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In recent years, there has been a growing interest within the field of soft materials engineering on the development of advanced hydrogel systems with well-defined chemistries and morphologies that can be customized to suit various applications ranging from biomedical to environmental to personal care. In any case, careful selection of the building block materials, crosslinking chemistry, degradation pathway, and overall hydrogel architecture is essential to ensure the final design (and the resulting degradation components if relevant) are safe/non-toxic, mechanically tunable, and overall translatable for their intended end use given industry safety/production standards. In this thesis, the utility of starch nanoparticles created by a reactive extrusion process was explored as one such building block for creating renewable hydrogels. Starch was reactively extruded by EcoSynthetix Inc. to create starch nanoparticles (SNPs) that are attractive as hydrogel building blocks due to their inherent small size (25-50 nm), generally safe degradation products, overall net neutral charge, high deformability/viscoelastic properties, stability in solution without collapsing or changing size (on the order of months), and the ability to be manufactured at a multiple kg/hr rate; in comparison, other manufacturing methods of SNPs suffer from a lack of scalability or require the use of potentially toxic solvents, making them less amenable to biological or environmental/agricultural applications. The amorphous nature of the starch also allows for facile functionalization to further chemically modify and/or crosslink the SNPs through surface functional group (i.e. hydroxyl) modification chemistries. The nanoparticle nature of the SNP building block, coupled with the facile functionalizability of the SNPs, also makes SNPs ideal building blocks for the design and fabrication of nanoparticle network hydrogels (NNHs) in which NPs create an interconnected network on their own on, in addition to, other polymeric networks at any desired length scale. There are a variety of NNH architectures that can be achieved through careful design considerations. More specifically, herein colloidal NNHs were created using UV photopolymerization post-functionalization with methacrylic anhydride, which leaves a vinyl group on the SNP surface. Alternately, plum pudding NNHs were created by mixing aldehyde-functionalized SNPs with amine-bearing O-carboxymethyl chitosan that were able to chemically react via hydrolytically labile imine bonds. The properties of various types of colloidal and plum-pudding hydrogels based on SNPs were tested and subsequently compared through a range of different performance tests such as rheological and micromechanical force testing, swelling/degradation kinetics, their potential for controlled bioactive release, and overall toxicity (cell and organ level). In addition to these macroscopic performance tests, the internal morphologies of both colloidal and plum pudding NNHs were assessed with small angle and very small angle neutron scattering experiments to glean insight into how these internal structures correlate to macroscopic properties. For all experiments, the effect of using SNPs versus typical cold water-soluble branched starch (SS) was assessed to further understand the impact of making hydrogels from nanoscale rather than soluble polymer building blocks, with the small size of SNPs compared to the large hydrodynamic radius of SS consistently allowing for greater control over the range of potential hydrogel properties. The results of these studies suggest that SNP-based NNHs are promising materials for studying the encapsulation and release of small molecules in both in vitro and in vivo settings. For example, the photopolymerization of methacrylated SNP-based NNH coatings can be fabricated at much higher concentrations than possible with conventional starch (35% for SNP, 10% for SS), leading to denser and stiffer gels compared to SS controls albeit with slightly longer gelation times due to the reduced conformational mobility of the polymerizable methacrylate groups on the SNPs. The addition of charge (cationic or anionic) to the SNP surface further increases the bulk gelation time while significantly reducing the observed changes in SNP deformation during photogelation as confirmed via very small angle neutron scattering experiments. Other functional groups were also demonstrated to be introduced to SNPs to enable different types of gelation for different applications. For example, in situ-gelling and degradable bulk nanoparticle network hydrogels consisting of oxidized starch nanoparticles (SNPs) and carboxymethyl chitosan (CMCh) were created for intranasal delivery that could be delivered into the nose via a commercial atomization device to enable high nasal mucosal retention and functional controlled release of the peptide drug PAOPA, a positive allosteric modulator of dopamine D2 receptor. Selected gels shown to alleviate negative behavioural abnormalities associated with for up to 72 hours in pre-clinical rat models of schizophrenia at a low drug dosage (0.5 mg/kg), compared to just a few hours with the drug alone. Finally, the functionalization of SNPs with hydrophobic groups (via grafting the starch with octenyl succinic acid (OSAn) or succinic anhydride (SAn)) was demonstrated as a promising delivery system for agricultural applications. Hydrophobization increased the contact angle of a sprayed watermelon and pumpkin leaves from <60˚ (unmodified) to ~80˚ when modified (DS 0.25), while confocal fluorescence microscopy confirmed that the hydrophobized SNPs can both adhere to the leaf surface as well as penetrate into the leaves when sprayed due to their small size (25-50 nm). Future work will look at other methods of crosslinking SNPs (i.e. Michael addition, hydrazone, and alkyne-azide “click” chemistry, amongst others) to see if there are beneficial differences compared to analogous hydrogels made from macroscopic alternatives (i.e. polymers alone) and to follow-up the findings already gleaned within this thesis. Further information on the impact and potential follow-up experiments for the work conducted in this thesis will be explained in Chapter 6 on final outlooks and conclusions of the following work. / Thesis / Doctor of Philosophy (PhD) / This thesis describes the chemical and physical modification of commercially-available starch nanoparticles (SNPs) to rationally create novel hydrogel systems. These gel-like networks are made by chemically connecting starch nanoparticles (with sizes on the 10-8 m length scale) by introducing various reactive chemical groups onto the surface of SNPs, enabling the creation of hydrogels with well-defined structures, features, and properties. Careful selection of the crosslinking chemistry made it possible to tune hydrogel properties to specific application requirements, such as the targeted delivery of pharmaceuticals (including the intranasal delivery of antipsychotic drugs to the brain, a key technical challenge to improve the quality of life of patients with mental health challenges) and agrochemical agents or as an anti-fouling coating. The hydrogels created herein are attractive since they directly incorporate nanoscale particles generated from a sustainable source and are generally regarded as safe (GRAS) in terms of their degradation products once they break down, a rare trait for nanoparticles of this size. The existing industrial-scale production of the SNPs also enables facile scaling of these strategies for ultimate commercial translation.

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No description available.

Apple preharvest fruit drop frequently results in severe economic losses. Cultural control of preharvest drop has relied upon plant growth regulators (PGRs), but the loss of daminozide (Alar) and 2,4,5-TP has severely limited the choices of effective stop-drop compounds. A more complete understanding of factors involved in preharvest drop is therefore imperative. Experiments were conducted to provide information about cellulase activity in the abscission zone, effects of applied auxin and ethylene biosynthesis inhibition on drop, changing sensitivity to abscission induction during the season, and relationships among seed number, fruit weight, and day of drop. Observational studies were used to study effects of fruit maturity, canopy positions, and morphology of stem attachment on time of fruit drop as well as characterizing the natural timing of late-season fruit drop. Increased activity of cellulase, but not polygalacturonase, in the abscission zone was detected within 4 days of cutting fruit to induce abscission. Both aminoethoxyvinyl glycine (AVG) and naphthaleneacetic acid (NAA) applied 2 or 4 days after cutting delayed drop, but NAA delayed drop 1.6 days longer than did AVG. Fruit of "RedChief Delicious"(D) exhibited a significantly reduced sensitivity to abscission-inducing treatments from mid-June until early July compared to earlier orr later in the season. Application of plant growth regulators to cut fruit revealed a significant interaction of NAA treatment with AVG treatment such that NAA delayed drop when applied with AVG but not without AVG. Fallen fruit had lower starch and higher soluble solids than fruit on the tree on the day of collection. The highest fruit in the canopy fell an average of 4.4d earlier than the lowest fruit. Day of drop was not different for fruit from king blooms vs. side blooms within an inflorescence. There was a trend for fruit from first year wood to drop later than fruit from older wood on "Delicious", but not "Smoothee Golden Delicious" trees. There was no detectable effect of angle of orientation of the subtending spur on the limb, the pedicel:spur abscission zone, or fruit axis of symmetry on time of fruit drop. No difference was detected in time of fruit drop between East and West or North and South sides of the trees. No substantial variation in day of drop of individual fruit was explained by number of seed in the fruit. Daily drop was recorded for three cultivars ("RedChief Delicious", "Smoothee Golden Delicious", and "Commander York") for three years. Variance of average day of drop from year to year was 40.1, while variance among cultivars within a year was 51.8. Variance from tree to tree within each cultivar, within each year, was only 18.6. Multiple regression modeling to identify relationships between weather factors and daily fruit drop revealed that much of the variability in time of drop was due to factors other than the weather events modeled. The best regression models developed explained only 8% to 35% of the variability in time of drop. The most important weather factors were daily minimum temperatures and precipitation. Rain events of greater than 5.0 mm following a drier period appeared to cause increased drop of all three cultivars in one out of the three years investigated. / Ph. D.

The suitability of powdered starch with borax or glycerine accessories for dark cottons of three different colors and weights and with selected construction gestures was ascertained. Selected colors, weights, and construction features were evaluated by analysis of variance for their effect on the suitability of the starch and its additive. The scores recorded by a panel of competent judges supplied data on the change in color, luster, and hand of the starched fabric. The color was statistically significant in only half of the instances for which it was analyzed. The weight of the fabric was significant for one-fourth of the starched samples. Construction influenced starching only when combined with another factor, and then is only one case of a possible six. Scores indicated starching caused from moderate to considerable change for the majority of the samples. The glycerine and starch treatment was more affective than the starch and borax combination. / M.S.

The effects of starch-based anti-caking agents on the browning of Mozzarella cheese were evaluated in this experiment. Six commercially available anti-caking agent treatments were examined and color measurements indicated that the starch-based anti-caking agents produced a baked cheese with a greater degree of browning than the samples treated with cellulose based anti-caking agents or no treatment (control). The cellulose-based treatments and the control also had a significantly greater moisture loss than the potato starch-based treatments. A negative correlation between percent moisture loss and the amount of browning was found (R2=0.51). The average surface temperature was at least 16 °C higher for the treatments containing potato starch than for the cellulose-based treatments. A significant relationship between average surface temperature and browning was also found (R2=0.67). These relationships suggest that the starch-based treatments impeded moisture loss, which decreased the amount of evaporative cooling. An increase in surface temperature resulted from the decrease in the amount of evaporative cooling and thus the Maillard reaction was accelerated leading to increased browning. The effects of the starch source were examined using starches from corn, rice and wheat. These starches were compared to commercially available potato starch and cellulose anti-caking agents. All starch sources were found to produce a greater degree of browning on the cheese sample compared to the cellulose treatment and control. Four adjuncts treatments, including dimethypolysiloxane, lactic acid, partially hydrogenated sunflower oil, and a combination of the dimethylpolysiloxane and sunflower oil were added to cheese treated with potato starch to determine if a reduction in the degree of browning could be achieved. No differences in browning between the potato starch treatment and those with added adjuncts were found. / Master of Science

The effects of starch and phosphorus (P) source on P partitioning and ruminal phytase activity were evaluated in eight lactating cows (113 DIM). Four cows were ruminaly cannulated. Cows were randomly assigned to treatments in a duplicated 4x4 Latin square with four, 18-d periods. Diets included dry ground corn (DG) or steam flaked corn (SF), with a no supplemental P (low P diet; 0.34% P) or supplemental purified phytic acid (PA; 0.45% P) to provide additional P from an organic source. Total collection of milk, urine, feces, and feed were sampled each period, while rumen fluid was sampled on d 18. Excretion of feces, urine, P, and N was lower in cows fed SF than in cows fed DG. Milk yield was unaffected by diet despite a lower DMI by cows fed SF. Cows fed SF tended to have a higher feed efficiency and lower milk urea nitrogen (MUN) concentration than cows fed DG. Rumen pH was unaffected by diet, but milk fat content was lower for cows fed SF. Milk yield, DMI, and feed efficiency were not affected by PA. Cows fed PA had increased P intake and excretion, but a lower milk P as a percentage of intake compared with cows fed the low P diet. An interaction of starch source and P source was observed for ruminal phytase activity. Altering dietary sources of starch and P offers opportunity to improve P availability and reduce manure nutrient excretion. / Master of Science

Mozzarella cheese production has been gaining market share due in part to increasing market for pizza and ready to eat food items. Anti-caking agents are utilized in the production of shredded cheese for reducing clumping and increasing the appearance of separate cheese shreds. Six anti-caking agents were applied to low moisture part skim Mozzarella cheese and examined for effects on three major functional properties of Mozzarella cheese; meltability, stretchability, and free oil formation. Meltability determination utilizing a fabricated UW Meltmeter resulted in no significant differences between untreated samples (control) and samples treated with anti-caking agents containing cellulose, potato starch or mixtures including dextrose. Stretchability measurements taken using a modified helical viscometry procedure also resulted in no significant differences between control and treated samples. Significant differences were found when comparing free oil percentages obtained from varying treatments of anti-caking agents. A mixture of potato starch and cellulose resulted in the lowest level of free oil among all samples tested. Because potato starch treated samples performed equally to cellulose treated samples in both meltability and stretchability testing, anti-caking agents containing potato starch could be considered as an alternative to cellulose-based anti-caking agents. In addition, the use of potato starch alone and in conjunction with powdered cellulose has been shown to be more effective for free oil control. By treating with potato starch, functional properties of shredded Mozzarella cheese have been positively altered in a way which may increase acceptability by consumers. / Master of Science