E. Vesterinen et al., Effects of preparation temperature on gelation properties and molecular structure of high-amylose maize starch, CEREAL CHEM, 78(4), 2001, pp. 442-446
In this study, 3% aqueous high-amylose maize starch (Hylon VII) dispersions
were heated to temperatures of 140-165 degreesC. The onset and rate of gel
formation was observed using a small-strain oscillation rheometer as a fun
ction of temperature from 90 to 25 degreesC. The gel formation clearly bega
n earlier in high-amylose starch paste preheated at lower temperatures, but
the rate of gelation was slower and the resulting gel was weaker in compar
ison with starch pastes preheated at higher temperatures. In addition, the
structure of the final gels was studied using large deformation compression
measurements. The most rigid gel structure on the basis of small and large
deformation tests was obtained for high-amylose starch gel preheated to 15
0-152 degreesC, depending on the type of measurement. The rate of gelation
was also fastest in that temperature range. High-amylose gels heated to hig
her temperatures lost their rigidity. The molecular weight distribution of
starch molecules was measured by size-exclusion chromatography. Heating cau
sed extensive degradation of amylopectin, which had a great effect on amylo
se gel formation and the final gel properties of high-amylose maize starch.
Micrographs of Hylon VII gels showed that phase separation of starch compo
nents visible in light microscopy occurred on heating to higher temperature
s.