Ph.D. Final Examination Seminar

Ph.D. Final Examination Seminar

Published: November 20, 2013

The doctoral student, Hua Chen, will defense for her Ph.D. on November 25, 2013 (2 p.m.) at the NLSN Food Science Buidling at Purdue University. Chen received an M.S. in Food Science from South China University of Technology (P.R. China) in 2009. She later joined Dr. Yuan Yao' research group to pursue her Ph.D. Her research focused on the structure of carbohydrate based nanoparticles and their functional properties such as digestibility, interfacial absorption, and controlled delivery of lipophilic compounds. She will give a lecture entitled "Structure and functions of highly-branched alpha-D-glucans".

Phytoglycogen (PG) is a highly branched alpha-D-glucan naturally occurring in plants. PG has been identified to bear a structural resemblance to glycogen isolated from animal sources. PG is primarily composed of short B chains attached by additional short B and/or A chains. It is known for its high molecular density with a density increment from the core towards the outer surface of the particulate. So far, the branch structure of PG, such as the organization of neighboring branch points remains largely unexplored.

In this research, beta-amylolysis was used to investigate the branch structure of PG. First, the maltose yield and time course of chain length distribution of PG beta-dextrins during beta-amylolysis were monitored and compared to those of waxy corn starch (WCS). It was found that PG exhibited a resistance to the action of beta-amylase and the beta-amylolysis limit of PG was significantly lower than that of WCS. Second, the chain length profile of beta-dextrins was evaluated using chromatographic method. An analysis of the possible organization of branch points will be presented. This information will provide insight to the branching pattern of PG as compared to WCS. Third, the changes in molecular weight, root mean square radius, and dispersed molecular density were evaluated for PG and WCS beta-dextrins as a function of the degree of beta-amylolysis. In this work, the functions of PG were also explored.