Encapsulation and Controlled ReleaseTechnologies in Food Systems

Encapsulation andControlled ReleaseTechnologies in FoodSystemsEDITED BY

Jamileh M. LakkisExpert in encapsulation and controlled release technologiesBarcelonaSpain

SECOND EDITION

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1 2016

To my family

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