Effects of Emulsifying Method and Setting on Viscoelasticity of Processed Cheese

Abstract

Processed cheese was made at two different rates of heating (10°C/min, 12.5°C/min). Immediately after emulsifying cheese, the specimens were stored at 5°C and 25°C respectively. During the storage of processed cheese, its viscosity and yield value were measured by means of a cone penetrometer, its instantaneous elasticity and stress relaxation by means of a compression type relaxometer, and the stability of emulsion by the oil-off test.
General the viscosity, elasticity and yield value of processed cheese increase with the lapse of the storage time, and its stability of emulsion becomes slightly lower. In two months, its viscosity increases by about 70 percent at 5°C storage, by about 50 percent at 25°C respectively. As the result of stress relaxation shows, its instantaneous elasticity increases by about 40 percent at 5°C storage, by about 50 percent at 25°C respectively, and the relaxation time obtained from a simple model during the storage showed the minimum after 15 days.
Processed cheese made at a lower rate of heating posseses higher viscosity, elasticity and yield value than that processed at higher rate of heating. And also processed cheese made of younger ripened cheese is harder than that made of older kind.
It is considered that the increase of viscoelasticity is due to crystallization of fat in an early stage of storage and to the formation of complete network structure of casein in a later stage.