Biological Systems Engineering


Date of this Version

Summer 7-28-2011


A Thesis Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agricultural and Biological Systems Engineering, Under the Supervision of Professor Yiqi Yang. Lincoln, Nebraska: July, 2011

Copyright 2011 Wei Li


Gliadin was reacted with citric acid under weak acidic and weak alkaline conditions in both wet and dry states and the reaction mechanism was studied. The low morphological stability in an aqueous environment and inferior mechanical properties have restricted the applications of plant proteins, although these materials possess a unique structure, biocompatibility and biodegradability. Carboxylic acids such as citric acid are inexpensive and nontoxic chemicals and are preferred for crosslinking proteins and cellulose to improve the desired properties of the materials.

In this study, gliadin was chosen as a model of plant proteins to react with citric acid. However, previous research only provided limited evidences to support the presence of the acylation reaction, such as improvement in mechanical properties. To explore the reaction mechanism, titration method was used to investigate the influences of pH, citric acid concentration and reaction temperature on both carboxyl and amine group changes during the reaction. The kinetic parameters of both reaction states have been obtained at different temperatures. Additionally, to further improve the crosslinking degree, a dry state crosslinking of gliadin films with citric acid was also studied. A relationship between the mechanical properties and the crosslinking degree has also been developed.

Advisor: Yiqi Yang