Characterisation of the rheological properties of mozzarella cheese : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Chemical and Bioprocess Engineering at Massey University, Manawatu, New Zealand

Abstract

An important usage of Mozzarella cheese is as an ingredient in pizza. For this reason, it is important to understand the functional properties of melting and flow behaviours of mozzarella cheeses. For instance, understanding the influence of temperature and moisture on the rheological properties of mozzarella cheese may help cheese the maker to optimise products. A modified UW Meltmeter and rotational methods were used to characterise the rheological properties of mozzarella cheese. The temperature impact on the rheology was determined by measurement over the temperature range from 30 to 80 °C. To investigate the moisture content effect on the rheological properties, mozzarella cheese was dried over different salt solutions or by desiccation in a fridge prior to rheological measurement. Modifications of the UW Meltmeter improved the sample preparation, temperature control during the testing and data analysis. The viscosity data obtained by the UW Meltmeter followed the Arrhenius law with an activation energy of 30.3±1.2 kJ ∙ mol−1. In the rotational method (the shear rate ramp test), the data of viscosity versus shear rate followed the power law model, and the consistency index was fitted to the Arrhenius law and WLF model. The WLF model had a wider temperature range fit than the Arrhenius law. It was found that the viscosity determined from the UW Meltmeter and rotational rheometer was quite different. They are actually measuring different aspects of flow. In this study, the rotational experiment produced results that were more appropriate to explain flow behaviour in cheese in the conditions experienced in pizza baking. The methods to lower the moisture content of mozzarella cheese led to unexpected results where viscosity was not strongly dependent on moisture content. This may have been due to disruption of the structure of the mozzarella cheese during drying.