Phương pháp tạo màng calcium alginate and calcium pectinate films

UNIVERSITY OF CINCINNATI Date: 10/24/2007_______________ , RobertB. WielanO ^5____________________________________________________5 hereby submit this work as part of the requirements for the degree of: Master of Science in: Chemistry It is entitled: Preparation of Calcium Alginate and Calcium Pectinate Films and Determinations of Their Permeabilities This work and its defense approved by: Chair: 47. JamcsO.OlcrC Di.O/tolO/raiio Or. Cci/CcliiCar Preparation of Calcium Alginate and Calcium Pectinate Films and Determinations of Their Permeabilities A dissertation to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in the Department of Chemistry by Robert B. Wieland Bachelors of Science in Chemical Technology University of Cincinnati, June 2001 Committee Chair: Dr. James E. Mar kABSTRACT 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 10^m to 50^m 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. Calciumalginate 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) calcium alginate films and 19 to 20 (+/- 1) 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) calcium alginate film and a 20.2 (+/- 0.7) 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. 5 5 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 3X 10-5 cm/sec. (+/- 5%) for the 22 (+/- 1) calcium alginate film and 2 X 10-4 cm/sec. (+/-6%) for the 20 (+/- 1) calcium pectinate film. Diffusion coefficients were then calculated for the two films. The diffusion coefficient for a 22 (+/-1) calcium alginate film was 6.5 X 10-8 (+/- 11%) cm2/sec while the diffusion coefficient for a 20 (+/-1) 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.ACKNOWLEDGEMENTS I would like to express my gratitude to Dr. Dave Siegel for the guidance and support shown to me while obtaining a graduate degree. I acknowledge my graduate achievement would not have been possible without the patience, flexibility and understanding shown by this man. I would also like to thank Dr. Robert Eilerman for his flexibility allowing me to achieve an academic milestone while maintaining full time duties at the Givaudan Flavor Corporation. I would like to acknowledge the financial support of the Givaudan Flavor Corporation. The financial support allowed for critical glassware to be purchased and allowed me to obtain a graduate degree. I would like to give a heartfelt thank you to Dr. Jing Zhang for helping me understand diffusion and permeability. In this way, Dr. Zhang helped me become a better chemist with an increased knowledge of polymer 6 6 systems. I appreciate the guidance Dr. James Mark has given while writing my graduate thesis and during my academic career. His insight has been valuable and informative. I would like to thank my mother Brenda Wilson for her endless encouragement. Your determination, work ethic and loving support has enabled me to be successful in the workplace and in academia. I am grateful for the support and encouragement shown by my wife Jessica Wieland. Without her support this achievement would not be possible. Thank you for understanding the extra hours at school and the extra hours of homework which kept us apart. I could not ask for a more supportive and inspiring wife. TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES 7 7 Table 9: Benzaldehyde absorbance measurements across calcium alginate films 34 Table 10: Benzaldehyde absorbance measurements across calcium alginate films.3 8 8 9. INTRODUCTION 4Both flavors and active ingredients such as vitamins impart important characteristics to products desirable to consumers in the marketplace. However, flavors and active ingredients can be lost or degraded during food processing, with the result of losing consumer benefit. However, critical components can be encapsulated using polymeric materials to prevent such losses. Polymers are typically applied in thin coatings which allows for a cost effective encapsulation with functional properties 1 . Understanding the properties of thin barrier coatings is essential to obtain optimal encapsulation performance. The food and flavor industry have used polymeric materials for decades as bulking agents, viscosifiers, and barrier materials for various encapsulation systems. Materials such as sugar, maltodextrin, pectin and alginate can be used to create water soluble encapsulation systems 2 . Pectin and alginate materials are of great interest to the flavor industry due to the cross-linkable nature of these natural polymer materials 3 . Cross-linked pectin and alginate form hydrogel barriers which are water insoluble but water swellable 4 . The swelling properties of hydrogel barriers can be manipulated by varying levels of chemical cross-linking along these carbohydrate chains 5 . Highly cross-linked polymer materials typically demonstrate minimized diffusion properties which creates an effective barrier reducing flavor loss during cooking processes. Lightly cross-linked polymers become less effective barriers due to increased diffusion properties. Flavor encapsulation systems containing hydrogels have been utilized in food to create products with increased flavor perception6,7. However, flavors encapsulated in hydrogel systems typically need to be reformulated to preserve such a desirable perception. The swelling property of hydrogel barriers allows flavor components having a large affinity for water to be extracted from the encapsulation system while more hydrophobic flavor components remain encapsulated. The swelling property of hydrogel barriers is a large problem for the flavor industry because flavors are complicated 1 Gutcho, M.H. Microcapsules and Other Capsules. Noyes Data Corporation: Park Ridge, NJ, 1979. 2 Risch, S.J. (1995). Encapsulation: Overview of Uses and Techniques. In Risch, S.J. and Reineccius, G.A. (Ed.) Encapsulation and Controlled Release of Food Ingredients (pp 2-7). Washington, DC: American Chemical Society. 3 Schlemmor, U. (1989) Studies of the binding of copper, zinc and calcium to pectin, alginate, carrageenan and gum guar in HCO"3 - CO2 buffer. Food Chemistry, 32 (3), pg 223-234. 4 Bajpai, S.K.; Sharma, S. (2004) Investigation of swelling/degradation behavior of alginate beads crosslinked with Ca2+ and Ba + ions. Reactive & Functional Polymers, 59 (2004), pg 129-140. 5 Flory, P.J. Principles of Polymer Chemistry. Cornell University Press: Ithaca, NY, 1953. i 10. INTRODUCTION mixtures of both hydrophilic and hydrophobic components. For example, typical fruit flavors contain numerous individual ingredients which impart a delicate balance and flavor profile. Individual cherry flavor ingredients have vegetable oil:water partition coefficients ranging from 4 to 1. A partition coefficient, denoted as P in this document, is the concentration ratio of a compound in two immiscible solvents at equilibrium8,9. The P coefficient in this study is a measure of differential compound solubility between vegetable oil and water. The higher the P value the more hydrophobic the compound. Since most food applications are exposed to water over time, maintaining a balanced flavor profile is difficult. Creatin i [...]... thickness of the calcium alginate and calcium pectinate films The films were cut into 5cm X 5cm squares and ten micrometer measurements were performed and recorded An average micron thickness, standard deviation and relative standard deviation was then determined for each polymer film 2.5.2 Environmental Scanning Electron Microscopy (ESEM) Calcium alginate and calcium pectinate films were sampled and sent... circumstances: thin films become very brittle, brittle and cracked films lead to ineffective barriers, and thin films are hard to cast uniformly The thin films created were uniform and reproducible which ensured a robust method and reliable data For the present work, two calcium cross-linkable polymers were chosen for study Alginate and pectin were chosen for their acceptance in the food and flavor industry... polymer film and aqueous phase (Kd = 1 is assumed for this analysis) 3 Results and Discussion 3.1 Micrometer Measurements Ten individual calcium alginate films had been created using the prepared thin film sheet and leveling apparatus The measurements obtained using the micrometer demonstrated 21 to 23 (+/- 1) calcium alginate films had been produced The thickness measurements for calcium alginate films are... containing the alginate and treated with calcium chloride to form a water insoluble precipitate The calcium alginate is then recovered, pressed to remove excess water and treated with a hydrochloric acid solution The acid-washed alginate cake is then pressed and washed with a basic solution to produce sodium alginate which is water soluble The solubilized alginate is then spray dried and sieved to the... shown Table 2 The same methodology mentioned previously was applied to the calcium pectinate films The measurements obtained using the micrometer demonstrated 19 to 20 (+/- 1) calcium pectinate films had been produced The thickness measurements for calcium pectinate films are shown in Table 3 Both films demonstrated a relative standard deviation of 4 to 6% which was considered acceptable for the presented... Creating Calcium Alginate Films Approximately 250.0g of the 1.0% sodium alginate solution was poured into a lightly scuffed cookie sheet and allowed to stand in a fume hood for 24 hours on a leveling apparatus The 1% sodium alginate solution delivered 2.5g of sodium alginate across 1205 cm2 of surface area on the cookie sheet As the water evaporated from the sodium alginate solution a thin film of sodium alginate. .. high-M alginates These alginates produce gels that are elastic, and this increases freeze-thaw stability The block sequences of glucuronic acid and mannuronic acid monomer units also affect alginate functionality Varying block lengths such as GG, MG and MM produce gels with blended properties and regimes Milanovanovic, A.; Bozic, N and Vujcic Z (2007) Cell wall invertase immobilization within calcium alginate. .. drugs and cellular materials13 Alginate has also been used to dehydrate products such as paper and textiles, as flame retardants for fabrics, and as blood detoxifiers 1.4 Alginate: Structure Alginate is a complex carbohydrate comprised of glucuronic and mannuronic acid monomers Based on the seaweed source and processing, alginate can be produced with varying glucuronic and mannuronic acid contents 14... and allowed to stand for 30 minutes The 2% calcium chloride solution delivered 5g of calcium chloride to 2.5g of sodium alginate The calcium displaced the sodium in the alginate film forming a cross-linked water insoluble calcium alginate film The calcium chloride solution was then decanted from the cookie sheet The cookie sheet containing the cross-linked alginate film was rinsed three times with 250.0g... placed in a fume hood and allowed to stand for 24 hours The film slowly peeled off the cookie sheet Thin uniform calcium pectinate films were created containing no wrinkles or high spots The film was cut into 5 cm X 5 cm squares and stored in a sealed container The dried calcium pectinate film demonstrated a moisture content of 2.1 to 2.5% Figure 2.4.4-1: 20pm calcium pectinate film 2.4.5 Creating 1000ppm