Modulating the structure of plant-based protein dispersions

Ramadhan, Kurnia (2020) Modulating the structure of plant-based protein dispersions. PhD thesis, University of Nottingham.

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Abstract

The aim of the work presented in this thesis is to understand the formation of protein solidified gel network with controlled structures prepared from commercially established plant-based protein materials. Different types of soy protein isolates were characterised at various structural length scale. At molecular scale, results obtained from gel electrophoresis, scanning calorimetry, and infrared spectroscopy showed that variations in polypeptide constituents and protein conformations led to a different protein solubility in water. At mesoscopic length scale, soy protein isolates insoluble fraction was characterised as protein particles with diverse range of shapes and size distributions. At macroscale, viscoelastic behaviour of protein particles with the largest mean diameter size required the lowest isolate concentration due to their high dispersed phase volume.

Heat-induced protein gel was prepared from soy protein isolate with limited solubility. The presence of either calcium chloride or microbial transglutaminase enzyme is required to achieve a solidified structure. The addition of calcium chloride altered protein spatial structure leading to formation of denser gel matrices. In contrast, the presence of microbial transglutaminase enzyme increased the dynamic moduli without losing the water retaining ability of initial spatial structure as favoured by newly formed covalent linkages.

The usability of low purity protein material derived from oat bran was also investigated. Structural properties of oat bran protein-rich material indicated the aggregated protein conformation and the presence of carbohydrate and lipid in complex form. Ball milling treatment not only reduced the particle size of protein material, but also altered the conformation of the chemical constituents. A high solid concentration, i.e. 30%, is required to achieve a stable oat bran protein dispersion. Dynamic moduli of dispersion increased as a result of heat-induced structure formation.

Mechanical properties of protein gels containing mixtures of soy protein isolate and oat bran protein-rich material were evaluated. Gel structure was mainly built from soy protein, whereas oat bran protein was used as filler particles. Increasing filler concentrations to the gel matrix led to a more stiff and brittle protein gel structure. Addition of filler particles at higher concentration to the enzymatically crosslinked gel matrix increased both stiffness and elasticity of the gel structure. The provided insight from this work will be beneficial to the development of plant-based novel protein-rich foods.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Foster, Tim
Keywords: Food protein, Structural properties, Viscoelasticity, Soybean, Oat bran
Subjects: T Technology > TP Chemical technology > TP 368 Food processing and manufacture
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 59796
Depositing User: Ramadhan, Kurnia
Date Deposited: 15 Jul 2020 04:40
Last Modified: 15 Jul 2020 04:40
URI: http://eprints.nottingham.ac.uk/id/eprint/59796

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