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Influence of different amylases on staling of bread and high concentration wheat starch gels. S.
HUG-ITEN, B. Conde-Petit, and F. Escher. Swiss Federal Institute of Technology (ETH), Institute of Food
Science, CH-8092 Zurich, Switzerland.
The influence of three different amylases, a conventional
alpha-amylase, a maltogenic alpha-amylase and a beta-amylase, on the changes in the starch fraction during
staling of bread and of a wheat starch gel model was investigated. Different structural levels were studied in
order to gain a complete picture of the action and the antistaling properties of amylases. Bread was prepared
by a conventional baking procedure. Starch gels were produced by heating a concentrated wheat starch
suspension (40 g/100 g wb) in sealed moulds. Bread and starch gels were characterized by compression
tests, microscopy techniques (light microscopy and confocal laser scanning microscopy), X-ray
measurements and differential scanning calorimetry (DSC). The influence of amylases on bread and starch
gel firmness was found to be different. Recrystallization of starch as measured with DSC and X-ray showed
that retrogradation does not necessarily have to be hindered in order to reduce the firming rate. Microscopy
revealed that retrogradation of starch in bread and starch gels does not only involve changes in the
amylopectin fraction but also of amylose polymers. The observation of antistaling effects of amylases in
starch gels cannot be fully transferred to bread. Based on the integral experimental approach, a model for
bread staling and the role of antistaling amylases on different structural levels of bread is discussed.
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