Effect of storage temperature on the ageing of concentrated wheat starch gels

Flour Milling and Baking Research Association, Chorleywood, Rickmansworth, Herts. Using differential thermal analysis (d.t.a.) the progress of ageing of concentrated wheat starch gels stored at temperatures from−1° to 43° has been investigated. A very close relationship has been found between the ageing of starch gels as measured by d.t.a. and the staling of bread as measured by crumb firmness at storage temperatures of−1°, 10° and 21° but some differences have been found at 32° and 43°. The results at −1°, 10° and 21 ° provide very strong confirmatory evidence that starch crystallisation is the chief factor in the firming of bread. At elevated storage temperatures (32° and 43°) the róle of starch crystallisation in the firming of bread apparently gradually diminishes. Analysis of the results indicates that the mechanism of crystallisation of the starch, instantaneous nucleation followed by rod‐like growth of crystals, is the same over the whole range of storage temperatures −1° to 43°. Evidence is also presented to show that there is a possibility that at higher storage temperatures a more symmetrically perfect crystal structure is being formed.