Rheological Properties of Mozzarella Cheese Curds

Abstract

The fibrous-structured cheese, called "string cheese", is made from Mozzarella cheese curds by kneading and stretching it. At first, the stretching process was performed by each cheesemaker's individual skill. To mechanize this stretching and hardening process, the rheological properties of the curds such as Young's modulus, viscosity and relaxation time were determined in relation to the process. The results obtained were as follows. Since both Young's modulus (Fig.4) and viscosity (Fig.12) of the curds varied markedly with temperature, we assumed that temperature control is a very important factor in string cheese production. From the apparent viscosity and relaxation time, which were calculated from a rheological model consisting of only one Maxwell model (Figs.8, 9), it was suggested that the curds lost their fluidity and hardened at temperatures below 35°C. Consequently, the molding process of the curds should be finished above that temperature. Yield value of the curds was not observed at temperatures above 50°C and flow behavior was similar to Newtonian in the temperature range of 50 to 60°C (Fig.11). Poisson's ratio ( σ) of the curds was about 0.5, and shear modulus (G) and normal viscosity (λ) were calculated by using the following equations. G=E/2(1+σ), λ=(1+σ)Mechanization of Fibrous-Structured Cheese Production Process. I.