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Starch morphological and molecular structural relations to amylolysis Open Access

Descriptions

Other title
Subject/Keyword
Amylolysis
Cereals
Starch
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Naguleswaran, Sabaratnam
Supervisor and department
Dr. Vasanthan, Thava (Agricultural, Food and Nutritional Science)
Examining committee member and department
Dr. Bressler, David (Agricultural, Food and Nutritional Science)
Dr. Choi, Phillip (Chemical and Material Engineering)
Dr. Eskin, Michael (Human Nutritional Science, University of Manitoba)
Dr. Gaenzle, Michael (Agricultural, Food and Nutritional Science)
Department
Department of Agricultural, Food, and Nutritional Science
Specialization
Food Science and Technology
Date accepted
2013-03-27T15:55:40Z
Graduation date
2013-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
The objective of this research was to investigate the impact of variation in starch morphology and molecular structure among starches isolated from triticale, wheat, corn and barley (normal, waxy, and high-amylose genotypes) on amylolysis. Native starch granules in their unfractionated and fractionated (large and small granules) forms were characterized in terms of their composition, morphology, physicochemical properties and molecular structure [amylopectin (AP) and amylose (AM)]. The degree of hydrolysis (DH) was determined (55oC for 1h and then at 30oC for 72h) using a mixture of α-amylase and glucoamylase. SEM and CLSM studies revealed that surface pores and internal channels were mainly present in large granules of triticale, wheat and corn starches. In corn starches, the surface pores and channels were filled with protein and phospholipids. AM content and crystallinity of starches varied among genotypes, and between large and small granules within a source. Regardless of genotypes, the DH at the initial stage (1h) of hydrolysis of unfractionated triticale was higher than wheat, corn and barley starches. In fractionated starches, small granules were hydrolyzed (at 1h) to a greater extent than large granules due to their larger surface area per unit mass. The data on AP molecular characteristics showed that the average chain length (average-CL) was negatively correlated to weight-average molecular weight (Mw), molecular-size or radius of gyration (Rz), molecular density (ρ) and degree of branching (DB). The enzyme hydrolysis data indicated that, at all stages of hydrolysis, AP was hydrolyzed to a greater extent than AM. Whereas, variation in DH among isolated AP or isolated AM from different starch sources was generally insignificant at all stages of hydrolysis. Furthermore, it was observed that the DH (at 1h) of native unfractionated starches was negatively correlated to average-CL, but positively correlated to Mw, Rz, ρ and DB. Overall, this study indicated that starch amylolysis is influenced by the interplay among: 1) composition (AM content), 2) morphological characteristics (granule size, channels/pores, and associated proteins and phospholipids) and 3) difference in granular architecture (resulting from variation in the AP average-CL).
Language
English
DOI
doi:10.7939/R35Q8P
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Naguleswaran et al. (2013). Food Research International, 51:771-782Naguleswaran et al. (2012). Carbohydrate Polymers, 88:864-874.Naguleswaran et al. (2011). Cereal Chemistry, 88(1):87-94.

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