Final structure, stability and sensory properties of chocolate, that we sense during
chocolate bar consumption, depend on the ingredients and their quantity; moreover these
properties also change during chocolate manufacture. During the production the
chocolate is in its liquid form, therefore the knowing of its rheological properties is
necessary to develop an optimal manufacture process and also for quality control of
intermediate and final products. Viscosity is one of the most important rheological
properties of chocolate also for the consumer, because it determines the perceived taste
in the mouth.
Rheological properties of chocolate are measured with rotational viscometers and
rheometers. Liquid chocolate is a non-newtonian fluid with shear thinning flow
behaviour. Viscosity and yield stress are determined from flow curves, obtained by
rheological measurements, with the use of mathematical models; usually with Casson
model. There are several factors that influence rheological properties of chocolate; these
are shape, size and distribution of solid particles, presence of moisture, content of fats,
content of surface acting agents and the process of conching.
With the help of technical literature I have studied the manufacture and composition of
chocolate, what affects the flow of liquid chocolate and how are the rheological
measurements carried out and the results analyzed. With the help of measurements, taken
from a published research, I have studied the influence of the composition and structure
of three main types of chocolate (white, milk and dark) on their rheological properties.
|
