated to the melting temperature 75°C. After heating, the elongated lipid columns interspersed between proteins coalesced to form large spherical lipid droplets in Mozzarella cheeses made with rennet and tamarillo protease. Looser protein network and larger voids were observed in the mozzarella cheeses coagulated with tamarillo protease, which might be resulted by its extensive hydrolysis of all major caseins. Mozzarella cheeses made with rennet and tamarillin exhibited similar melting qualities. The tamarillo protease showed faster milk gelation kineticsin the beginning of coagulation, compared with rennet. The milk-clotting activity of tamarillo protease increased with the increasing concentration. All cheese samples exhibited larger elastic behaviour and viscos behaviour with increasing temperature. While a weaker elasticity and viscosity was found in cheeses obtained from high concentration tamarillo protease.