Starch gelatinization in ohmic heating
1997
Wang, W.C. | Sastry, S.K.
The effect of starch gelatinization on electrical conductivity (sigma) was investigated in this study. Suspensions of corn and potato starch were prepared with a starch:water ratio of 1:5 (w/w) by mixing with the appropriate amount of water. Suspensions were ohmically heated with agitation to 90 degrees C by AC at 60 Hz, and a voltage gradient of 20 V/cm. Partially gelatinized and fully gelatinized samples, prepared by preheating suspensions to or beyond the gelatinization ranges, were also tested. Gelatinization energy (delta H(G)) and degree of gelatinization (%SG) of each sample were determined by differential scanning calorimetry (DSC) at a scanning rate of 10 degrees C/min. The results showed that endothermic gelatinization peaks were found on both DSC thermograms and electrical conductivity curves, with similar shapes and temperature ranges. Data of %SG obtained from conductivity curves and DSC thermograms were in agreement in low and mid-gelatinization ranges but were different when %SG was high, due to high ohmic heating rate. Electrical conductivity increased with temperature, but decreased with degree of gelatinization, apparently caused by structural changes and an increase in bound water.
اظهر المزيد [+] اقل [-]الكلمات المفتاحية الخاصة بالمكنز الزراعي (أجروفوك)
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