Kasapis S, Sablani S S, Biliaderis C G
Department of Food Science & Nutrition, College of Agriculture, Sultan Qaboos University, Al-Khod, Oman.
Carbohydr Res. 2000 Oct 20;329(1):179-87. doi: 10.1016/s0008-6215(00)00161-0.
Small deformation oscillatory studies were performed on wheat flour paste with a starch content of 75.4%. Work focused on temperatures above 100 degrees C in an effort to seek molecular understanding of such high-temperature processes as bakery operations which are characterised by evaporation of water. The moisture content of the sample decreased from about 32% at 100 degrees C to 6.5% at 130 degrees C. Viscoelastic spectra produced a sigmoidal profile with a disproportionate viscous element also seen in the glass transition of semiamorphous synthetic polymers and high sugar/polysaccharide mixtures during cooling. It is argued that the loss of water upon heating reduces the available free volume between neighbouring chain segments, thus generating a high-density thermoplastic melt suspending granule fragments. The configurational rearrangements of the disordered chains contribute mainly to an energy-dissipating process, as observed in the vitrification of cooled high-solids systems. The equation of Williams, Landel, and Ferry was modified with a 'moisture term' in order to describe the temperature function of viscoelasticity.
对淀粉含量为75.4%的小麦面粉糊进行了小变形振荡研究。研究重点关注100摄氏度以上的温度，旨在从分子层面理解诸如烘焙操作等高温过程，这些过程的特点是水分蒸发。样品的水分含量从100摄氏度时的约32%降至130摄氏度时的6.5%。粘弹性光谱呈现出S形曲线，在半结晶合成聚合物以及高糖/多糖混合物冷却过程中的玻璃化转变中也观察到了不成比例的粘性元素。据认为，加热过程中水分的流失减少了相邻链段之间的可用自由体积，从而产生了悬浮着颗粒碎片的高密度热塑性熔体。无序链的构型重排主要导致了能量耗散过程，这在冷却的高固含量体系的玻璃化过程中也有体现。威廉姆斯、兰德尔和费里方程通过添加一个“水分项”进行了修正，以描述粘弹性的温度函数。
