Investigations of the nature and occurrence of starch granule channels and their influence on granular reactions
Abstract
The purpose of these experiments was twofold: (1) to determine if the location of chemical reactions within starch granules can be controlled by altering reaction conditions; and (2) to investigate channels in starch granules and determine the implication of their presence. To address the first objective, a rapid, valid method was needed to locate granular reaction sites. A reflection confocal laser scanning microscopy (R-CLSM) method was developed to locate anionic substituents within granules. The method was applied to two types of derivatizing groups: mono- and distarch phosphate ester groups and the 2-hydroxy-3-sulfonylpropyl ether group, the latter being an anionic analog of the hydroxypropyl group. The method revealed native anionic sites in granules, presumably due to proteins, ionic lipids, and/or phosphate ester groups. To determine the degree to which location of reaction sites is a function of reaction conditions, a constant level of an anionic propylene oxide analog was used and temperature, pH, and swelling inhibiting salt type and concentration was varied during reactions with waxy maize starch granules. Reaction sites were located utilizing the RCLSM method. Results indicated that reaction conditions controlled both uniformity of reaction on a granule basis and molar substitution (MS) levels (in granules reacted with propylene oxide under similar conditions). Channels were discovered for the first time in transitory starch granules of potato, sweet potato, horse chestnut, oak, and hickory leaves. Channels were not observed in storage starch granules in those same plants, except for starch granules from hickory nuts. The fact that channels were observed for transitory granules but not in most storage granules is indicative of the different roles of the two types of granules. Channels were found for the first time in granules of maize and Arabidopsis thaliana leaves. Channels in maize and hl sorghum endosperm starch granules were found to be lined with proteins (including F-actin) and phospholipid. A hypothesis for a biosynthetic role for channels in starch granules is presented.
Degree
Ph.D.
Advisors
BeMiller, Purdue University.
Subject Area
Food science|Agricultural chemicals
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