Effects of modulated differential scanning calorimetry (MDSC) variables onthermodynamic and kinetic characteristics during gelatinization of waxy rice starch
Vmf. Lai et Cy. Lii, Effects of modulated differential scanning calorimetry (MDSC) variables onthermodynamic and kinetic characteristics during gelatinization of waxy rice starch, CEREAL CHEM, 76(4), 1999, pp. 519-525
The total, reversing, and nonreversing thermal properties during gelatiniza
tion of waxy rice starch (starch-to-water ratio = 1:2, w/w) were examined b
y modulated differential scanning calorimetry (MDSC). The effect of MDSC op
erating variables (i.e., the amplitude and frequency of temperature modulat
ion and the underlying heating rate) on these thermal properties was determ
ined by response surface methodology (RSM) and statistical analysis. The fr
equency of temperature modulation and the underlying heating rate significa
ntly influenced the gelatinization temperatures and enthalpy changes in tot
al and nonreversing endotherms. In addition, the combination of 0.025Hz and
4-8 degrees C/min with a properly low degree of oscillation was suitable f
or characterization of starch gelatinization by MDSC. The enthalpy changes
in the reversing (thermodynamic) endotherms increased, but those in the non
reversing (kinetic) endotherms decreased with increasing periods (i.e., dec
reasing frequencies) and underlying heating rates. However, the total entha
lpy changes were only slightly influenced by the MDSC variables studied. In
addition, the activation energies for the total and nonreversing events we
re 281.8-417.3 and 386.3-739.7 kJ/mol, respectively, depending on the MDSC
conditions. From the compensation relationship between the activation energ
y and frequency factor, we concluded that the total and nonreversing endoth
erms were linked to the same single transition.