|Institution:||Swedish University of Agricultural Sciences|
|Keywords:||gluten; wheats; proteins; gliadin; glutenins; morphology; polymerization; polymers; chemicophysical properties; Gluten; Protein structure; Nano-scale morphology; Polymerization; Mechanical properties; Gliadin|
|Full text PDF:||http://pub.epsilon.slu.se/11836/|
Gluten proteins ranging in size from 30 000 to several million daltons form one of the largest and most complex polymers in nature. The giant molecular nature and intricate network of the over 100 types of proteins in gluten make structural studies rather challenging. This thesis examines the molecular crosslinking and structural properties of variously sourced gluten and its gliadin and glutenin protein fractions, both as unprocessed proteins and in films and foams. Protein modification through chemical additives, separation procedure and genotype (G) and environmental (E) interactions had an impact on protein polymerization, nano-structure morphology, secondary structures and the mechanical properties of films. The extent of denaturation in the starting material for film formation was of relevance for the development of specific nano-scale morphology and improved mechanical properties of films. When molded into films, non-aggregated starting material such as gliadin with additives and mildly separated gluten indicated both hydrogen- and disulfide-bonded protein network, with some non-reducible covalent crosslinks. These films also showed bi-structural morphology at nano scale. The gliadin films revealed hexagonal structures and additional not previously observed structural units. The films from mildly separated gluten also showed hexagonal and lamellar structural morphology. The films from glutenin and industrially sourced gluten proteins showed a high content of non-reducible covalent crosslinks and unorganized morphology at nano scale. The G and E interactions were associated with strong and weak gluten, resulting in films with various structural and mechanical properties. The mechanical properties of films were found to be influenced by protein structure development. Structural attributes such as relatively high number of disulfide crosslinks compared with non-reducible crosslinks, high β-sheet content and specific nano-scale morphology also led to high mechanical performance of films.