Small amounts of polymers are typically used in flavor and food applications. Polymers are typically applied in thin coatings which allow for a cost-effective encapsulation with desirable barrier properties. Understanding the properties of thin barrier coatings is essential to obtaining optimal encapsulation performance. Many of the polymers used in the flavor and food industry are cross-linked hydrogels, which are water insoluble but water swellable. Hydrogel barriers allow water soluble components to be extracted from the encapsulation system. Flavor components having a large affinity for water will be extracted from the encapsulation system while more hydrophobic flavor components will remain encapsulated. Preferential flavor extraction is a large problem for the flavor industry because flavors are complicated mixtures of both hydrophilic and hydrophobic components.

Understanding diffusion and permeability coefficients is desirable for creating optimized encapsulation systems. However, creating thin uniform films reproducibly can be challenging and expensive. In the past, thick polymer films were cast onto a metal sheet and cross-linked with the appropriate chemicals. The method produced wrinkled and inconsistent film thicknesses. The inconsistent films produced irreproducible diffusion and permeability coefficient data. New testing methods were developed to understand flavor partitioning across thin hydrogel membranes. One focus of the present work was to create 10µm to 50µm polymer films reproducibly with uniform thicknesses. The second focus of this project was to determine thin film diffusion and permeability coefficients of the created polymer films. The first portion of this thesis discusses the creation of thin polymer films. Calcium alginate and calcium pectinate films were created using a lightly scuffed metal sheet. The sheet was then used in a leveling apparatus which provided a level surface for film casting. The polymer films were characterized by micrometer measurement, environmental scanning electron microscopy (ESEM) and swelling ratio experiments. Micrometer measurements demonstrated the successful preparation of 21 to 23 (+/- 1) µm calcium alginate films and 19 to 20 (+/- 1) µm calcium pectinate films. The 4 to 6% relative standard deviation was considered acceptable for the present work. The calcium alginate and calcium pectinate films were also analyzed by ESEM. Both sides of the films were analyzed at 200X and 1500X magnifications. The polymer film surface exposed to the scuffed metal sheet produced a rough and irregular surface. The polymer film surface not exposed to the scuffed metal sheet had a smooth and uniform surface. Film thickness measurements were also performed using the ESEM computer software to further verify the film thickness measurements obtained from the micrometer. The ESEM film thickness measurements demonstrated a 20.9 (+/- 1.1) µm calcium alginate film and a 20.2 (+/- 0.7) µm calcium pectinate film had been produced. Both films demonstrated an average relative standard deviation of 4 to 6% which was considered acceptable for the present work. The ESEM measurements of film thickness demonstrate the methodology for creating thin polymer films is reproducible and within the desired thickness range. However, the scuffed metal sheet creates films that are rough on one side and smooth on the other side. Preliminary polymer swelling ratio experiments in distilled water showed calcium alginate films swell to 2.4 times their original dry weight and calcium pectinate films swell by a factor of 3.8. The large swelling ratios for the films indicated that distilled water was an appropriate solvent for determining film permeability and diffusion coefficients.

The second portion of this thesis focused on determining film diffusion and permeability coefficients. A new thin-film diffusion cell (TFD) was built and coupled to a UV/VIS spectrophotometer fitted with a fiber optic probe which allowed for in-situ measurement of analytes which absorb ultraviolet radiation such as benzaldehyde. Permeability measurements using benzaldehyde demonstrated a permeability coefficient of 3 X 10^-5 cm/sec. (+/- 5%) for the 22 (+/- 1) µm calcium alginate film and 2 X 10^-4 cm/sec. (+/-6%) for the 20 (+/- 1) µm calcium pectinate film. Diffusion coefficients were then calculated for the two films. The diffusion coefficient for a 22 (+/-1) µm calcium alginate film was 6.5 X 10 ^-8 (+/- 11%) cm²/sec while the diffusion coefficient for a 20 (+/-1) µm calcium pectinate film was 3.9 X 10^-7 (+/- 12%) cm²/sec. The relative standard deviations for the permeability and diffusion coefficients were considered acceptable for this study. The permeability and diffusion coefficients indicated a calcium pectinate film is more permeable than a calcium alginate film of equal thickness.