Preparation of granular cold-water-swelling corn starches by acetic acid-microwave treatment.
Date Issued
2011
Date
2011
Author(s)
Zheng, Ya-Fang
Abstract
Pre-gelatinized or granular cold-water swelling starch (GCWSS) is widely applied in instant food products. The goal of this thesis was to establish a process to prepare cold-water swelling starch from damped native starch granules by microwave heating. Three corn starches with different amylose contents (waxy, normal and Hylon V) were impregnated with different concentration of acetic acid solution (AcOH) and heated in a domestic microwave oven. As the results showed, the damped starches were rapidly gelatinized by microwave heating. The susceptibility of starches to microwave heating was in the order of waxy > normal > Hylon V. The concentration of AcOH had a significant effect on the gelatinization. In order to obtain the optimal granular integrity and degree of swollen, the response surface methodology was designed to study the influences of the AcOH concentration and microwave time. The waxy corn starch impregnated with 5.9 M AcOH and heated for 22 seconds had the highest swelling power value (at 35°C ) of 4.95 ± 0.38 g/g (predicted from RSM was 3.83 ). The normal corn starch had a maximum swelling power value (at 35°C ) of 6.19 ± 0.2 g/g (predicted from RSM was 5.93 ) by treated 4.9 M AcOH and heated for 37 seconds. A maximum swelling power value (at 35°C ) of Hylon V corn starch was 4.66 ± 0.08 g/g (predicted from RSM was 4.65 ) by treated 4.7 M AcOH and heated for 37 seconds. The birefringence almost disappeared in GCWSS prepared from the normal corn starch shown by microscopic observations and the loss ratio of polarized light reached 92%. Crystalline index of GCWSS prepared from normal corn starch was reduced by 72% than the native starch in the results of X-ray diffraction pattern. The starch pasting profile showed a significant decrease of peak viscosity after treated by AcOH and microwave heating. The molecular weight distribution of starch molecules were not dramatically altered indicated that this acetic acid-microwave treatment is a physical modification.
Subjects
corn starch
microwave heating
acetic acid
cold- water- swelling starch
Type
thesis
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