Degree Type

Dissertation

Date of Award

1993

Degree Name

Doctor of Philosophy

Department

Food Science and Human Nutrition

First Advisor

Jay-lin Jane

Abstract

Granular cold-water-soluble (GCWS) starches were prepared by alcoholic-alkaline treatments. The method was carried out by treating starches with mixtures of ethanol and alkali, primarily NaOH solution (3M), to swell starch granules. The treated starches were then neutralized with HCl (3M, in 100% alcohol), washed with aqueous alcohol solution, and dried in an oven at 80°C for 3 h. The method was effective to wide varieties of starches, including high amylose starches, normal starches, and waxy starches. The efficacy of the method depended mainly on concentrations of NaOH and ethanol, and reaction temperature. Different reaction conditions gave products different properties;Light microscopy revealed that the GCWS starches retained intact but indented granules. The GCWS starch granules showed no Maltese cross when examined by a microscope under polarized light. The x-ray diffraction patterns of the GCWS starches were V types except the GCWS waxy maize starch, which was amorphous. The GCWS starches showed fully swollen granules when dispersed in cold water and exhibited about 70% to 90% of cold-water solubility. Most of the GCWS starch pastes displayed higher viscosity and better freeze-thaw stability than their native counterparts;Controlled release of atrazine encapsulated in GCWS starch matrices was found effective. The study showed that atrazine was physically embedded in starch matrices. Use of GCWS Hylon VII starch as an encapsulated material showed the best encapsulation efficiency. The release rate of atrazine in aqueous ethanol solution (10%, v/v) was affected by the amylose content of the starch, particle sizes, and the temperature. Atrazine encapsulated in high-amylose maize starch matrix displayed a slow release rate. Small particles of encapsulated atrazine product had a fast release rate. In addition, high release temperature tended to increase release rate of encapsulated atrazine. Changes of pH in this study had no significant effect on the release rate of atrazine.

DOI

https://doi.org/10.31274/rtd-180813-12229

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Jen-fang Chen

Language

en

Proquest ID

AAI9413961

File Format

application/pdf

File Size

123 pages

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