Abstract
The gelatinization properties of heat-dried and heat-moisture-treated starches were studied by Brabender amylograph and plastograph.1) Amylograms of heat-dried starches could only detect the decrease of viscosity, but plastograms could detect the descent of gelatinization temperature and the decrease of viscosity. When corn starch was dried at 120sC for 20 hours, the whole viscosity curve of plastogram was descended greatly indicating decomposition during heating, and potato starch was more sensitive.2) On plastogram of heat-moisture-treated corn starch, initial gelatinization temperature did not change, but terminal gelatinization temperature rose and peak viscosity decreased. Plastogram of heat-moisture-treated potato starch had a characteristic viscosity curve detecting partial gelatinization and repression for dispersion. Being gelatinized, the temperature where the viscosity began to increase lowered widely, but the longer became the treating time, the higher became the temperature .3) On plastogram, heat-moisture-treated corn starch with 18% moisture did not gelatinized, but potato starch with the same moisture gelatinized during treatment. So, plastogram can detect gelatinized starch more sensitively than X-ray diffractmetry.
