In this study, a mutant of the yeast Saccharomyces cerevisiae was used for the selective conversion of glucose to ethanol using feed solutions of sucrose. Batch fermentation using 30% (w/v) sucrose without membrane separation of ethanol required about 27 hours for glucose to be decreased to 2% (w/v), with a fructose yield of 99%, and an ethanol yield of 78%. Batch fermentation using 30% (w/v) sucrose with membrane separation of ethanol required about 16.5 hours for glucose to be decreased to 2% (w/v), with a fructose yield of 96.5% and an ethanol yield of 79.5%, if the membrane was started after 6 hours of batch mode. The process required about 15 hours if the membrane was started after 3 hours of batch mode, with a fructose yield of 92%, and an ethanol yield of 82%. In fed-batch mode the yeast was able to process the equivalent of a 40% (w/v) sucrose feed in 24 hours, compared to well over 40 hours without ethanol removal, with yields of, 98% fructose, and 82% ethanol. (Abstract shortened by UMI.)

This research project was focused on the development of a novel enzymatic method for upgrading commercial canola meal by decreasing its phenolic content. The new method is based on the enzymatic transformations of sinapic acid esters (SAE) and free sinapic acid (SA), the two main constituents of the phenolic fraction of canola meal (CM), using an enzyme preparation secreted by the white-rot fungi Trametes versicolor ATCC 42530. The study was divided into three parts: (1) enzyme production; (2) characterization of the enzyme produced--a model enzymatic system; (3) enzymatic upgrading of commercial canola meal--a canola meal system. The enzyme preparation produced was characterized in the model enzymatic system using sinapic acid (SA), sinapine (SIN) and sinapaldehyde (SALD). The results showed that the enzyme is inhibited by high concentrations of SIN and SA. Depending on the substrate, the optima temperatures and pH are in the range of 50$\sp\circ$C-60$\sp\circ$C and 3.3-4.5, respectively. The enzyme was very thermostable; the maximum thermal stability was noticed at pH values between 4.5 and 6.5. Sodium azide was a strong inhibitor of this enzyme while its activity was not affected by EDTA. Based upon the results obtained, the enzyme was characterized as a polyphenol oxidase. The overall transformation of SA was described by a mathematical model based on the Theorell-Chance Bi-Bi mechanism with oxygen as the first substrate, and the second substrate being one of the alternate phenolic compounds: SA, DAD and the unknown compound formed via the thermolysis of DAD. The modeling of sinapine transformation was also considered in this work. A mechanistic model, based on the Theorell-Chance Bi-Bi mechanism, that simultaneously predicted the effects of the concentrations of the enzyme, SIN and oxygen, for any given pH and temperature level, on the rates of the enzymatic reaction was formulated. The model parameters were estimated following the new procedure developed in this work for analyzing data concerning the effects of pH and temperature on enzyme activity. The formula relating the optimum pH of the reaction with the temperature was proposed. The enzyme preparation produced and subsequently characterized was used in the novel method to decrease the phenolic content in commercial CM, which was based on the addition of the enzyme to the meal-buffer slurry. It was found that: (1) the natural buffering capacity of CM resulted in the negligible effect of the pH of the buffer, which was used as the continuous phase in the process, on the extent of SAE decrease; (2) the system was saturated with the enzyme when the enzyme concentration was 4 nkat per mL of the continuous phase; (3) the optimum temperature was 50$\sp\circ$C. (Abstract shortened by UMI.)

Solids puff when unbalanced forces exerted by vapor and gas in pores exceed the yield strength of solid surrounding the pores. Pressures increase as temperature rise; and matrix yield strength and flow resistance decrease. Expansion triggered by losses of matrix strength due to melting and glass-rubber transitions occurs. Water-loss and evaporative cooling induce reversal of these processes and stabilize expanded products so that they do not collapse after heating is stopped. Water sorption behaviors for corn starch and popcorn grits between 100 and 180$\sp\circ$C were measured at various moisture contents. Pressures inside popcorn at the instant of popping are roughly 110 to 120 psia. Non-condensible gases were produced by heating popcorn grits to 150 and 180$\sp\circ$C. At 180$\sp\circ$C, corn starch turns into a brown, sticky liquid. Heats of sorption for corn starch were estimated, and changed significantly with moisture content and temperature. Popping temperatures of popcorn in 200$\sp\circ$C air inversely correlated with initial moisture content. Temperatures dropped at popping in the range of 5.4-6.2$\sp\circ$C. DSC was used to detect and measure phase transition between 40 and 250$\sp\circ$C for corn starch and popcorn grits. Corn starch and popcorn grits melt between 160 and 240$\sp\circ$C, and the melting temperature decrease and amount of heat absorbed during melting increase as moisture content increase. Coating popcorn with zein slightly reduced rates of moisture loss during heating. Expansion bulk volumes increased 15% for coated popcorn and the unpopped ratio decreased slightly, but only when the popcorn popper was not preheated. Expansion volume didn't increase significantly when the popper was preheated. Zein coating did not significantly improve expansion bulk volume and unpopped ratios for samples with damaged pericarp. Expansion ratios, extents of evaporation, puffing temperatures, pore characteristics, and heating-induced enthalpy changes were measured versus temperature and moisture content for popcorn, and used to identify conditions that induce puffing, and levels of moisture loss needed to stabilize puffed structures. Puffing probably initially occurs through expansion of vapor trapped in individual grain of starch. Pore walls rupture and pores merge when excessive vaporization occurs. Pore openness of popped popcorn increases linearly with initial moisture contents.

The objective of this research was to examine and investigate the stabilization of $\beta$-galactosidase by histidine. Of the four $\beta$-galactosidases tested, histidine stabilized the enzyme from Kluyveromyces marxianus more than the enzyme from Streptococcus thermophilus, Escherichia coli or Aspergillus niger. The enzyme from K. marxianus was purified to electrophoretic homogeneity on a non-denaturing PAGE (pH 8.0) and its kinetic stability determined at 45$\sp\circ$C. All the twenty amino acids (1 mM) tested, except proline, stabilized the enzyme. Histidine was the most effective stabilizer. It enhanced the half-life of the enzyme 58-fold in the presence of 5% lactose. Increasing the lactose concentration up to 15% increased histidine stabilization. Glucose and maltose did not affect the histidine stabilization while galactose and sucrose enhanced it. Histidine also stabilized the enzyme in the absence of sugars but to a lesser extent. The $\alpha$-amino group and the N-1 nitrogen on the imidazole ring of histidine were essential for histidine stabilization while the carboxylic group played a role in the extent of stabilization. Histidine stabilization decreased with increasing ionic strength. The energy of activation for inactivation of this enzyme in the temperature range of 45 to 51$\sp\circ$C was unaffected by histidine. Binding of histidine to the enzyme was not observed by equilibrium dialysis and gel filtration experiments. Further, the melting temperature (51.4$\sp\circ$C) of the enzyme as detected by differential scanning calorimetry was not affected by histidine. Under isothermal conditions a delay in unfolding of the enzyme in the presence of histidine was observed by absorbance spectroscopy. The delay was temperature dependent and was not detected at 47.5$\sp\circ$C. Histidine is probably acting in the inital stages of unfolding on a partially unfolded molecule but the nature of its action is not completely understood. Lactose alone, delayed the unfolding and increased the melting temperature but did not effectively enhance the half-life of the enzyme. The K$\sb{\rm m}$ for lactose and the apparent binding constant for magnesium were unaffected by histidine. Histidine increased the half-life of this enzyme by 44% in milk at 45$\sp\circ$C but was not effective in milk ultrafiltrate.

This work focused on the effect of pH on the solubilization, water-uptake and gelation of myofibrillar proteins at reduced salt concentrations (≤150 mM). Solubilization of myofibrillar proteins in water was affected by certain possible solubility-inhibiting (PSI) polypeptides and postmortem exposure to a low pH. These PSI polypeptides might act like a binder that prevented the rest of the myofibrillar proteins from disorganization, swelling and subsequent solubilization in water. M-protein (166 kDa), a-actinin (95 kDa) and desmin (56 kDa) were tentatively identified as the PSI polypeptides in the mackerel light muscle. Exposure of myofibrillar proteins to the low pH that accompanies postmortem glycolysis could cause protein denaturation and subsequently the loss of extractability in water. However, over 96% of muscle proteins were solubilized after a pre-wash in a solution of physiological ionic strength at neutral pH. The water-uptake of twice water-washed minced chicken breast muscle at physiological ionic strength was governed by the balance between the driving forces for, and the constraint components against, swelling. pH adjustment from 6.4 to 7.0 increased electrostatic repulsive forces and the osmotic potential of myofibrillar proteins. It also solubilized the constraint components associated with myofibrillar structure. Therefore, it increased the water-uptake. pH adjustment from 6.4 to neutrality improved the gel strength and water-holding capacity significantly. After pH adjustment, the net negative charges of muscle proteins increased; the proteins unfolded more extensively during the heating process. Gels formed at physiological ionic strength consisted of mainly myofibrils. These myofibrils, which tended to form a network of localized aggregates at pH 6.4, formed a more evenly distributed network of myofibrils at neutral pH. Cell segments were capable of expansion before gelation (40–50°C) at neutral pH and their final volumes after heating were larger than those at pH 6.4. The thick filaments formed a porous network within the myofibrillar structure at neutral pH. During the cooling process, the gel strength was improved more at neutral pH than at pH 6.4. Structural disorganization imposed by pH adjustment from 6.4 to 7.0 was found not sufficient to improve the gelation significantly. It is suggested that pH adjustment from 6.4 to 7.0 introduced several favorable effects for gelation and water-holding capacity.

Electrospun nanofibers have improved physicochemical properties compared to macroscalar fibers and are therefore increasingly investigated for use in novel food packaging systems. The objectives of this study were to electrospin nanofibers and to evaluate the effect and feasibility of surfactants and surfactant aggregates to modulate properties and functionalities of electrospun nanofibers. Nanofibers were fabricated by electrospinning a mixture of cationic chitosan and noncharged poly(ethylene oxide) (PEO) in aqueous acetic acid. To improve spinnability and nanofiber morphologies, surfactants were added to biopolymer/polymer solutions and their influence was investigated. Solution properties were evaluated by rheological, surface tension, and conductivity measurements. Fibers were characterized by scanning and transmission electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Addition of PEO and surfactants induced spinnability producing larger fibers with diameters ranging from 40 to 240 nm, while pure chitosan did not form fibers and was instead deposited as beads. Compositional analysis suggested that nanofibers consisted of all solution constituents with chitosan concentrations being significantly lower in fibers than in solution, indicating that surfactants may have decreased polymer-polymer interactions responsible for entanglement. Poly(vinyl alcohol) nanofibers were used as novel delivery system for eugenol carrying Surfynol®465 micelles (microemulsion). Solution properties were not significantly altered after addition of microemulsion regardless of surfactant and/or eugenol concentration. Transmission electron imaging revealed a homogeneous distribution of microemulsion throughout the nanofibers. Release studies suggested a burst release mechanism of encapsulated eugenol microemulsion, potentially due to hydrophilicity of the polymeric carrier, while faster release was observed in samples with a higher eugenol loading ratio in the microemulsion. Antimicrobial activity of produced nanofibers carrying phytophenol microemulsions was evaluated against two strains of Salmonella Typhimurium and Listeria monocytogenes. Overall, the functionalized nanofibers had higher antimicrobial efficacies against Gram-negative than Gram-positive bacterial strains and were also more effective than pure eugenol microemulsion added at respective concentrations to the test system possibly due to a faster exhaustion and loss of antimicrobial activity in free microemulsions. Results of this study suggest that composite solutions of biopolymers, synthetic polymers, and micellar surfactant solutions can be successfully electrospun potentially offering a new means to functionalize biopolymeric nanofibers.

The hypocholesterolemic effect of certain polysaccharides has been attributed to their ability to bind bile acids. The purpose of this study was to better understand bile acid - polysaccharide interactions by systematically characterizing the interactions between selected polysaccharides (chitosan and pectin) and anionic surfactants (sodium dodecyl sulfate (SDS) and sodium taurocholic acid (NaTCA)) using isothermal titration calorimetry (ITC), surfactant selective electrode (SSE) and turbidity measurements. Initially, the influence of environmental conditions (pH, ionic strength and temperature) on the properties of SDS and NaTCA in buffer solutions was characterized. The CMC's (critical micelle concentrations) were largely independent of temperature and pH, but decreased appreciably as the ionic strength increased. In general, the micellization behavior of NaTCA was different from that of SDS because of their different molecular structures. The influence of environmental conditions on the interactions between SDS and NaTCA with pectin and chitosan were then studied. SDS bound strongly to chitosan and formed insoluble complexes, which was attributed to electrostatic attraction. For SDS-chitosan interactions, temperature did not have a large affect on T1 (onset binding), T2 (surfactant concentration at polymer saturation) or CMC* (effective CMC in the presence of polymer). Strong binding only occurred at pH values where the chitosan was cationic (pH 3 and 5), but not when it was uncharged (pH 7). Salt (0 to 200 mM) decreased the CMC* because of the depression of the CMC of free SDS in solution. SDS bound weakly to pectin and formed soluble complexes, which was attributed to hydrophobic interactions. The general characteristics of NaTCA-chitosan interactions were fairly similar to those of SDS-chitosan interactions. The binding interaction was exothermic at all temperatures studied (10 to 50°C), suggesting that it was electrostatic in origin. The T1, T2 and CMC* values were influenced by salt and pH as described for SDS. In addition, only a weak binding interaction was observed between pectin and NaTCA. This study provides information that may lead to the rational design of polysaccharide-based food ingredients with beneficial nutritional and functional characteristics.

Chronic oxidation linked diseases are on a rise and are one of the leading causes of death globally. Epidemiological evidence increasingly points towards consumption of fruits and vegetables as a preventive way to manage early stages of chronic oxidation linked diseases. Oxidation linked diseases are caused by excessive reactive oxygen species (ROS) generated by a disruption in cellular antioxidant homeostasis due to an overload of calories combined with stress, no excerise and a diet low in antioxidants. Phenolic compounds can not only act as antioxidants but also stimulate the activities of antioxidants enzyme through protective pathways which can help modulate cellular protection. The aim of this dissertation was to use probiotic fermentation to enhance the phenolic and antioxidant compounds in fruit systems which can form the basis of functional food design. The potential of these food systems for disease prevention was investigated in eukaryotic systems through understanding the role of critical metabolic pathways involed in prevention of oxidation linked chronic diseases. Based on structure-function rationale, antioxidant, anti-hyperglycemia and anti-hypertensive potential of phenolic compounds in tea and the effect of extraction time and different degrees of fermentation were investigated in in vitro models. Results indicated that the most fermented teas and a longer extraction time had the highest potential. Further these extracts also had higher H. pylori inhibition potential. Probiotic fermentation of fruit juices with L. helveticus was used to mobilize phenolics and improve biological functionality by maintaining a consistent phytochemical profile. Results indicated that total phenolic and antioxidant potential decreased with feremnetation. However &agr;-glucosidase inhibitory activity and H. pylori inhibitory potential increased with fermentation. Investigation into the mechanism of H. pylori inhibition with fermented cherry extracts revealed inhibition of proline dehydrogenase as the likely mode of action. The potential of fermented apple extracts was further investigated as a phytochemical elicitor in eliciting phenolic and antioxidant response in germinating fava bean. The results indicated a stimulation of phenolic and antioxidant response likely through the stimulation of carbon flux through glycolytic pathways. In yeast, fermented apple extracts accelerated cell death in the presence of peroxide stress in pretreatment model whereas it provided protection against oxidative stress and prevented cell death in concurrent model. Chitosan oligosachharide treatment was investigated as a potential replacement of cancer causing diphenylamine treatment for scald reduction in Cortland apples. Although the treatment did not have any effect on scald reduction, it provides better protection in storage by stimulating phenolic and antioxidant response which related to better health relevant functionality.

There is growing interest in the use of nanoemulsions as delivery systems for lipophilic functional agents in food and beverage products due to their high optical clarity, physical stability and bioavailability. The goal of this research is to establish quantitative structure-function relationships to allow rational formulation of food-grade nanoemulsions for food and beverage applications. Initially, formation of oil-in-water nanoemulsions using a low energy method was examined. Nanoemulsions were formed using the phase inversion temperature (PIT) method, which involves heating a surfactant, oil, water (SOW) systems near the PIT, and then cooling rapidly with stirring. Preliminary experiments were carried out using a model system consisting of a non-ionic surfactant (C12E4), hydrocarbon oil (tetradecane), and water. Nanoemulsions were formed by holding SOW mixtures near their PIT (38.5 °C) and then cooling them rapidly to 10 °C. The PIT was measured using electrical, conductivity and turbidity methods. The optimum storage temperature for PIT-nanoemulsions was about 27 °C lower than the PIT. The stability of PIT-nanoemulsions at ambient temperatures can be improved by adding either Tween 80 (0.2 wt%) or SDS (0.1 wt%) to displace the C12E4 (Brij 30) from the nano-droplet surfaces. Experiments were then carried out to establish if stable nanoemulsions could be formed using the PIT method from food-grade ingredients. Nanoemulsions were fabricated from a non-ionic surfactant (Tween 80) and flavor oil (lemon oil) by heat treatment. Different types of colloidal dispersion could be formed by simple heat treatment (90 °C, 30 minutes) depending on the surfactant-to-oil ratio (SOR): emulsions at SOR < 1; nanoemulsions at 1 < SOR < 2; microemulsions at SOR > 2. The results suggested that there was a kinetic energy barrier in the SOW system at ambient temperature that prevented it from moving from a highly unstable system into a nanoemulsion system. The conditions where stable nanoemulsions could be fabricated were also established when sucrose monopalmitate (SMP) and lemon oil were used as the surfactant and oil phase. Nanoemulsions (r < 100 nm) were formed at low surfactant-to-oil ratios (SOR < 1) depending on homogenization conditions, whereas microemulsions (r < 10 nm) were formed at higher ratios (SOR > 1). Relatively stable nanoemulsions could be formed at pH 6 and 7, but extensive particle growth/aggregation occurred at lower and higher pH values. Flavor oil nanoemulsions were also formed using an emulsion titration method that involves titration of emulsion droplets into surfactant micelle solutions. In this study, the effectiveness of nanoemulsion formation using nonionic surfactants (sucrose monopalmitate (SMP) and/or Tween 80 (T80) was investigated. Lemon oil was transferred from emulsion droplets into the micelle phase until a critical lemon oil concentration (Csat ) was reached. The solubilization process was rapid (< few minutes), with the rate increasing with increasing surfactant concentration. The value of Csat increased with increasing surfactant concentration and was higher for SMP than Tween 80. The influence of lemon oil composition (1×, 3×, 5×, and 10×) on the formation and properties of oil-in-water nanoemulsions was also studied. Initially, the composition, molecular characteristics, and physicochemical properties of four lemon oils were established. The main constituents in 1-fold lemon oil were monoterpenes (> 90 %), whereas the major constituents in 10-fold lemon oil were monoterpenes (≈ 35%), sesquiterpenes (≈ 14%) and oxygenates (≈ 33%). The density, interfacial tension, viscosity, and refractive index of the lemon oils increased as the oil fold increased ( i.e., 1× < 3× < 5× < 10×). The stability of oil-in-water nanoemulsions produced by high pressure homogenization was strongly influenced by lemon oil composition. The lower fold oils were highly unstable to droplet growth during storage (1×, 3×, 5×) with the growth rate increasing with increasing storage temperature and decreasing oil fold. Oil fold also affected the solubilization and stability of lemon oil nanoemulsions titrated into a non-ionic surfactant (Tween 80) solution. The movement of oil molecules from nanoemulsion droplets to surfactant micelles increased with increasing lemon oil fold. Finally, nanoemulsions were used as delivery systems for β-carotene, a bioactive lipophilic component. The influence of carrier oil composition (ratio of digestible to indigestible oil) on the physical stability, microstructure, and bioaccessibility of β-carotene nanoemulsions was investigated using a simulated gastrointestinal tract model. The extent of free fatty acid production in the small intestine increased as the amount of digestible oil in the droplets increased. The bioaccessibility of β-carotene also increased with increasing digestible oil content, ranging from ≈ 5% for the pure lemon oil system to ≈ 76% for the pure corn oil system.

This body of work investigates various techniques for the surface modification of food contact materials for use in food packaging and processing applications. Nanoscale changes to the surface of polymeric food packaging materials enables changes in adhesion, wettability, printability, chemical functionality, and bioactivity, while maintaining desirable bulk properties. Polymer surface modification is used in applications such as antimicrobial or non-fouling materials, biosensors, and active packaging. Non-migratory active packagings, in which bioactive components are tethered to the package, offer the potential to reduce the need for additives in food products while maintaining safety and quality. A challenge in developing non-migratory active packaging materials is the loss of biomolecular activity that can occur when biomolecules are immobilized. Polyethylene glycol (PEG), a biocompatible polymer, is grafted from the surface of ozone treated low-density polyethylene (LDPE) resulting in a surface functionalized polyethylene to which a range of amine-terminated bioactive molecules can be immobilized. The grafting of PEG onto the surface of polymer packaging films is accomplished by free radical graft polymerization, and to covalently link an amine-terminated molecule to the PEG tether, demonstrating that amine-terminated bioactive compounds (such as peptides, enzymes, and some antimicrobials) can be immobilized onto PEG-grafted LDPE in the development of non-migratory active packaging. Fouling on food contact surfaces during food processing has a significant impact on operating efficiency and can promote biofilm development. Processing raw milk on plate heat exchangers results in significant fouling of proteins as well as minerals, and is exacerbated by the wall heating effect. An electroless nickel coating is co-deposited with polytetrafluoroethylene onto stainless steel to test its ability to resist fouling on a pilot plant scale plate heat exchanger. Further work was performed to test the stability of non-fouling material after extended exposure to an alkali detergent or acid sanitizer formulated for clean-in-place procedures in dairy processing facilities. Additionally, the anti-corrosive property of the surface coating was tested on carbon steel against chlorine ions, a common corrosive agent found in the food industry. Accelerated corrosion and long-term chemical exposure studies were conducted to measure the coating stability against the harsh corrosive agents.