No description available.

No description available.

No description available.

No description available.

Properties of plasticized thermoplastic com and pulse starches and their blends with poly (lactic acid) (PLA) were studied. Water and glycerol acted as plasticizer components for a ratio of starch/glycerol/water (wt/wt) fixed at 50/36/14 based on previous studies. PLA was used in blends to improve the properties of thermoplastic starch (TPS). Maleic anhydride (MA) was used as a coupling agent to increase the miscibility of PLA and TPS phases. Cloisite 30B, a type of organoclay, was added into the material system to improve the properties of blends. In order to enhance the hydrophobicity, alkyl ketene dimmer (AKD), used as a sizing agent, were introduced to material system. Both internal and surface sizing methods were applied. Measurements of rheological and mechanical properties were performed on a Rosand capillary rheometer and Instron tensile testing machine. The thermal and morphological properties of blends were characterized using differential scanning calorimetry and scanning electron microscopy. The contact angles were measured using a goniometer equipped with a video camera and a computer with drop shape analysis software for calculating the contact angles. The use of maleic anhydride as a coupling agent significantly improved the tensile strength and modulus of blends and the blend morphologies were more homogeneous. Improvements in tensile strength and modulus were achieved as Cloisite 30B nanoclay was used as a filler in TPS/PLAgMA blends. Some hydrophobicity was obtained for blends with Cloisite 30B. Blends ofTPS/PLAgMA/clay showed shear-thinning behaviors at 150°C . . / Thesis / Master of Applied Science (MASc)

No description available.

Ready-to-eat meat products have been implicated in several foodborne listeriosis outbreaks. Microbial contamination of these products can occur after the product has been thermally processed and is being rapidly chilled using salt brines. The objective of this study was to determine the effect of ultraviolet irradiation on the inactivation of Listeria monocytogenes and lactic acid bacteria in a model brine chiller system. Two concentrations of brines (7.9%w/w or 13.2%w/w) were inoculated with a ~6.0 log10 CFU/ml cocktail of L. monocytogenes or lactic acid bacteria and passed through the ultraviolet (UV) treatment system for 60 minutes. Three replications of each bacteria and brine combination were performed and resulted in at least a 4.5 log reduction in microbial numbers in all treated brines after exposure to ultraviolet light. Bacterial populations were significantly reduced after five minutes exposure to UV light in the model brine chiller as compared to the control, which received no UV light exposure (P<0.05). The maximum rate of inactivation for both microorganisms in treated brines occurred between minute 1 and 15 of ultraviolet exposure. Overall, results indicate that inline treatment of chill brines with ultraviolet light (UVC) shows promise in inactivating L. monocytogenes and lactic acid bacteria. Due to the low capital involved in initiating a continuous inline UV system, the use of ultraviolet energy may prove to be beneficial for effectively controlling pathogens in recycled chill brines without interrupting the chilling operation. An inline ultraviolet system could be used in a hazard analysis and critical control points plan. / Master of Science

Listeria monocytogenes is the major pathogen in ready-to-eat meat products such as deli meats and frankfurters. Contamination can occur via the salt brines that are used to cool thermally processed meats. Both L. monocytogenes and lactic acid bacteria can grow and thrive under these brine conditions, and may become competitive with each other for available nutrients. The objective of this study was to determine the effect of a three strain cocktail of lactic acid bacteria Enterococcus faecalis, Carnobacterium gallinarum, and Lactobacillus plantarum on the survival of Listeria monocytogenes and Listeria innocua in brines stored under low temperatures up to 10 days. Three brine concentrations (0%, 7.9%, and 13.2% NaCl) were inoculated with ~7.0 log₁₀ cfu/ml of one of five cocktails (L. monocytogenes, L. innocua, lactic acid bacteria (LAB), L. monocytogenes + LAB, or L. innocua + LAB) and stored for 10 days at either 4°C or 12°C. Three replications of each brine/cocktail/temperature combination were performed. No reductions of L. monocytogenes were seen in 7.9 or 13.2% NaCl with LAB; however, reductions of L. monocytogenes were seen in the 0% NaCl with LAB (1.43 log at 4°C and 3.02 log at 12°C). Listeria innocua was significantly less resilient to environmental stresses than L. monocytogenes, both with and without LAB present (p<0.05). This research indicates these strains of lactic acid bacteria are not effective at reducing L. monocytogenes in brines at low temperatures. Furthermore, the use of L. innocua as a model for L. monocytogenes is not appropriate under these environmental conditions. / Master of Science

No / In this work, energy consumption in a middle vessel batch reactive distillation (MVBRD) column is considered for the production of lactic acid via hydrolysis of methyl lactate. A dynamic optimization problem incorporating a process model is formulated to minimize the batch time which consequently minimizes the total energy consumption. The problem is subject to constraints on the amount and purity of lactic acid. The optimisation variables are reflux ratio and/or reboil ratio which are treated as piecewise constant. The earlier work of the authors on energy consumption in conventional batch reactive distillation column (CBRD) for the same reaction system is used for comparative analysis with the energy consumption in MVBRD. As an example, for a given separation task, the optimization results show that MVBRD is capable of saving over 23 % energy compared to energy consumption in CBRD column for the same task.

The context of this thesis is a research project focused on the investigation of a renewable biopolymer-poly(lactic acid) (PLA) as a potential replacement of petroleum-based polymers in advanced nanocomposites reinforced with Microfibrillated cellulose (MFC). MFC is extracted from wood, which is a renewable, sustainable, carbon neutral and recyclable material. This advanced MFC-PLA bio- based composite material is expected to allow for the substitution of petroleum-based plastics in various markets and applications. The specific objectives of the thesis are: 1) to describe the morphological characterization of MFC used for prototype MFC-PLA composites, and 2) to determine the mechanical properties of the prototype MFC-PLA nanocomposites formulation generated in form of thin transparent films. In order to meet this objective it was necessary to: 2.1) develop a methodology for optical strain measurement in transparent thin films; and 2.2) develop an effective methodology for obtaining multiple mechanical properties from small number of specimens of prototype materials subjected to tensile tests. Two types of MFC, one obtained by courtesy of University of Maine and the other purchased from Innventia AB company, were investigated under a field emission scanning electron microscopy (FESEM). The micrographs obtained from FESEM showed that both types of MFC were of complex hierarchical structures, which did not allow qualitative characterization of the morphological features in terms of particulate composites nor cellular solids. Since prototype formulations of MFC-PLA composites were generated in small amounts (typically one Petri dish) in a form of thin transparent films, there was a need for quick and efficient assessment of their key mechanical properties that would provide feedback and guide further prototyping work. An optical measurement method based on digital image correlation (DIC) principle was developed to measure the deformation and strains of the tensile film samples. In our study, the accuracy and precision of the measurement of deformation were ±1.5 µm and 0.4 µm respectively. The corresponding accuracy and precision in terms of strains were ±30 µstrain and 75 µstrain respectively. This method can be successfully used to determine the critical mechanical properties, such as elastic modulus, toughness and Poisson's ratio, of transparent thin films by a single tensile test, all of which require precise strain measurement. In addition, this optical measurement method makes it possible to significantly simplify the testing for measuring essential work of fracture (EWF), an important material property of thin transparent films. In traditional method, measurement of EWF requires large amount of notched specimens. However, our study showed that only a small amount of notched specimens were needed to measure the EWF of a material. This method could not be successfully used to determine EWF from un-notched tensile specimens. / Graduation date: 2012 / Folder labeled "UMaine MFC aerogel" contains SEM micrographs of MFC from University of Maine (referred as type A MFC in the thesis). Two pieces of leaf-like flakes at different locations were cut by Focused Ion Beam (FIB) in order to observe the internal structure of the flakes. Folder "FIB_01 ": a series of SEM micrographs of FIB-cut flake at different magnification levels. Folder "FIB_02 ": another series of SEM micrographs of FIB-cut flake at various magnification levels. Folder labeled "Swedish MFC aerogel" contains SEM micrographs of MFC from Innventia AB company, Sweden (referred as type B MFC in the thesis). There is a series of SEM micrographs of type B MFC aerogel at various magnification levels in this folder.