A study of the molecular relaxations in solid starch using dielectric spectroscopy

A number of relaxations have been observed via dielectric spectroscopy, and possible molecular origins assigned, in a range of gelatinised and granular solid starches. At low temperatures (in the region of - 120 degrees C) two relaxations occur. The evidence indicated that these were due to small motions of the chain backbone and rotation of methylol groups (with the latter process activated at lower temperatures than the former). Around ambient temperature a relaxation proposed to be the glass transition was observed and, in granular starch only, gelatinisation caused a relaxation around 60-80 degrees C. No major differences were discernible between different starch types. The water content was the most important influence on the position of the relaxations, since water acted as a plasticiser. (C) 1999 Elsevier Science Ltd. All rights reserved.