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High amylose cornstarch, normal cornstarch and waxy cornstarch were plasticized using water and glycerol as plasticizers in a Haake Rheomix 3000 batch mixer. A two-level factorial experiment design was used to investigate the effects of processing conditions and the water/glycerol ratio on the mechanical properties of the thermoplastic starches. The significances of factors (processing temperature, time, roller rolling rate and ratio of water to glycerol) on the mechanical properties were evaluated. The morphology, thermal properties, average molecular weight and molecular weight distribution of the thermoplastic starches were analyzed using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and high performance size exclusion chromatography (HPSEC). The mechanical properties and rheological properties of the materials were measured using an Instron tensile testing machine and a Rosand capillary rheometer. The thermoplastic starches were further blended with poly(lactic acid)(PLA) at different composition ratios. The morphology, thermal properties, molecular weight and molecular weight distribution of the thermoplastic starch/PLA blends were analyzed using SEM, DSC, HPSEC. Mechanical and rheological properties of the blends were investigated using the same methods as those used in the investigation of thermoplastic starches. The effects of amylose content in the starches, composition (starch/plasticizer ratio, water/glycerol ratio, starch/PLA ratio), molding methods and molding temperature on structure and properties of thermoplastic starches and thermoplastic starch/PLA blends were also investigated and compared. A power law model and a cross model were used to fit the experimental rheological data of the thermoplastic starches and the thermoplastic starch/PLA blends. The thermoplastic normal starch with starch/plasticizer ratio of 2/1 (wt/wt%) shows a tensile strength of 2.81 MPa, a modulus of 55.09MPa and an elongation at break of 76.0%. The post-extruded thermoplastic normal starch/PLA blend with the starch/PLA ratio of 50/50 (wt/wt) and the starch/plasticizer ratio of 2/1(wt/wt) exhibits a tensile strength of 15 MPa, a modulus of 926 MPa and an elongation at break of 6%. / Thesis / Master of Applied Science (MASc)

Grain quality in chickpea (<i>Cicer arietinum</i> L.) is a major factor affecting its consumption for human nutrition and health benefits. Some of the major factors affecting chickpea grain quality are: seed weight, size, colour, protein, starch and amylose concentration, and amylopectin structure. The objectives of this study were to: 1) determine variation, repeatability and genotype by environment interaction on thousand seed weight, starch, amylose and protein concentration of chickpea cultivars adapted to western Canada; 2) assess variations in global chickpea germplasm for thousand seed weight, seed size, protein, starch and amylose concentrations; and 3) characterize the desi and kabuli type chickpea for starch concentration, composition, and amylopectin structure to study their effect on starch enzymatic hydrolysis. Limited variation was observed in seed composition of chickpea cultivars adapted to the western Canadian prairies. Significant genotype by environment interaction occurred for starch, amylose, and protein (except for kabuli) concentrations, seed yield and thousand seed weight indicating that testing over a wide range of environments is needed to identify genotypes for grain quality improvement. Repeatability of starch, amylose, and protein concentrations was low and inconsistent across chickpea market classes. Broad sense heritability was higher than repeatability across all traits for all market classes implying that repeatability estimates do not set upper limits to heritability if significant genotype by environment interaction is present. The negative relationship between seed constituents and yield indicates that selection for chickpea cultivars with desired seed composition may require compromise with yield and indirect selection. All the mini core accessions that had above average seed diameter score in both desi and kabuli also had above average score for thousand seed weight. Selecting mini core with promising intrinsic and extrinsic quality characteristics may reduce yield. Slowly digestible starch was negatively correlated with hydrolysis index in both pure starch and meal starch of desi and kabuli. Amylose had a strong relationship with resistant starch but not with rate of starch hydrolysis. Genotypes with a significantly higher rate of starch hydrolysis had significantly lower 60-80 µm starch granule size volume. Amylopectin B2 chains were related to slowly digestible starch of meal (except kabuli) and extracted starch. Resistant starch positively correlated with B1 fraction of amylopectin chain length in both desi and kabuli meal starch. Our results suggest that there is no major difference between starch composition in the two chickpea market classes, although only three genotypes of each class were tested. The meal components affect the starch hydrolytic properties and the effect is genotype specific. The results also show that amylopectin structure influences starch hydrolytic properties. These observations emphasize that complete characterization of seed components is needed to obtain meaningful results regarding the desired nutritional and health benefits attributed to any grain.

Grain quality in chickpea (<i>Cicer arietinum</i> L.) is a major factor affecting its consumption for human nutrition and health benefits. Some of the major factors affecting chickpea grain quality are: seed weight, size, colour, protein, starch and amylose concentration, and amylopectin structure. The objectives of this study were to: 1) determine variation, repeatability and genotype by environment interaction on thousand seed weight, starch, amylose and protein concentration of chickpea cultivars adapted to western Canada; 2) assess variations in global chickpea germplasm for thousand seed weight, seed size, protein, starch and amylose concentrations; and 3) characterize the desi and kabuli type chickpea for starch concentration, composition, and amylopectin structure to study their effect on starch enzymatic hydrolysis. Limited variation was observed in seed composition of chickpea cultivars adapted to the western Canadian prairies. Significant genotype by environment interaction occurred for starch, amylose, and protein (except for kabuli) concentrations, seed yield and thousand seed weight indicating that testing over a wide range of environments is needed to identify genotypes for grain quality improvement. Repeatability of starch, amylose, and protein concentrations was low and inconsistent across chickpea market classes. Broad sense heritability was higher than repeatability across all traits for all market classes implying that repeatability estimates do not set upper limits to heritability if significant genotype by environment interaction is present. The negative relationship between seed constituents and yield indicates that selection for chickpea cultivars with desired seed composition may require compromise with yield and indirect selection. All the mini core accessions that had above average seed diameter score in both desi and kabuli also had above average score for thousand seed weight. Selecting mini core with promising intrinsic and extrinsic quality characteristics may reduce yield. Slowly digestible starch was negatively correlated with hydrolysis index in both pure starch and meal starch of desi and kabuli. Amylose had a strong relationship with resistant starch but not with rate of starch hydrolysis. Genotypes with a significantly higher rate of starch hydrolysis had significantly lower 60-80 µm starch granule size volume. Amylopectin B2 chains were related to slowly digestible starch of meal (except kabuli) and extracted starch. Resistant starch positively correlated with B1 fraction of amylopectin chain length in both desi and kabuli meal starch. Our results suggest that there is no major difference between starch composition in the two chickpea market classes, although only three genotypes of each class were tested. The meal components affect the starch hydrolytic properties and the effect is genotype specific. The results also show that amylopectin structure influences starch hydrolytic properties. These observations emphasize that complete characterization of seed components is needed to obtain meaningful results regarding the desired nutritional and health benefits attributed to any grain.

Storage starch is synthesized in sub-cellular organelles called amyloplasts in higher plants. The synthesis of the starch granule is a result of the coordinated activity of several groups of starch biosynthetic enzymes. There are four major groups of these enzymes, ADP-glucose pyrophosphorylase (AGPase), starch synthases (SS), starch branching enzymes (SBE), and starch debranching enzymes (SDE). Starch phosphorylase (SP) exists as both dimeric and tetrameric forms in plastids in developing cereal endosperm and catalyses the reversible transfer of glucosyl units from glucose-1-phosphate to the non-reducing end of α-1-4 linked glucan chains, although the precise role in the pathway remains unclear. The present study was conducted to investigate the role and regulation of SP and SSIV in starch biosynthesis in developing maize endosperm. The results of this study showed that the tetrameric form of SP accounts for the majority of measurable catalytic activity, with the dimeric form being barely active and the monomer catalytically inactive. A catalytically active recombinant maize SP was heterologously expressed and used as an affinity ligand with amyloplast lysates to test protein-protein interactions in vitro. Results showed that the different multimeric status of SP influenced interactions with other enzymes of starch synthesis. Tetrameric SP interacted with SBEI and SSIIa, whilst the dimeric form of the enzyme interacted with SBEI, SBEIIb. All of these interactions were enhanced when amyloplasts were pre-treated with ATP, and broken following treatment with alkaline phosphatase (APase), indicating these interactions are regulated by protein phosphorylation. In addition, the catalytic activity of SSIV was reduced following treatment with APase, indicating a role for protein phosphorylation in the regulation of SSIV activity. Protein-protein interaction experiments also suggested a weak interaction between SSIV and SP. Multimeric forms of SP regulated by protein-protein interactions and protein phosphorylation suggested a role for SP in starch biosynthesis in maize endosperm.

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Starch is an attractive raw material for biodegradable plastic applications due to its low cost, its availability in large quantities and its excellent thermal process-ability using conventional plastic processing equipments. Despite its attractive potential as a biopolymer material, the use of starch in biodegradable plastic applications is yet limited by its structural and functional properties, which are dictated by its genetic make up. This dissertation involves in-depth characterisations of a range of biotechnologically derived novel starches from different cereal sources to elucidate the relationship between starch structure and functionality. The importance of understanding starch structure-functionality relationship to further the development of starch biodegradable plastics are discussed to identify the research questions, which underlie the motivation of this dissertation and to contextualize the objectives of this dissertation. Diversities in starch macromolecular properties namely the amylose content and amylopectin chain length distribution are evident in these novel starches. The variation in amylopectin structure in these novel starches is explicable by considering the particular inhibition of starch biosynthesis gene expression in the generation of these starch mutants. Amylose content and amylopectin chain length distribution are two separate structural parameters in starch, which influence the granular and functional properties of starch. An improved method to analyse the 13C solid state NMR spectra for native starches was developed in this dissertation and provides the first elucidation on the occurrence of V-type polymorph, which is significant in high amylose starches. An increase in starch amylose content (or decrease in amylopectin content) leads to a decrease in the double helix content and crystallinity. A transition in the double helical packing arrangement of amylopectin side chains from A-type to B-type polymorph is noted for high amylose starches. This can be attributed to the changes in their amylopectin chain length distribution, which leads to the tendency of the glucan chains to form the B-type polymorph during crystallisation from thermodynamic considerations. The application of MTDSC provides the first elucidation on the step transition or heat capacity change, which is noted to occur within the gelatinisation endotherm for all starches. The use of Rheoscope, which allows for simultaneous monitoring of the changes in starch granular and rheological properties during gelatinisation, reveals that the manifested changes in viscosity can be attributed to the increase in the granules size as a result of swelling, the change in granules properties from rigid to more deformable granules due to water penetration and the increase in the viscosity of the continuous phase due to leaching of amylose. The variation in starch gelatinisation thermal properties namely the onset temperature, enthalpy and heat capacity change can be attributed to the variation in amylopectin chain length distribution, amylose content and the amount of starch structural order. A reduction in swelling power with increasing amylose content is consistently noted for all starch types. The variation in starch rheological responses during gelatinisation can be mainly attributed to the swelling ability of starch granules and their granule size distribution (to a lesser extent). Further MTDSC investigations on starch gelatinisation in the presence of water and glycerol with different concentrations indicate that plasticisation of starch granules prior to gelatinisation does not occur. The observed mid-temperature of the step transition (heat capacity change) is more likely due to a change in state of the starch macromolecules from being highly restrained within the granular packing to entangled macromolecules (as the order to disorder transition occurs) rather than due to glass transition. The addition of glycerol promotes starch gelatinisation in a similar way as the addition of water, which suggests that the same structural changes occur during gelatinisation regardless of the solvents used. In summary, the following starch structure-functionality relationships are deduced. The variation in starch macromolecular properties can be attributed to their corresponding mutation of starch biosynthetic genes expression. The variation in starch amylose content affects the extent of structural order inside the granules while the double helix packing arrangement is influenced by the amylopectin chain length distribution. Starch gelatinisation thermal properties are mainly influenced by the amylopectin chain length distribution while the swelling power and rheological properties are mainly affected by the amylose content.

<div>Starch pasting behavior greatly influences the texture of a variety of food products such as canned soup, sauces, baby foods, batter mixes etc. The annual consumption of starch in the U.S. is 3 million metric tons. It is important to characterize the relationship between the structure, composition and architecture of the starch granules with its pasting behavior in order to arrive at a rational methodology to design modified starch of desirable digestion rate and texture. </div><div> In this research, polymer solution theory was applied to predict the evolution of average granule size of starch at different heating temperatures in terms of its molecular weight, second virial coefficient extent of cross-link and electrostatic interaction within a granule. Evolution of granule size distribution of normal maize starch (NMS) and NMS crosslinked to different extents with sodium trimetaphosphate, waxy rice starch, normal rice starch and normal potato starch when subjected to heating at a rate of 15 C/min to 65, 70, 75, 80, 85 and 90 C was characterized using static laser light scattering. As expected, granule swelling was more pronounced at higher temperatures and resulted in a shift of granule size distribution to larger sizes. Most of the swelling occurred within the first 10 min of heating except for potato starch. Novation 1600 (Modified Potato Starch) is also found to shift to larger sizes at longer holding times and higher temperatures, but this shift is found to be gradual and for penpure 80, even at 60 C, the size distribution shifts to smaller sizes at longer holding times indicating breakup of the granule. </div><div> The structure of normal maize starch was characterized by cryo scanning electron microscopy. The number of crosslinks in the starch network was inferred from equilibrium swelling. This is related to peak viscosity and zeta potential of granule for NMS and its crosslinked starches. Chemical potential profile as well as the temperature profile within the granule at different times were predicted which were then employed to evaluate the granule size at different times. The proposed model is able to describe the swelling behavior of different varieties of starch and also the effect of crosslinking. </div><div> The viscoelasticity for different starch types, heating rates, and heating temperatures were characterized. A methodology to predict the storage modulus of starch paste due to granule swelling, given the physical properties of the starch granule is presented. In high-volume fraction regime, classical model for foam rheology enabled calculation of limiting storage modulus for different starches. By scaling the storage modulus with limiting storage modulus, the storage modulus of a wide range of starches forms a master curve. This master curve when employed along with the swelling model resulted in the successful prediction of development of texture for different types of starches. </div><div> In low-volume fraction regime (below 65%), Stokesian dynamics simulations are used to predict the viscoelasticity of polystyrene micro particles and fractionated starch suspension and compared with experiments. Predicted values of storage modulus from stokesian dynamics simulation at 4 HZ for different volume fractions of monodispersed polystyrene spheres of two different sizes namely 25 and 116 micrometer compared well with experimental values. Stokesian dynamics also describes the storage modulus of fractionated starch granules for volume fractions between 0.4 - 0.5</div><div> The average granule size of starch in presence of sucrose was initially increasing and then decreasing with maximum swelling at 5% and 10% sucrose concentration for NMS and WRS. The average granules size continuously increases for WMS and decreases for NRS with increase in sucrose concentration. The Gelatinization Temperature increases with increase in sucrose concentration for all starches. Enthalpy of Gelatinization increases with increase in sucrose concentration for Normal starches where as there is no effect of sucrose concentration for waxy starches. Flory Huggins starch-sucrose interaction parameter was characterized which is used to predict the equilibrium swelling power using a mathematical model proposed to quantitatively describe the equilibrium swelling in the presence of solute (sucrose) based on Flory Huggins polymer solution theory to develop rational guidelines for identification of sugar substitute with desirable functional properties. The model predictions of equilibrium swelling power agrees with experimental results.</div>

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