12:30 pm - 1:30 pm
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Hongmin Dong. This seminar is open to the general public to attend.
Meeting ID: 932 5083 6087 Passcode: 235315
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Thesis Topic: Modification of pulse starch properties by nanoparticulation and phosphorylation techniques
PhD with Dr. Thava Vasanthan
The global demand for plant-based protein is fast growing. This has resulted in significant expansion of pulse grain fractionation and value-added processing operations that primarily focus on protein refining. Pulse starches, as the major by-product of those operations, remain underutilized due to shortcomings in their functionalities, especially high retrogradation capacity after aqueous gelatinization. Therefore, modification of pulse starch to improve their properties is important for their wider use in food and industrial applications. This research mainly focused on improving the functionality of pulse starches by the application of nanotechnology and phosphorylation techniques. The objectives were: a) to define a sustainable and cost-efficient protocol for pulse starch nanoparticles (SNPs) preparation, b) to study physicochemical and rheological properties of SNPs produced from pulse starches in comparison to cereal starches, c) to investigate continuous approaches for the production of SNPs and their use in Pickering emulsions, and d) to investigate how phosphorylation, a popular chemical modification technique for starches, would influence the physicochemical and functional properties of pulse starches. The SNPs were prepared for the first time via a combination of ultrasonic-assisted dissolution of starch and subsequent rapid nanoprecipitation by using ethanol as an antisolvent. Different processing parameters were investigated, and an optimum protocol that is suitable to generate the smallest nanoparticles with the least amount of ethanol was identified. The results showed that SNPs from all starches were spherical in shape, where pulse SNPs had smaller and more uniform size than cereal SNPs. Pulse SNPs with higher amylose content showed greater relative crystallinity, enhanced short-range molecular order, and better thermal stability. Rheological studies confirmed that variations in the starch source as well as SNP morphology and thermal stability influence the viscoelastic properties of SNPs as a function of shear rate, frequency and temperature. Finally, continuous nanoprecipitation techniques such as flash nanoprecipitation (FNP) and microfluidic nanoprecipitation (MNP) were investigated in comparison to batch nanoprecipitation (BNP) in order to demonstrate the potential for scale-up processing of SNPs. Under the same processing conditions, FNP yielded a more uniform spherically shaped SNPs with a particle size of ~100 nm, which was superior to all other techniques investigated. The Pickering emulsion produced using SNPs obtained by FNP had a smaller average droplet size of 3 μm when compared to emulsions produced without SNPs, which had an average size of 200 μm. With respect to phosphorylation of pulse starches and its impact on starch properties, the results indicated that this chemical modification significantly altered the thermal stability, crystallinity, flow behavior and amylase resistance of pulse starches. Overall, this research addresses the significant gap in the literature regarding pulse starch nanoparticulation and chemical modification/phosphorylation, and how these processing techniques would alter the physicochemical properties of native pulse starches. Developing such novel applications to pulse starches by nanoparticulation and chemical modification is expected to enhance the sustainability of the pulse grain processing industry.