Stress relaxation/creep compliance behaviour of kashar cheese: Scanning electron microscopy observations

Abstract

In this study, uniaxial and creep analyses were used to characterise stress relaxation and creep compliance behaviour of kashar cheese as a function of different compression (1.5, 3.0, 4.5, 6.0 and 7.5 mm) and stress (12.25, 24.50, 36.75, 49.00 and 61.25 kPa) levels. For this purpose, mechanical simulation models, namely generalised Maxwell, Nussinovitch, Peleg and Burger models were used to simulate the viscoelastic behaviour of kashar cheese as a function of different compression and stress levels. The results revealed that the compression levels could remarkably change internal structure and deformation properties of kashar cheese. Stress relaxation test demonstrated that kashar cheese showed more elastic behaviour, namely higher resistance to deformation at higher compression levels. Creep tests showed that rigidity of kashar cheese decreased as the stress level applied increased. Scanning electron microscopy (SEM) images showed that compression resulted in a less homogeneous protein matrix, an interrupted casein/fat network, and destroyed fat globules by forcing them to exude from the cheese surface. These results should be useful for dairy industry.