STRESS RELAXATION CHARACTERISTICS OF CHEDDAR CHEESE

Abstract

Stress relaxation experiments were conducted by heating a cheese sample (22 mm diameter and 17.5 mm height) at 40, 50 and 60°C in an aluminum cup whose inner diameter and depth were 22 mm and 17.5 mm, respectively. A plunger of 18 mm diameter, which was attached to an Instron type machine, was allowed to compress the cheese instantaneously to 10% deformation. The relaxation of stress was recorded as a function of time. Cheddar cheeses with four different fat content (15.3, 22.8, 37.3 and 45.6% fat dry matter – FDM) and two different moisture content (58.1 and 62.4% moisture in non fat portion – MNFP) at 2, 4, 12 and 24 weeks were used in this study. Generalized Maxwell and empirical Peleg models were used to characterize the stress relaxation behavior of melted cheese. The effect of fat content, moisture content, and age of cheese on stress relaxation behavior was studied. Peleg model well described the stress relaxation behavior of melted cheese (cheeses above 50°C) and eight element Maxwell model predicted better than three element Maxwell and six element Maxwell models. The stress relaxation experiment differentiated the viscoelastic nature of different cheeses due to reduction of fat content, increase in moisture, increase in melting temperature and age of cheese. Stress relaxation test can be used as a tool to systematically study cheese functionality.