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
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.