Retrogradation behavior of some wheat starches and relation to staling of bread The retrogradation of amylopectin is the main factor responsible for the staling of bread, e.g.
the increase in firmness during storage of bread. However, studies are appearing where it is
shown that the use of a waxy wheat starch improves the shelf life of bread. The question is
why would a waxy starch reduce staling of bread? As waxy starches contain almost only
amylopectin, and no amylose, it would be expected that these starches should retrograde more
than the normal starch with around 75% amylopectin and 25% amylose.
There might be several explanations for the influence on bread staling. There might be
differences in the water holding capacity between the starches, something that might influence
moisture relations during storage. The retrogradation behavior might also differ between
starches differing in amylopectin content, and such differences could result in a different
development of firmness.
In this project the retrogradation behavior of some different starches will be investigated.
Normal wheat starch, waxy wheat starch, durum wheat starch and waxy durum wheat starch
will be included in the study.
The project will start with a literature study to summarize what is found in literature about
retrogradation and bread staling for waxy starches. Starch retrogradation will be followed
using differential scanning calorimetry (DSC), and retrogradation will be studied as a function
of, for example, time, water content, and temperature. DSC can also be used to study the
amount of unfreezeable water during storage. Texture analyzer will be used to follow the
development of firmness during storage. Baking experiments might also be performed.
The project is performed in collaboration with Colin Jenner, School of Agriculture and Wine,
Adelaide University, South Australia
Supervisors: Ann-Charlotte Eliasson, ann-charlotte.eliasson@food.lth.se and
Jeanette Purhagen, jeanette.purhagen@food.lth.se
Division of Food Technology, Lund University
2008-02-13