Phương pháp tạo màng calcium alginate and calcium pectinate

The second focus of this project was to determine thin film diffusion and permeability coefficients of the created polymer films.. The ESEM film thickness measurements demonstrated a 20.

UNIVERSITY OF CINCINNATI

Date: _

I, _, hereby submit this work as part of the requirements for the degree of:

_ _

10/24/2007 Robert B Wieland

Master of Science

Chemistry

Preparation of Calcium Alginate and Calcium Pectinate Films

and Determinations of Their Permeabilities

Dr James E Mark

Dr Estel Sprague

Dr Carl Seliskar

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

ABSTRACT

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 3X 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

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 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

ABSTRACT……….… ii

ACKNOWLEDGEMENTS……….… v

TABLE OF CONTENTS……….…vi

LIST OF FIGURES……….……… ……… … viii

LIST OF TABLES……… ……… ……….………… xi

1 INTRODUCTION………1

1.1: Pectin: Sourcing, Manufacture and Functionality……… 5

1.2: Pectin: Structure……….7

1.3: Alginate: Sourcing, Manufacture and Functionality……… 8

1.4: Alginate: Structure……….………… ………10

2 EXPERIMENTAL SECTION……… 12

2.1: Experimental Objectives……….12

2.2: Raw Materials……… ……….13

2.3: Procedures……… ……….14

2.3.1: Film Sheet Preparation……… …….14

2.3.2: Leveling Film Sheet Apparatus……… 15

2.4: Procedures-Sample Preparation……… 16

2.4.1: Creating 1.0% Sodium Alginate Solutions………16

2.4.2: Creating Calcium Alginate Films………17

2.4.3: Creating 1.0% Pectin Solutions 18

2.4.4: Creating Calcium Pectinate Films……… 18

2.4.5: Creating 1000PPM Benzaldehyde Standards in Miglyol 812………20

2.4.6: Creating Benzaldehyde Standards in Distilled Water……….……20

2.5: Characterization Techniques……….21

2.5.1: Micrometer Measurements……… 21

2.5.2: Environmental Scanning Electron Microscopy (ESEM)….….….…….…….22

2.5.3: Swelling Ratio Measurement (SR) 22

2.5.4: Polymer Film Diffusion Analysis……….………23

2.5.4.1: UV/VIS Absorbance Linear Regression Calibration….….……….….23

2.5.4.2: UV/VIS Thin Film Diffusion Analysis (TFD)……… 24

3 RESULTS and DISCUSSION………27

3.1: Micrometer Measurements……… 27

3.2: Environmental Scanning Electron Microscopy (ESEM)……….….….……….28

3.3: Swelling Ratio Measurement (SR) 31

3.4: Polymer Film Diffusion Analysis………….……… ………33

3.4.1: UV/VIS Absorbance Linear Regression Calibration….….……….33

3.4.2: UV/VIS Thin Film Diffusion Analysis (TFD)……….….………… …….35

4 CONCLUSIONS……… ……….38

LIST OF FIGURES

Figure 1.2-1: Structure of the pectin molecule………7

Figure 1.2-2: Structure of the calcium pectinate molecule……….……… 8

Figure 1.4-1: Alginate monomers……… ……… 10

Figure 1.4-2: Alginate block types……… 11

Figure 1.4-3: Calcium binding site in polyguluronate dimer… ……… 12

Figure 1.4-4: Calcium alginate cross-linked “Egg box” model……… 12

Figure 2.2-1: Structure of benzaldehyde… ……….……… 14

Figure 2.3.1-1: Scuffed cookie sheet……… 15

Figure 2.3.2-1: Leveling film apparatus with key measurements………….………… 16

Figure 2.3.2-2: Leveling film apparatus containing film sheets……… 16

Figure 2.4.2-1: 20μm calcium alginate film……… ….…18

Figure 2.4.4-1: 20μm calcium pectinate film……….…19

Figure 2.5.4.1-1: UV/VIS spectrophotometer……… ……… 23

Figure 2.5.4.1-2: Fiber optic probe fitted with UV/VIS spectrophotometer…… … 24

Figure 2.5.4.2-1: Schematic of thin film diffusion (TFD) apparatus…….……… 25

Figure 3.2-1: ESEM analysis of calcium alginate and pectinate rough film side…… 29

Figure 3.2-2: ESEM analysis of calcium alginate and pectinate smooth film side … 30 Figure 3.4.1-1: Linear regression chart for benzaldehyde standards……….……… 35

Figure 3.4.2-1: Permeability coefficient for calcium alginate film…….……….……… 37

Figure 3.4.2-2: Permeability coefficient for calcium alginate film……… …37

LIST OF TABLES

Table 1: Benzaldehyde standard dilutions……….21

Table 2: Micrometer measurements for thin calcium alginate films……… 28

Table 3: Micrometer measurements for thin calcium pectinate films……… ……… 28

Table 4: Calcium alginate film thickness measurements by ESEM analysis……… 31

Table 5: Calcium pectinate film thickness measurements by ESEM analysis … 31

Table 6: Swelling ratio measurements of calcium alginate thin films……….… 33

Table 7: Swelling ratio measurements of calcium pectinate thin films ……… 33

Table 8: Average absorbance values of benzaldehyde standards………… 34

Table 9: Benzaldehyde absorbance measurements across calcium alginate films 34 Table 10: Benzaldehyde absorbance measurements across calcium alginate films.34

1 INTRODUCTION

Both 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 properties1 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 systems2 Pectin and alginate materials are of great interest to the flavor industry due to the cross-linkable nature of these natural polymer materials3 Cross-linked pectin and alginate form hydrogel barriers which are water insoluble but water swellable4 The swelling properties of hydrogel barriers can be manipulated by varying levels of chemical cross-linking along these carbohydrate chains5 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       

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 – CO 2 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 Ba2+ ions Reactive & Functional Polymers, 59 (2004), pg 129-140

5 Flory, P.J Principles of Polymer Chemistry Cornell University Press: Ithaca, NY, 1953

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 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 Creating

      

6 Soper, J.C (1995) Utilization of Coacervated Flavors In Risch, S.J and Reineccius, G.A (Ed.)

Encapsulation and Controlled Release of Food Ingredients (pp 104-112) Washington, DC: American Chemical Society

7 King, A.H (1995) Encapsulation of Food Ingredients: A Review of Available Technology, Focusing

on Hydrocolloids In Risch, S.J and Reineccius, G.A (Ed.) Encapsulation and Controlled Release of Food Ingredients (pp 26-37) Washington, DC: American Chemical Society

8   Seuvre, A.; Philippe, E.; Rochard, S and Voilley, A (2006) Retention of aroma compounds in food

matrices of similar rheological behavior and different compositions Food Chemistry, 96 (1), pg

104-114

9 Roberts, D.D (1998) Relationship Between Aroma Compounds’ Partitioning Constants and Release

During Microwave Heating In Mussinan, C.J and Morello, M.J (Ed.) Flavor Analysis Developments in Isolation and Characterization (pp 61-68) Washington, DC: American Chemical Society

 

an encapsulation system with reduced flavor diffusion properties would be beneficial for the flavor industry

The flavor industry creates encapsulation systems to address various food

processing issues Analyzing an encapsulation system typically entails “in-use” tests which only demonstrate whether or not the encapsulation system provides a

benefit10 A typical “in-use” test consists of making an encapsulation containing a flavor The encapsulated flavor is then added to a food application and processed under normal cooking conditions These tests only provide a result which is negative

or positive Since the encapsulation system is a complex product no data is provided

on what aspect of the technology is providing the result Also, the food application is very complex and also affects how the encapsulation performs These facts leave the researcher asking “Have we created a better encapsulation or merely used the encapsulation in a more desirable environment?”

Analytical experiments, such as encapsulation-dissolution testing, have been created

to characterize the individual encapsulation systems in model food application

environments Valuable data has thus been obtained which can predict

encapsulation performance in various applications11 However, encapsulation

performance is highly dependent on capsule particle size, polymer barrier thickness, polymer permeability, capsule structure and encapsulation makeup Capsule

performance is measured, with account for all the variables that affect encapsulation performance

      

10 Mark, J.E.; Allcock, H.R.; West, R Inorganic Polymers 2nd ed Oxford University Press: New York,

NY, 2005.

11 Martin, C.A., (2003) Evaluating the Utility of Fiber Optic Analysis for Dissolution Testing of Drug

Products Dissolution Technologies, pg 37-39

Previously at the Givaudan Flavor Corporation attempts were made to study the

diffusion and permeability properties of hydrogel films containing clay12 Films

approximately 25 to 200 microns were cast and cross-linked with the appropriate

reagents The method produced wrinkled films and inconsistent film thicknesses that

only allowed for small pieces of the films to be analyzed The irregular films

produced irreproducible diffusion and permeability measurements The analytical

methodology used to characterize the films was tedious and involved the use of

multiple analytical techniques Each analytical technique contributed compounded

errors which affected the accuracy of the data

The primary goal of the present study is to create thin hydrogel films whose diffusion

and permeability properties can be measured easily with relative accuracy

Understanding flavor diffusion across thin hydrogel membranes will provide the basic

knowledge for hydrogel encapsulation development The films created were

approximately 20μm thick, which replicates typical coating thicknesses used in the

flavor industry Creating thin films can be challenging due to the following

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

The thin film hydrogels were characterized by micrometer film thickness

measurements, Environmental Scanning Electron Microscope (ESEM), swelling ratio

      

12 Vale, J.M (2004) Modification of Calcium Alginate Membranes with Montmorillonite Clay to Alter

the Diffusion Coefficient (Masters Thesis, University of Cincinnati, Department of Chemistry, 2004)

experiments and Thin Film Diffusion (TFD) – Ultraviolet-Visible (UV/VIS) analysis

1.1 Pectin: Sourcing, Manufacture and Functionality

Pectin and cellulose are abundant in fruits such as oranges, lemons, limes and

apples Pectin and cellulose associate creating a macromolecule called protopectin which binds or absorbs water Cellulose provides mechanical rigidity and pectin provides flexibility in the fruit and plant stock The mechanical properties of

protopectin allow the plant to weather environmental changes during seasonal

changes13

Large farming ventures and food companies process fruits such as oranges and apples, thus creating waste streams of citrus peel and apple pomace The waste streams are typically created in the regional areas where the crop is grown For instance, large waste streams of orange peel are created in Mexico, California and Florida The waste streams are collected and processed to yield valuable extracts such as pectin and cellulose

Pectin is produced worldwide by major manufacturing companies such as Cargill and

CP Kelco Extraction techniques performed on the citrus peel and apple pomace can

be altered to produce pectin with different functionalities Typically, the citrus peel or apple pomace is added to a hot acid solution where the protopectin undergoes

hydrolysis The hydrolysis step liberates the pectin from the cellulose The citrus peel or apple pomace is then separated from the hot acid solution by pressing, filtration and concentration processes The concentrated solution is added to ethanol where the pectin precipitates This precipitate is then washed, dried, and milled to a       

13 www.cargilltexturizing.com/products/hydrocolloids/pectins/cts_prod_hydro_pec_fun.shtml

specific particle size Processing conditions are constantly being modified and

optimized to meet specific customer needs14

Citrus peel and apple pommace processing allows for three types of pectin to be manufactured The hydrolysis processing step applied to citrus peel and apple

pomace alters the degree of esterification (DE) found in the pectin Thermodynamic properties such as glass transition temperature (Tg), melting point (Tm) and setting rates can be drastically altered by the degree of esterification Pectin with a DE value greater than 50 is referred to as high-methoxyl pectin (HM)15,16 Typical HM-pectin’s have a 55-85% degree of esterification and form thermostable gels in acidic pH

solutions containing 60% sugar HM-pectin is used to stabilize milk by reducing protein flocculation and enhancing beverage viscosities High-methoxyl pectin has other valuable uses such as minimizing ice crystal formation, thus enhancing

confectionary freeze-thaw properties Pectin with a DE value below 50 is referred to

as low-methoxyl pectin (LM) Typical LM-pectin’s have a 15-45% degree of

esterification and form thermoreversible gels under acidic or basic processing

conditions Thixotropic solutions for ice cream can be created using pectin pectin also has the ability to be crosslinked by divalent cations such as calcium and magnesium Crosslinked pectin typically becomes water insoluble and is useful for film and encapsulation purposes This pectin can also be extracted under basic conditions using ammonia producing amidated low methoxyl pectin (LMA) Typical       

LM-14 www.cargilltexturizing.com/products/hydrocolloids/pectins/cts_prod_hydro_pec_man.shtml

15 Sharma, B.R.; Dhuldhoya, N.C.; S.U Merchannt: U.C Merchant (2006) An Overview of Pectins

Times Food Procesing Journal, June-July Issue, 44-51

 

LMA-pectin’s have a 15-45% degree of esterification and a 5-25% degree of

amidation (DA) The addition of the amide groups to the pectin molecule changes the rheological properties and reduces pectin’s ability to be crosslinked by divalent cations LMA-pectin produces thermoreversible gels which are typically used in glazes and fruit preparations Many different forms of pectin can be created to meet specific customer needs The variety of pectin’s produced allows for new and

innovative consumer products to be developed

1.2 Pectin: Structure

Pectin is a natural polysaccharide containing up to1000 saccharide units in a like configuration Pectin molecules have a linear backbone composed of units of (1, 4)-linked α-D-galacturonic acid and its methyl ester17 Figure1.2-1 illustrates the

chain-basic structure of a pectin molecule

α-D-galacturonic acid

Methyl ester form of galacturonic acid

α-D-galacturonic acid

Methyl ester form of galacturonic acid

Figure 1.2-1: Structure of the pectin molecule

The galacturonic acid units may be in the salt form (galacturonate), which allows the pectin to be an anionic polymer The galacturonic acid residues can be esterified       

17 www.cpkelco.com/food/pectin.html

with methanol When 50% or more of the carboxyl groups contained in the polymer are methylated the pectin is considered high-methoxyl pectin This pectin is not cross-linkable with divalent cations and has limited uses for flavor encapsulation systems Less than 50% methylation produces pectin which is cross-linkable with divalent cations such as calcium12 Figure1.2-2 illustrates the basic structure of a calcium pectin molecule The pectin structure also contains L-rhamnose and

methylpentose The addition of these sugars to the pectin polymer structure creates

a branched molecule which has much reduced linearity The average molecular weight of pectin is typically 50,000 to 150,000 g/mol

-+ Ca +

+ Ca +

-+ Ca +

+ Ca +

+ Ca +

Figure 1.2-2: Structure of the calcium pectinate molecule

1.3 Alginate: Sourcing, Manufacture and Functionality

Seaweed has been used to obtain natural polymers such as alginate, agar and carrageenan over the last 50 years Alginate provides rigidity for the seaweed plant

      

 

by association with sodium chloride in ocean water Alginate also acts as a

humectant to reduce water loss in the plant in changing tidal conditions18 Alginate is found in the Phaeophycaea brown algae family Seaweed varieties such as

Macrocystis pyrifera, Ascophyllum Nodosum and Laminaria are useful for alginate production19 Comercially important seaweed is typically harvested in the coastal waters of California, Australia, Norway and Japan Seaweed from different coastal regions produces alginate with different properties due to structural differences in the extracted polymer

The manufacturing process to obtain alginate begins with harvesting seaweed in the desired coastal region Boats are built to a special design to skim the ocean surface and retrieve the top three feet of the seaweed plant The harvested seaweed is gently dried and milled to desired specifications for optimal processing The milled seaweed is then added to hot water and sodium carbonate under mixing conditions The caustic treatment allows the seaweed to swell and form a viscous solution The highly viscous solution is diluted and the insoluble residues are removed Chlorine is added to the liquid fraction 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 desired customer specifications20,21

      

18 Cosgrove, D.J., (2005) Growth of the plant cell wall Molecular Cell Biology, 5, pg 850-861

19 www.cargilltexturizing.com/products/hydrocolloids/alginates/cts_prod_hydro_alg_raw.shtml

20 www.cargilltexturizing.com/products/hydrocolloids/alginates/cts_prod_hydro_alg_man.shtml

Alginate is generally used as a cold-setting gel that is thermally stable when

crosslinked The food industry typically uses alginate as a viscosity control agent for products such as jellies, jams, pastes, beverages, soups and ice-cream22,23,24

Industries such as pharmaceutical and biomedicine companies use alginate to

encapsulate drugs and cellular materials25 Alginate has also been used to

dehydrate products such as paper and textiles, as flame retardants for fabrics, and as blood detoxifiers

22 Huajuan, L.; Koichi, A.; Inakuma, T.; Yamauchi, R and Kato, K (2005) Physical properties of

water-soluble pectins in hot and cold break tomato pastes Food Chemistry, 93 (3), pg 403-408

23 Paraskevopoulou, A.; Boskov, D and Kiosseoglou, V (2005) Stabilization of olive oil-lemon juice

emulsion with polysaccharides Food Chemistry, 90 (4), pg 627-634

24 Kailasapathy, K and Sellepan, C.D (1998) Effect of single and integrated emulsifier-stabilizer on

soy-ice confection Food Chemistry, 63 (2), pg 181-186

25

  Milanovanovic, A.; Bozic, N and Vujcic Z (2007) Cell wall invertase immobilization within calcium

alginate beads Food Chemistry, 104 (1), pg 81-86

26 www.cargilltexturizing.com/products/hydrocolloids/alginates/cts_prod_hydro_alg_mol.shtml

alginates27 High-G alginates typically produce gels that are strong and exhibit good heat stability However, the gels are brittle and this can create a product with little impact strength Alginates containing large percentages of mannuronic acid content are called 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

of localized crystallization when glucuronic acid units are crosslinked with divalent cations28 Figure 1.4-2 illustrates alginate glucuronic and mannuronic block types

Figure 1.4-2: Alginate block types

The divalent cation fits into the D-glucuronic acid block structure like eggs in an egg box This binds the alginate polymers together by forming junction zones which

      

27 Sime, Wilma J., (1990) Alginates Limewood, Raunds, Northhamptonshire NN9 6NG, UK p 53-60

28 www.fmcbioploymer.com/food/ingredients/Alginates/PGA/Introduction/tabid/2410/fault/aspx

results in gelation29 Figure 1.4-3 illustrates the calcium binding site of D-glucuronate and Figure 1.4-4 illustrates the egg box structure of calcium crosslinked alginate

Guluronate Guluronate

Guluronate Guluronate

Figure 1.4-3: Calcium binding site in polyguluronate dimer

Figure 1.4-4: Calcium alginate cross- linked “Egg box” model

2 Experimental Section

2.1 Experimental Objectives

The objectives of the present work are as follows:

a) Prepare uniform films of calcium alginate reproducibly in a 5 to 50μm

      

29 www.fmcbioploymer.com/food/ingredients/Alginates/PGA/Introduction/tabid/2412/fault/aspx. 

thickness range

b) Prepare uniform films of calcium pectinate reproducibly in a 5 to 50μm

thickness range

c) Analytically measure the diffusion of benzaldehyde across the hydrogel

barriers to determine permeability and diffusion coefficients

2.2 Raw Materials

1 Sodium alginate extracted from brown seaweed (Phaeophyceae) was chosen

to create thin films The sodium alginate is cross-linkable with divalent cations such as Ca2+ and Mg2+ The material is a whitish tan powder containing 1 to 3% moisture The average molecular weight is 75,000 g/mol The sodium alginate trade name is Keltone LV and was supplied by ISP (International Specialty Products) 1361 Alps Road, Wayne, New Jersey 07470

2 Pectin extracted from lemon peel was chosen to create additional thin films The pectin is also cross-linkable with divalent cations such as Ca2+ and Mg2+ The material is a white powder containing approximately 3 to 4% moisture and average molecular weight was 95,000 g/mol The pectin trade name is TIC Gum-32 and was supplied by TIC Gums, 4609 Richlynn Drive, Belcamp, MD

21017

3 Calcium chloride was used as the crosslinking material for sodium alginate and pectin The material is a white granular powder containing approximately 2% moisture The calcium chloride was supplied by the Givaudan Flavor Corporation, 1199 Edison Drive, Cincinnati, Ohio 45126

4 Benzaldehyde was used to measure diffusion across the calcium alginate and calcium pectin films The benzaldehyde was 98% pure with a boiling point of 435.1 K Benzaldehyde has a Log P value of 1.78 which is considered to be relatively water soluble in the flavor industry The benzaldehyde was supplied

by the Givaudan Flavor Corporation, 1199 Edison Drive, Cincinnati, Ohio

45126

       

O

Benzaldehyde  

Figure 2.2-1: Structure of benzaldehyde

5 Miglyol 812 (Medium chain triglycerides) was used to prepare dilute

benzaldehyde solutions It is an oxidative-stable vegetable oil which was supplied by Givaudan Flavor Corporation 1199 Edison Drive, Cincinnati, Ohio

45126

2.3.1 Film Sheet Preparation

Three Baker’s Secret medium cookie sheets were purchased from a local grocery store The measurements of the cookie sheets were 43.2cm X 27.9cm X 1.9cm with

an estimated surface area of 1205.3 cm2 The cookie sheets were lightly scuffed under water with an abrasive sponge to partially remove the Teflon™ coating from