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Encapsulation andControlled ReleaseTechnologies in FoodSystemsEDITED BY
Jamileh M. LakkisExpert in encapsulation and controlled release technologiesBarcelonaSpain
SECOND EDITION
This edition first published © 2016 by John Wiley & Sons Ltd
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1 2016
Contents
List of contributors, xiii
Foreword, xvii
Preface to second edition, xix
Preface to first edition, xxi
1 Introduction, 1Jamileh M. Lakkis
Wall-forming materials, 2
Core materials, 2
Release triggers, 2
Payload, 2
Current approaches to encapsulation and controlled release, 3
Entrapment in carbohydrate matrices, 3
Complexation into cyclodextrins, 6
Encapsulation in microporous matrices: physical adsorption, 6
Encapsulation in fats and waxes, 7
Encapsulation in emulsions and micellar systems, 7
Encapsulation in coacervated polymers, 8
Encapsulation using supercritical fluids, 9
Encapsulation into hydrogel matrices, 9
Encapsulation using flow-focusing technology, 10
Overview of controlled-release systems, 11
Matrix systems, 11
Reservoir systems, 12
Combination systems, 12
Release mechanisms, 13
References, 13
2 Encapsulation of edible active compounds using supercritical fluids, 16Salima Varona, Ángel Martín and María José Cocero
Supercritical fluid technology, 16
Properties of supercritical fluids, 16
Implementation of processes using SCFs: Basic considerations, 17
Current industrial applications, 18
Particle formation processes, 19
SCFs as solvents, 19
SCFs as antisolvents, 20
SCFs as solutes, 22
SCFs as propellants, 22
Products, 24
vii
viii Contents
Single compound products, 24Co-precipitation and encapsulation processes: Carrier materials, 25Encapsulation of solid active compounds, 26Encapsulation of liquid active compounds, 27
Case study: Encapsulation of lavandin essential oil, 29Encapsulation in water-soluble carriers, 30Encapsulation in water-insoluble carriers, 32Impregnation, 33Comparison with alternative encapsulation technologies, 34
References, 36
3 Encapsulation by complex coacervation, 41Curt Thies
Introductory comments, 41Complex coacervation background and terminology, 42Biopolymers and complex coacervation, 43
Biopolymer structure and properties, 43Milk and vegetable protein denaturation, 48Reproducibility issues, 49Concluding biopolymer comments, 51
Stabilization and solidification of complex coacervate capsule shells, 52Overview, 52mTGase treatment of complex coacervate capsule shells, 53
Overview of current encapsulation protocols, 59Concluding comments, 71References, 71
4 Lyophilized liposomes for food applications: Fundamentals,processes, and potential applications, 78Taise Toniazzo and Samantha C. Pinho
Introduction, 78Liposomes: Structure, production methods, and applications in foods, 79Formulation factors affecting liposome integrity after lyophilization, 84Influence of the lyophilization process parameters and technologicalfactors on the lyophilized product, 89Concluding remarks and future perspectives, 90References, 91
5 Microencapsulation of probiotics, 97Thierry F. Vandamme, Gildas K. Gbassi, Trinh Lan Nguyen and Xiang Li
Introduction to probiotics, 97Definitions, applications, and advantages of probiotics, 97
Introduction to microencapsulation, 99Definition, 99Purpose of microencapsulation, 100Structural details of microcapsules, 100Materials used in the microencapsulation of probiotics, 102Factors affecting the microencapsulation effectiveness of probiotics, 114
Methods used in microencapsulating probiotics, 115
Contents ix
Extrusion technique for microencapsulation, 115Emulsion technique, 115Use of drying technology for microencapsulating Probiotics, 117Interfacial polymerization and coacervation, 119Co-crystallization method, 120Molecular inclusion, 120Centrifugal extrusion technique, 120
Conclusion and prospects, 121References, 121
6 Emulsions as delivery systems in foods, 129Ingrid A.M. Appelqvist, Matt Golding, Rob Vreeker and Nicolaas Jan Zuidam
Introduction, 129Stabilization and destabilization of emulsion systems, 130
Emulsion stabilization, 130Formulation design for food emulsions, 135
Release triggers for emulsions, 142Delivery of water-soluble food actives via emulsions, 143
Water-in-oil emulsions for controlling water-soluble actives, 143Effect of O/W emulsions on taste release and perception, 143Double emulsions for controlling water-soluble actives, 145
Delivery of hydrophobic food actives via O/W emulsions, 149Lipophilic health ingredients in O/W emulsions, 149Aroma release from O/W emulsions, 149Structured emulsions in hydrogels for controlled release of aromas, 153
Delivery of dietary fats as O/W emulsions and their protection againstoxidation, 155Future trends, 159
Nature-made emulsions, 159Monodispersed emulsions, 163
References, 164
7 Improved solubilization and bioavailability of nutraceuticals innanosized self-assembled liquid vehicles, 173Nissim Garti, Eli Pinthus, Abraham Aserin and Aviram Spernath
Introduction, 173U-Type microemulsions, swollen micelles, and progressive and fulldilution, 177Solubilization of nonsoluble nutraceuticals, 179
Lycopene, 180Phytosterols, 185Lutein and lutein ester, 187
Oxidative stability, 191Bioavailability, 192
CoQ10 and Improved Bioavailability, 192Water binding, 195Conclusions, 197References, 198
x Contents
8 Encapsulation and controlled release in bakery applications, 204Jamileh M. Lakkis
Introduction, 204
Encapsulation technologies for bakery applications, 205
Hot melt particle coating technology, 205
Spray congealing/chilling, 207
High pressure congealing (beta process), 209
Film-forming materials, 210
Waxes, 210
Resins, 212
Glycol polymers, 212
Fats and glycerides, 212
Lauric acid group, 212
Palmitic acid group, 213
Oleic/linoleic acid group, 213
Characteristics of wax and fat coating materials, 213
Ideal properties of encapsulated particles for bakery applications, 216
Good barrier properties, 216
Mechanical strength, 216
Surface morphology, 217
Adhesion and cohesiveness, 217
Particle size distribution, 217
Film thickness, 217
Melting properties, 217
Applications of encapsulated actives in bakery applications, 218
Leavening systems, 218
Encapsulated sweeteners, 222
Encapsulated antimicrobial agents, 224
Encapsulated minor ingredients, 229
Flavors, 229
Encapsulated nutrients, 229
References, 230
9 Encapsulation and controlled release applications in confectioneryand oral care products, 236Jamileh M. Lakkis
Introduction, 236
Physiology and organization of the oral area, 237
Permeability and barrier functions of the oral cavity, 239
Membranes – physiology and transport routes (Plasma and Epithelialmembranes), 239
Plasma membranes, 239
Epithelial membranes, 240
Oral mucosa, 240
Saliva, 242
Keratinization, 242
Contents xi
Polarity, 243pH, 243
Transport mechanisms across membranes, 244Delivery sites in the oral cavity, 245
Advantages of the oral route for drug delivery, 247Disadvantages of oral route delivery, 248
Dosage formulation, 249Physico-chemical properties of the active and dosage, 249
Confectionery products as delivery systems, 249Chewing gum as a delivery system, 249
Typical gum composition and manufacture, 250Chewing gums for delivering flavors and non-medicated actives, 252
Effect of saliva flow rate on flavor release, 254Effect of non-sugar sweeteners (Polyols), 255Effect of sensates on flavor release from chewing gum, 256
Chewing gum for delivering cosmetic and medicated actives, 257Oral and dental health (Antimicrobials, Dental Caries Prevention,Xerostomia), 257
Antimicrobials, 257Chewing gums for delivering actives for minor pains, diabetes andweight management, 262Chewing gum for delivering caffeine, 262Chewing gums for delivering nicotine, 263Chewing gum for delivering acetyl salicylic acid, 265Chewing gum for delivering insulin, 265Lozenges as delivery systems, 266
Lozenges for delivering flavors and sensates, 267Lozenges for delivering relief from cough and sore throat, 268Lozenges as delivery systems for oral care, 269Lozenges for delivering nicotine (Smoking Cessation), 270
Oral thin films, 271Seamless capsules, 274References, 276
10 Assessing bioavailability and nutritional value ofmicroencapsulated minerals, 289Diego Moretti and Michael Zimmermann
Introduction, 289Assessing bioavailability and nutritional value of minerals for human use, 291
In vitro methods, 293Animal studies, 295Studies in human subjects using tracers, 297Intervention studies in humans, 300
Special considerations in evaluating the bioavailability of encapsulatedminerals, 303
Solubility of the coating material in the GI tract, 303Coating material as a functional ingredient, 303
xii Contents
Outlook and research questions, 304References, 304
11 Effects of microencapsulation on bioavailability of fish oil omega-3fatty acids, 309Philip Christophersen, Mingshi Yang and Huiling Mu
Introduction, 309Chemistry of omega-3 fatty acids, 310Functional foods enriched with omega-3 fatty acids, 312Bioavailability of omega-3 fatty acids, 312
Effect of chemical structure, 314Effect of microencapsulation on bioavailability of omega-3 fatty acids, 315
Conclusions, 324References, 325
12 Innovative applications of micro and nanoencapsulation in foodpackaging, 333Murat Ozdemir and Tansel Kemerli
Introduction, 333Antimicrobial food packaging materials and controlled releaseapplications, 335
Antimicrobials-organic acids, peptides, essential oils, 344Antimicrobial essential oils, 347Metals and metal oxides, 348Insect and rodent repellents, 351
Scented fragrance inserts and aroma-flavor releasing systems, 353Encapsulated pigments and fillers, 357Encapsulated inks and time-temperature indicators, 362
Future perspective, 368References, 369
Index, 379
List of contributors
Ingrid, A.M. AppleqvistCSIRO, Sydney, Australia
Abraham AserinCasali Institute of Applied Chemistry, The Institute of Chemistry,
The Hebrew University of Jerusalem, Jerusalem, Israel
Philip C.B. ChristophersenDepartment of Pharmacy, Faculty of Health and Medicinal Sciences,
University of Copenhagen, Denmark
María José CoceroDepartment of Chemical Engineering and Environmental Technology,
University of Valladolid (Spain), Valladolid, Spain
Nissim GartiCasali Institute of Applied Chemistry, The Institute of Chemistry,
The Hebrew University of Jerusalem, Jerusalem, Israel,
Nutralease Ltd, Mishor Adumim, Israel
Gildas K. GbassiUniversité Felix Houphouët Boigny, Département of de Chimie Analytique,
Chimie Générale et Minérale, Abidjan, Cote d’Ivoire
Matt GoldingMassey University, Palmerston North, New Zealand
Nicolaas Jan ZuidamUnilever Food and Health Research Institute, Unilever R&D Vlaardingen,
The Netherlands
Tansel KemerliDepartment of Chemical Engineering, Section of Food Technology, Gebze Institute of
Technology, Turkey
Jamileh M. LakkisExpert in encapsulation and controlled release technologies, Barcelona, Spain
xiii
xiv List of contributors
Xiang LiUniversité de Strasbourg, Faculté de pharmacie, Laboratoire de Conception et
d’Application de Molécules Bioactives, Illkirch Cedex, France
Ángel MartínDepartment of Chemical Engineering and Environmental Technology,
University of Valladolid, Valladolid, Spain
Diego MorettiETH Zürich, Department of Health Sciences and Technology, Institute of Food Nutrition
and Health, aboratory of Human Nutrition Schmelzbergstrasse, Zürich, Switzerland
Huiling MuDepartment of Pharmacy, Faculty of Health and Medicinal Sciences,
University of Copenhagen, Denmark
Trinh Lan NguyenUniversité de Strasbourg, Faculté de pharmacie, Laboratoire de Conception et
d’Application de Molécules Bioactives, Illkirch Cedex, France
Murat OzdemirDepartment of Chemical Engineering, Section of Food Technology, Gebze Institute of
Technology, Turdey
Samantha C. PinhoDepartment of Food Engineering, School of Animal Science and Food Engineering
(FZEA), University of São Paulo, Brazil
Eli PinthusNutralease Ltd, Mishor Adumim, Israel, Adumim Food Ingredients,
Mishor Adumim, Israel
Aviram SpernathCasali Institute of Applied Chemistry, The Institute of Chemistry,
The Hebrew University of Jerusalem, Jerusalem, Israel
Curt ThiesThies Technologies, Henderson, Nevada
Taise ToniazzoDepartment of Food Engineering, School of Animal Science and Food Engineering,
University of São Paulo, Brazil
List of contributors xv
Thierry F. VandammeUniversité de Strasbourg, Faculté de pharmacie, Laboratoire de Conception et
d’Application de Molécules Bioactives, Illkirch Cedex, France
Salima VaronaDepartment of Chemical Engineering and Environmental Technology,
University of Valladolid, Valladolid, Spain
Rob VreekerUnilever Food and Health Research Institute, Unilever R&D Vlaardingen,
The Netherland
Mingshi YangDepartment of Pharmacy, Faculty of Health and Medicinal Sciences,
University of Copenhagen, Denmark
Michael ZimmermannETH Zürich, Department of Health Sciences and Technology, Institute of Food Nutrition
and Health, Zürich, Switzerland
Foreword
The biggest threat to the wider utilization of encapsulated ingredients in food formu-lations is the use of MIRAGE ENCAPSULATION. This unfortunate practice used by afew marginal suppliers, who resort to dry blending actives with excipients and labelthem as “encapsulated” ingredients, results in low-quality products which cast doubtson the benefits of true encapsulation.
xvii
Preface to second edition
The emergence of the discipline of encapsulation and controlled release has undoubt-
edly had a great impact on the food and dietary supplements sectors. However, a large
gap still exists between the theoretical aspects of encapsulation and controlled release
technologies and their potential applications.
This book edition represents a continued effort to bridge this gap. It is designed as
an improvement and a complement to the first edition which was published in 2007.
This edition differentiates itself in two main aspects. First, it introduces the reader
to novel encapsulation and controlled release technologies which have not yet been
addressed by any existing book on this matter, and second, it incorporates an elabo-
rate discussion on the impact of encapsulation and controlled release technologies on
the bioavailability of a select group of health ingredients. Similar to the first edition,
this book includes chapters written by distinguished authors and researchers in their
respective areas of specialization.
Chapters in this edition, except for two of them, are either entirely new or have
been appropriately expanded:
• Chapter 1 provides a general introduction to microencapsulation and controlled
release technologies, mainly those adaptable to food applications. It also discusses
briefly the concept of release kinetics and modes of release.
• Chapter 2 authored by Dr. Cocero and co-workers discusses a novel approach to
microencapsulation using supercritical fluid (SCF) technology. The chapter pro-
vides an elaborate discussion on particle formation processes using CO2-SCFs along
with a case study highlighting the benefits and challenges of microencapsulating
essential oils using such novel technologies.
• Chapter 3 by Dr. Curt Thies presents an expanded version of the original chapter
on encapsulation via complex coacervation. It provides a critical assessment of for-
mulations on yield and stability of encapsulated food grade oils (orange, omega-3
fatty acids).
• Chapter 4 by Dr. Pinho and Dr. Toniazzo introduces the reader to a new approach
to microencapsulation via dried liposomes. The authors also discuss the potential
of dried liposome microcapsules as a safer alternative to wet systems, especially for
food applications.
• Chapter 5 by Dr. Thierry Vandamme and his collaborators presents an overview
of the role of excipients and encapsulating agents in preserving the stability and
viability of encapsulated probiotic bacteria.
• Chapters 6 by Dr. Klaas Jan Zuidam et al. dealing with emulsions as delivery
systems and Chapter 7 by Professor Garti et al. on Nanosized Self-Assembled
Liquid Vehicles have not been updated but are included in this edition due to
the importance of the subject matters to the concepts of microencapsulation and
controlled release.
xix
xx Preface to second edition
• Chapter 8 written by the editor of this book (Dr. Lakkis) on encapsulation and con-trolled release applications in bakery products has been updated to include broaderdiscussions and additional illustrations.
• Chapter 9 also authored by the book editor has been rewritten to highlight novelapproaches for delivering flavors, health as well as oral care actives via confec-tionery products.
• Chapter 10 is written by two leading experts on bioavailability of minerals,Dr. DiegoMoretti and Dr. Michael Zimmermann. This chapter presents an in-depthdiscussion on methods for assessing bioavailability and nutritional value ofmicroencapsulated minerals.
• Chapter 11 by Dr. Mu and collaborators presents a critical overview of currentadvances in assessing the impact of microencapsulation techniques on stabilizingomega-3 fatty acids and preserving their bioavailability.
• Chapter 12 by Dr. Murat Ozdemir and Dr. Tansel Kemerli includes an expandedupdate on novel technologies for controlling the release of scents and fragrances,pigments, inks and time-temperature indicators in food packaging applications.
It is my hope that this new edition proves itself to be a useful source of informationonmicroencapsulation and controlled release technologies, mainly for those involvedin using them in the development of new products. A special effort was made to keepthe text accurate, clear, and easy-to-read.
This new edition would not have been possible without the commitment andcooperation of the contributing authors who I am deeply indebted to. Thank you.
I also would like to acknowledge David McDade (excutive editor), Audrie Tan(project manager), and Anupama Kumari (project manager) and the editorial staff atWiley-Blackwell, and also Jo Egré (freelance copy editor) for their continued support,advice, and patience throughout this project
As always I am very grateful for the readers of the first edition and welcome theircontinued feedback on this book.
Jamileh M. Lakkis
Preface to first edition
Encapsulation and controlled release technologies have enjoyed their fastest growthin the last two decades. These advances, pioneered by pharmaceutical companies,were a result of: (1) the rapid change in drug development strategies to target specificorgans or even cells, (2) physicians’ growing concern about patient non-compliance,and (3) pharmaceutical companies desire to extend their market monopoly on newdrugs for a certain period of time, as provided by the US and international patent laws.
Despite this progress, encapsulation and controlled release technologies have onlybeen recently adopted by the food industry. Food researchers and technologists haveoften been confronted with the dilemma of how to translate all these advances fromthe drug arena into practical applications in food systems. By searching the literature,one can find volumes of books and specialized publications on encapsulation andcontrolled release technologies. Unfortunately, most of these publications have dealtwith theoretical aspects of these technologies, with little emphasis on real applicationsin consumer and food products.
This book attempts to illustrate various aspects of encapsulation and controlledrelease applications in food systems using practical examples. These examples willgive the reader an appreciation for the delicate art of designing encapsulated ingre-dients and the enormous challenges in incorporating them into food formulations.Most of the practical examples in this book were borrowed from the patent literature.This approach might be questioned based on the fact that patents applications arenever peer reviewed, but seems justifiable considering the frantic effort by both indus-try and academia to protect their discoveries and to gain limited-time monopoly ontheir innovations, thus limiting the availability of such information in peer-reviewedarticles.
This publication has several potential uses. It is a reference book for scientistsin the food, nutraceuticals, and consumer products industries who are looking tointroduce microencapsulated ingredients into new or existing formulations. It is alsoa post-graduate text designed to give students some comprehension of various aspectsof encapsulation and controlled release in food systems.
This book is organized in such away that each chapter treats onemajor applicationof encapsulation and controlled release technologies in foods.
Chapter 1 introduces the readers to various encapsulation and controlled releasetechnologies, as well as release mechanisms, suitable for applications in foods,nutraceuticals, and consumer products.
Chapter 2 by Professor Nissim Garti and his collaborators discusses a novelapproach to encapsulation and controlled release via reverse microemulsion tech-nique referred to as nanosized self-assembled liquids (NSSL). Such systems areshown to provide exceptional thermodynamic stability in a wide pH range. Inaddition to enhancing bioavailability of functional active ingredients, NSSL systems,by virtue of their unique transparent appearance, are excellent candidates forbeverage applications.
xxi
xxii Preface to first edition
Chapter 3, by Dr. Klaas-Jan Zuidam and co-workers, presents an elaborate
approach to understanding emulsions and their benefits as delivery systems in food
applications. This chapter discusses various mechanisms of emulsion stabilization
and destabilization and how they can best be designed for targeted delivery of flavors
and functional ingredients in the human gastrointestinal system.
Chapter 4 on encapsulation and controlled release of probiotics by Drs. Chen and
Chen reports on approaches for encapsulating probiotic bacteria in dairy products as
well as in the human gastrointestinal tract. This chapter also discusses novel optimiza-
tion techniques for stabilizing these beneficial bacteria and enhancing their survival
rates.
Chapter 5, written by the editor of this book, highlights current approaches to
encapsulation and controlled release technologies for bakery products applications.
Current encapsulation practices such as hot-melt particle coating and spray chilling
are discussed. Examples of the performance of encapsulated leavening agents as well
as sweeteners and flavors are presented in shelf-stable bakery applications.
Chapter 6 on nanoencapsulation technology by Dr. Huang and his collabora-
tors deals with novel approaches to encapsulate enzymes and nutraceuticals. Spe-
cific examples are presented on stabilization of phytochemicals and their enhanced
bioavailability via incorporation into nanoemulsions and bioconjugation systems.
Chapter 7 on flavor encapsulation via complex coacervation is written by
Dr. Curt Thies. Discussion is focused on the basic principle of complex coacervation
technique as a liquid–liquid polymer phase separation phenomenon. Guidance on
polymer selection and subsequent implications on the physicochemical properties of
capsules as well as their release behavior is provided.
Chapter 8, written by the editor of this book, details techniques used for deliver-
ing therapeutic as well as functional actives and flavors via confectionery products.
Technologies and subsequent applications discussed in this chapter have wide appli-
cations in food and nutraceuticals, as well as in pharmaceutical arenas. Mechanisms
and challenges specific to targeted release in upper gastrointestinal tract, especially
the mouth and throat areas, will be described in great detail.
Chapter 9 discusses encapsulation and controlled release of actives in packaging
applications by Dr. Ozdemir and collaborator. In this contribution, the authors pro-
vide examples on embedding fragrances, pigments as well as antimicrobial and insect
repellent agents into food packaging films.
Chapter 10, authored by Ms. Kathy Brownlie, provides a marketing perspective
of microencapsulation technologies and their potential impact on the food industry.
Ms. Brownlie offers an in-depth assessment of market drivers as well as constraints
that are still hindering wider implementation of these technologies in food manufac-
turing.
This book has definitely surpassed my vision and expectations thanks to the con-
tributors and I am grateful to all of them for their expertise, commitment, and dedi-
cation. It is my hope that this book will prove itself a useful source on encapsulation
and controlled release in a wide range of food and consumer product applications.
Many thanks to the editorial staff at Blackwell Publishing Co., especially to Mark
Barrett and Susan Engelken, for their valuable help and advice throughout this
project.
Preface to first edition xxiii
Last but not least, I would like to thankmy parents who taughtme the importanceof working hard, having clear goals, and standing for what I believe is right. It is alesson that guides me in everything I do.
Jamileh M. Lakkis
CHAPTER 1
IntroductionJamileh M. Lakkis
Encapsulation and controlled-release systems are designed to protect actives fromundergoing undesirable interactions while enhancing their functionality andbioavailability. Other objectives include masking the taste of bitter components,ensuring adequate administration of heat- or oxidation-labile health actives, andensuring their delivery at a predetermined rate to a target site. In foods andnutraceuticals, encapsulation and controlled release have found applications inmany categories such as confections, bakery, breakfast cereals, dairy products,beverages, packaging, among others. Markets and Markets Research estimated thevalue of food-related encapsulation market to reach $39.5 billion by 2020 (http://www.marketsandmarkets.com).
European Directive 3AQ19a defined controlled release as a “modification of the rateor place at which an active substance is released.” Such modification can be madeusing materials with specific barrier properties for manipulating the release of theactive and to provide unique sensory and/or functional benefits.
The addition of small amounts of nutrients to a food system may not affect itsappearance and taste significantly; however, incorporating high levels of nutrientsto meet certain requirements or treat an ailment will most often result in unstableand unpalatable foods. Examples of such nutrients include fortification with calcium,vitamins, or polyunsaturated fatty acids, which often results in undesirable sensorychanges such as grittiness, medicinal or oxidized taste, and others. Different typesof encapsulation and controlled-release systems are currently available to help over-come these challenges and to provide a wide range of release requirements.
A wide variety of cores (encapsulants), wall-forming materials (encapsulatingagents), and technologies are commercially available for manufacturing microcap-sules andmicroparticles of different sizes, shapes, morphological properties, and costs,as well as controlling the release of the encapsulated actives.
Encapsulation and Controlled Release Technologies in Food Systems, Second Edition.Edited by Jamileh M. Lakkis.© 2016 John Wiley & Sons, Ltd. Published 2016 by John Wiley & Sons, Ltd.
1
2 Chapter 1
Wall-forming materials
Materials used in microencapsulation as film coating or matrix-forming componentsinclude several categories:1 Lipids and waxes: beeswax, candelilla and carnauba waxes, wax microemulsionsand macroemulsions, glycerol distearate, and natural and modified fats
2 Proteins: gelatins, whey proteins, zein, soy proteins, caseins and caseinates, gluten,etc. All these proteins are available in both native and modified forms.
3 Carbohydrates: starches, maltodextrins, chitosan, sucrose, glucose, ethylcellulose,cellulose acetate, alginates, carrageenans, chitosan, etc.
4 Food-grade polymers: polypropylene, polyvinylacetate, polystyrene, polybutadi-ene, etc.
Core materials
These materials include flavors, antimicrobial agents, vitamins, minerals, antiox-idants, probiotics, colors, acidulants, alkalis, buffers, sweeteners, enzymes, cross-linking agents, yeasts and chemical leavening agents, omega-3 fatty acids, and othernutrients.
Release triggers
Encapsulation and controlled-release systems can be designed to respond to one or acombination of triggers that can activate the release of the entrapped substance andto meet a desired release target or rate. Triggers can be one or a combination of thefollowing:1 Temperature: ideally for release of actives from fat/waxmatrices, gelatin, and othermeltable polymers
2 Moisture: essential for releasing actives entrapped in hydrophilic matrices3 pH: can release actives from enteric-coated particulates or emulsions (coalescence)4 Enzymes: can release actives from enteric-coated particulates due to disintegrationof the wall material with amylases, proteases, lipases, etc.
5 Shear: chewing, physical fracture, and grinding represent physical means forrelease of actives during actual consumption
6 Lower critical solution temperature: release takes place at a critical temperaturebelow which the components of a mixture are miscible for all compositions (oftenencountered in phase diagrams).
Payload
Payload is a term used to estimate the amount of active (core) entrapped in a givenmatrix or wall material (shell) and is expressed as:
Payload (%) = [(core)∕(core + shell)] × 100
Introduction 3
Current approaches to encapsulationand controlled release
Entrapment in carbohydrate matricesEncapsulation into a carbohydrate matrix generally involves melting a crystallinepolymer using heat and/or shear to transform the molecular structure into anamorphous phase. The encapsulant is then incorporated into the meta-stableamorphous phase followed by cooling to solidify the structure and form glass, thusrestricting molecular movements.
Carbohydrates are excellent candidates for this type of encapsulation due toseveral attributes; they (1) form an integral part of many food systems, (2) arecost-effective, (3) occur in a wide range of polymer sizes, and (4) have desirablephysicochemical properties such as solubility, melting, phase change, etc.
Sucrose, maltodextrins, native and modified starches, polysaccharides, and gumshave been used for encapsulating flavors, minerals, vitamins, probiotic bacteria, aswell as pharmaceutical actives. The unique helical structure of the amylose molecule,for example, makes starch a very efficient vehicle for encapsulating lipids and flavors(Conde-Petit et al., 2006). Some carbohydrates such as inulin and trehalose can pro-vide additional benefits for encapsulation applications; inulin is a prebiotic that canenhance the survival of probiotic bacteria, while trehalose serves as support nutrientfor yeasts.
Two main technologies—spray-drying and extrusion—are commonly used inlarge-scale encapsulation applications into amorphous matrices, although differentmechanisms are used. In spray-drying, the active is entrapped within the porousmembranes of hollow spheres, while in extrusion, the goal is to entrap the active ina dense, impermeable glass.
Encapsulating actives via spray-drying requires emulsifying the substrate into theencapsulating agent. This is especially important for flavor applications, consideringthe fact that most flavors are made of components of various chemistries (e.g., polar-ity, hydrophobic-to-hydrophilic ratios), thus limiting their stability when dispersed orsuspended in different solvents. Hydrophobicity is one of the most critical attributesthat can play a significant role in determining flavors payload as well as their releasein food systems.
The basic principle of spray-drying can be found in an excellent book by Masters(1979). Briefly, the process comprises atomizing a micronized (1- to 10-μm dropletsize) emulsion or suspension of an active and an encapsulating substance(s) and fur-ther spraying into a chamber. Drying takes place at relatively high temperatures (210oC inlet and 90 oC outlet), although the active’s exposure to these temperatures lastsonly few seconds. The process results in free flowing, low bulk density powders of10 to 100 μm. Optimal payloads of 20% can be expected for flavors encapsulated instarch matrices. Maltodextrins and lower molecular weight sugars, due to their lowviscosities and inadequate emulsifying activities, often lead to lower flavor payloads.
Several factors can impact the efficiency of encapsulation via spray-drying,—mainly, those related to the emulsion or dispersion (e.g., solid content, molecularweight, emulsion droplet size, viscosity) and to the process (e.g., feed flow rate,inlet/outlet temperatures, gas velocity). Release of flavors from spray-dried matrices
4 Chapter 1
takes place on reconstitution of the dried emulsion in the release medium (water orsaliva). Reasonable prediction of the release behavior should take into considerationthe complex chemistry of flavors and prevailing partition and phase transportmechanisms between aqueous and nonaqueous phases (Larbouss et al., 1992;Shimada et al, 1991).
Encapsulation into an amorphous matrix via extrusion has gained wide popu-larity in the past two decades with applications ranging from entrapping flavors fortheir controlled release to masking the grittiness of minerals and vitamins. Hot meltextrusion is a process with many unique advantages for encapsulation applications,namely:1 Extruders are multifunctional systems (many unit operations) that can be manip-ulated to provide desired processing temperature and shear rate profiles by varyingscrew design, barrel heating, mixing speed, feed rate, moisture content, plasticizers,etc.
2 There is the possibility of incorporating actives and other ingredients at differentpoints of the extrusion process. Heat-labile actives, for example, can be incorpo-rated via temperature-controlled inlets toward the end of the barrel, and theirresidence time in the extruder can be minimized to avoid degradation of the activeand preserve its integrity.
3 Extruders are also formers; encapsulated products can be recovered in practicallyany desired shape or size (pellets, rods, ropes, etc.).
4 Only a very limited amount of water is needed to transform carbohydrates fromnative crystalline to amorphous glassy matrices in an extruder, thus limiting theneed for expensive downstream drying.
5 High payload can exceed 30%when encapsulating solid actives in extruded pellets.6 Favorable economics due to the high throughput, continuous mode, and limitedneed for drying make extrusion a very attractive process for manufacturing encap-sulated ingredients.Figure 1.1 shows a typical melt extrusion encapsulation process. The carbohy-
drate (encapsulating matrix), a mixture of sucrose and maltodextrin, is dry fed andmelted via a combination of heat and shear in the extruder barrel so that the crys-talline structure is transformed into an amorphous phase. The encapsulant (flavor orother active) is added through an opening in a cooled barrel situated toward the dieend of the barrel to avoid flashing off of low boiling components. The amorphousmixture exits the die in the form of a rope that can be cooled quickly by air or liquidnitrogen to form a solid glassy material. The latter can be ground to a desired parti-cle size to form compact microparticles of high bulk density. Using this technology,encapsulated products can be designed to achieve almost any desired target glass tran-sition temperature by incorporating plasticizers (reduce Tg) or high molecular weightpolymers (increase Tg).
It should be cautioned, however, that although glass transition (and thereforemicrocapsule stability) is clearly related to the material properties of the matrix andrates of crystallization, there is growing evidence that in the glass transition region,small molecules are more mobile than might be expected from the high viscosityof the matrix (Parker and Ring, 1995). The mechanism of degradation of molecules
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