Effects of sucrose replacement by polydextrose on structure development of cakes.
Full and partial substitution of sucrose with polydextrose, and its effects on
properties of batters and structure development of cakes were studied.
Although substitution levels around 25% did not alter the properties of the
system, higher levels of replacement resulted in significant changes in batter
and cake properties.
The effects of sucrose replacement by polydextrose on starch gelatinization
and egg protein denaturation temperatures were studied by differential
scanning calorimetry in model systems. Experiments showed that
polydextrose raises gelatinization temperature more than sucrose. No
significant difference was found between the two solutes with respect to their
effect on egg protein denaturation.
Dynamic oscillatory experiments showed that the viscoelastic profile of cake
batters is altered when polydextrose is used to replace sucrose. A clear
tendency towards permanent deformation and fluid-like behaviour was
observed with increasing levels of replacement by polydextrose.
Changes in rheological properties of batters with increasing polydextrose
concentration were related to bubble size and distribution of cake batters.
Microscopical techniques were developed to assess the foam characteristics
of batters, before and during heating. Increasing level of replacement
increased the mean size of bubbles and introduced large variation in bubble
size distribution. The lack of uniformity in bubble distribution of polydextrose
batters increased the rate of gas diffusion from the small bubbles to larger
ones. During heating, bubble population of conventional batters expanded
more than that of polydextrose substituted batters.
Changes in bubble expansion rates resulted in cakes of lower volume with
increasing levels of replacement. Assessment of textural properties of cakes
indicated that sucrose replacement at levels around 50% or greater
contributes to weakening the mechanical strength of crumb structure.
Scanning electron microscopy of crumb samples demonstrated changes on
the degree of starch granules swelling, cell wall structure and matrix
development, as a result of sucrose replacement by polydextrose