Sagalowicz & Leser 2010_Delivery Systems for Liquid Food Products

Current Opinion in Colloid & Interface Science 15 (2010) 61–72

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Current Opinion in Colloid & Interface Science

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Delivery systems for liquid food products

Laurent Sagalowicz ⁎, Martin E. LeserNestlé Research Center, Vers-Chez-Les-Blanc, CH-1000 Lausanne 26, Switzerland

⁎ Corresponding author.E-mail addresses: [email protected]

[email protected] (M.E. Leser).

1359-0294/$ – see front matter © 2009 Published by Edoi:10.1016/j.cocis.2009.12.003

a b s t r a c t
a r t i c l e i n f o
Article history:Received 2 December 2009Accepted 7 December 2009Available online 13 December 2009

Keywords:Delivery systemsEmulsionsParticlesSurfactant self-assemblyNutrientsFortification

One of the present challenges of the food industry is to deliver nutrition and health benefits to the consumerwhile keeping, or improving the taste and aroma impact. Adding active ingredients to liquid food productsfor fortification is in most cases not possible or not sufficient to achieve the desired goal, due to the fact thatmany interesting micronutrients are only hardly soluble in aqueous systems and show (i) a limited stabilityagainst chemical or physical degradation, (ii) an incompatibility between the active ingredient and the foodmatrix, or (iii) reveal an uncontrolled release or bioavailability. Therefore, encapsulation systems, alsodenoted as ‘delivery systems’, are typically used to solve these formulation problems. The task to find theappropriate delivery system is especially challenging for the food industry compared to other fields such aspharmacy, medical products or cosmetics, since only a limited amount of ingredients can be used asencapsulation and stabilization material. In the present review we will discuss the delivery systems availablefor (semi)-liquid foods and comment on existing advantages and limitations. The remaining technicalchallenges to solve in the future concern mainly the facts that (i) most of the available delivery systems foraqueous products do not yet allow to significantly stabilize degradation sensitive ‘encapsulated’ activeingredients against e.g. oxidation, (ii) the ‘encapsulation’ (solubilization) capacity of some delivery systemsis still quite poor and (iii) off-taste generation is possible above certain concentrations of added deliverysystems.

m (L. Sagalowicz),

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© 2009 Published by Elsevier Ltd.

1. Introduction

Consumers in the industrialised world are becoming increasinglyaware of the relationship between diet and health. Thus, the demandfor a balanced diet and functional food products that address specifichealth benefits is growing steadily. Healthy food products, ascompared to their standard counterparts, can be characterised byseveral attributes: containing (i) low to moderate sodium, sugar andtrans-fat content, (ii) significantly reduced energy density (iii) anincreasing amount of whole grain and dietary fibre, (iv) high quantityof milk and vegetable proteins, or (v) bioactive ingredients, i.e.,nutrients which have health sustaining properties [1]. However, manyof the nutritionally attractive micronutrients used for fortificationcannot just be added to the product, since they are either only hardlysoluble in aqueous systems, show a limited stability against chemicalor physical degradation, or reveal an uncontrolled release or bio-availability. Moreover, the stability, bioavailability or bioefficacy ofactive substances strongly depend on the food matrix and the chosen(micro)encapsulation or delivery system [2–5].

Spray-drying (micro)encapsulation has been used in the foodindustry since the late 1950s to provide, especially for flavour oilssome protection against degradation/oxidation, and to convert liquids

to powders [6]. Microencapsulation is defined as a process in whichtiny particles or droplets of the active ingredient(s) are surrounded bya coating, or embedded in a homogeneous or heterogeneous matrix,to give small capsules with many useful properties. Microencapsula-tion can also provide a physical barrier between different activeingredients in the solid product [7]. For example, iron can be isolatedfrom vitamin A. One of the principal goals of microencapsulationnowadays is to protect the active ingredients from both chemical (e.g.oxidation) or physical (e.g. precipitation, crystallisation) degradationinduced through exposure to oxygen, light, moisture, temperature orionic strength changes or to allow controlled or sustained release ofactive ingredients under desired conditions, i.e., during eating ordigestion. Due to the low diffusion coefficient of oxygen in the glassycapsule material and due to the relatively large particle size (usuallylarger than 200 μm), sensitive oils, such as flavours and essential oilscan be stabilized up to several years [8]. Such an impressive deliveryperformance creates still today an enormous interest by foodtechnologists in using microencapsulation based on spray drying,freeze drying, fluid bed coating or extrusion [6,9]. In its simplest form,a solid microcapsule is a small sphere with a uniform wall around it.Thematerial inside themicrocapsule is referred to as the core, internalphase, or fill, whereas the wall is sometimes called shell, coating, wallmaterial, or membrane [10]. The microcapsule may even havemultiple walls. The choice of the wall material is very important forencapsulation efficiency and microcapsule stability. The criteria forselecting a suitable wall material are mainly based on its physico-

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62 L. Sagalowicz, M.E. Leser / Current Opinion in Colloid & Interface Science 15 (2010) 61–72

chemical properties such as solubility, molecular weight, glass/melting transition, crystallinity, diffusibility, film forming and emul-sifying properties or costs. Most used wall materials are biopolymersof various sources, such as natural gums (gum Arabic, alginates,carrageenans, etc.), proteins (milk or whey proteins, soy proteins,gelatin, etc.), starches, maltodextrins with different dextrose equiva-lents, corn syrup, waxes and their derivatives [10].

Fortification of liquid products, such as drinks, juices, etc, is gettingmore and more fashionable in foods. In this case the (micro)encapsulated active ingredients must be stabilized in a liquidenvironment, which is considerably different from stabilizing theactive ingredients in a solid environment. Since almost all spray-drying processes in the food industry are carried out from aqueousfeed formulations, the used wall material must be soluble in water atan acceptable level [6]. Solid microcapsules or powders cannot besimply added to an aqueous food product without losing the barrierand stabilization function of the solid capsule shell material. Whenadding the solid microcapsules into water, the capsule shell or matrixmaterial is basically dissolved into the aqueous phase releasing theactive ingredients into the liquid phase and, in general, protectionagainst degradation is lost. Therefore, delivering active ingredients ina liquid matrix requires the use of different encapsulation and pro-tection strategies.

Obviously, the delivery of active ingredients in a fluid aqueous phaseis by farmore challenging than the delivery of the active ingredients in asolidphase.Moreover, for liquids, appropriate encapsulation techniquesdepend critically also on the solubility characteristics of the activeingredients. For hydrophilic components, the suitable delivery strate-gies and ‘capsules’ of choice differ verymuch from the approach to takefor the delivery of lipophilic micronutrients.

The list of micronutrients and bioactive substances, which areinteresting to be added to food products is quite wide. Also theirphysico-chemical properties are very different. Most of them areextracted from plants, fungi, micro algae or marine biomass.Polyphenols, a class of dietary antioxidants, (primarily consisting offlavonoids such as catechins, flavones, isoflavones, flavonols, flavo-nones and anthocyanins) capture free radicals, prevent lipids fromoxidation and often exhibit antimicrobial and antiviral properties[11,12]. They, therefore, protect human cells and help reducing therisk of chronic diseases. Carotenoids, another class of importantantioxidants, (e.g. lycopene, luteine, zeaxanthin, astaxanthin and β-carotene) also protect human cells from oxidative stress [13].Essential poly-unsaturated fatty acids and their derivatives (e.g.docosahexaenoic acid, arachidonic acid) are another class of impor-tant nutrients, since they are required for the development of thehuman brain and play an important role in immunity [14]. Last but notleast, various amino acids, peptides (e.g. glyco-macro peptides frommilk) or proteins, vitamins, (CADEK), phytochemicals (e.g. phytoster-ols), minerals (calcium, magnesium, iron, zinc, selenium, chromium),and probiotic bacteria, are often added to food products to induce arange of different health-promoting and sustaining effects [15].

The successful development of bioactive containing deliverysystems for liquid products depends on several factors: (i) the abilityto disperse active ingredients into an aqueous phase, in case theactives are water insoluble, (ii) the stability of the ‘capsule’ structure,preventing effects like creaming or sedimentation, (iii) minimisingthe impact on the textural, rheological or optical properties of the finalfood product, (iv) protection of the encapsulated active moleculesagainst degradation during processing and storage, and (v) controlledrelease during consumption, either in the mouth or during digestionin the GI tract. Most challenging in practical applications seems to bethe sufficient stabilization of oxidation sensitive active molecules,such as vitamins or polyphenols. Moreover, masking possible off-tasteeffects or increasing (or controlling) the bioavailability or bioefficacyof the active ingredients during digestion are also quite demandingtasks to achieve in practical situations.

In this review, we will describe the different types of deliverysystemswhich can be used for the fortification of liquid food products,and their interactions with the active molecules. We will mention thefunctionalities focussing on advantages and limitations of the availabledelivery systems. Finally, we will discuss some remaining challengesand speculate on what kind of research will be necessary in the futureto develop further the science area of liquid delivery systems.

2. Systems available for the delivery in liquid food products

In general, a wide selection of delivery systems is available for theuse in food systems. Ultimately, one would like to relate thecharacteristics of the delivery systems to the functional attributes ofthe final product, such as sensory, physico-chemical and biological/nutritional impact [15,16]. Fig. 1 summarizes the various types ofsystems which can be used for the delivery of active ingredients inaqueous liquid products. Although solid microcapsules represent thelarge majorities of delivery systems used in food, since the availableshell materials is very powerful in, for instance, protecting oxidationsensitive active ingredients from the contact with oxygen or heavymetals in powders, they are much less attractive for the delivery inaqueous systems, as mentioned above. Therefore, there is anincreasing need to adapt the capsule material to liquid basedproducts, i.e., the use of lipophilic materials, such as waxes or fats.An example are the solid-lipid (nano)particles. Other deliverystrategies are exploiting the idea to build around ordinary emulsionoil droplets a multilayer structure, e.g. ‘shell’ that is able to preventcontact of the encapsulated oily active ingredient with the aqueouscontinuous phase. The main activity in the research field of aqueousdelivery systems is, however, to try to physically or chemically‘complex’ or ‘bind’ the active ingredient to a molecular or supramo-lecular structure with the hope to protect it in this way from chemicalor physical deterioration. Examples of such delivery systems arecyclodextrin complexes, complexes with milk proteins, such as Nacaseinate or whey proteins or their adequate aggregates, protein–polysaccharide complexes, also denoted as coacervates, or complexformation with polysaccharides, like amylose. Self-assembly structureformation is also used for solubilizing (lipophilic) active ingredientsinto aqueous products. Prominent self-assembly delivery systems aremicelles, microemulsions, liposomes or liquid crystalline particles,such as cubosomes, hexosomes and others.

In this review, wewill mainly focus on delivery systems that have adiameter less than about 1–2 μm. Such colloidal systems aremuch lesssusceptible to creaming or sedimentation in the final fortified liquidproduct. Therefore, we will exclude delivery concepts, which are onlyable to produce supra-micron particles. In order to avoid creaming/sedimentation in the latter systems, the aqueous continuous phasehas to be viscous or gellified or density matching components have tobe added.

3. Oil-in-water emulsions

Lipophilic active ingredients can be delivered in different forms.The best described and researched ‘encapsulation system’ for lipidicmaterials in aqueous products are oil-in-water emulsions. Emulsions,such as, milk, yogurt drinks, dressings, sauces or mayonnaise, areubiquitous in food. Their oil droplets can easily be used for thedelivery of lipophilic active ingredients. For example, the delivery ofthe antioxidant vitamin E (tocopherol) is very important in food.Vitamin E is the major and most potent lipid-soluble antioxidant invivo [17]. It functions as the major radical scavenging antioxidant inlipoproteins and efficiently interrupts the chain propagation of lipidoxidation, thus protecting poly-unsaturated fatty acids and low-density lipoproteins from oxidation. Vitamin E or its derivativesare frequently added to the oil phase of o/w emulsion products forfortification reasons or in order to stabilize unsaturated oils against

Fig. 1. Description of various kinds of delivery systems for liquid products. Advantages and limitations are briefly summarized. The right column represents electron microscopyimages of the various delivery systems. For the solid particles: SEM image of spray-dried particles, courtesy, J. Ubbink. For the emulsion: Cryo-TEM image of an oil droplet. For thecomplexes: freeze-fracture TEM image of a casein micelle. For the liposomes: Cryo-TEM of a unilamellar vesicle. For the microemulsions: Cryo-TEM image of a Tween 80 micellarsolution. For the dispersed reversed surfactant systems: Cryo-TEM image of a particle having the internal structure of a reversed micellar cubic phase (space group Fd-3m).

63L. Sagalowicz, M.E. Leser / Current Opinion in Colloid & Interface Science 15 (2010) 61–72

Fig. 2. Schematic of a multilayered emulsion droplet stabilized by an emulsifier (e.g.lecithin) and a polymer (e.g. chitosan). The large thickness of the interfacial layer aswell as the positive net chargemay be responsible for themeasured increase in stabilityof the oil molecules against oxidation.Courtesy D. J. McClements.


oxidation [18,19]. Since vitamin E acetate is chemically more stablethan vitamin E itself, it is especially used in food technology forfortification reasons.

For many nutrients, however, a classical emulsion delivery systemdoes not offer the desired properties in terms of solubilization (e.g.preventing crystallisation), protection against chemical degradation orinducing the desirednutritional activity. For example, classical emulsionsystems donot protect unsaturated triglycerides, essential oils, vitaminsA and D efficiently against degradation. Therefore other ideas areneeded todeliver such ingredientswithout losing their nutritional effectduring shelf-life of the product. Oneway to achieve this is by controllingthe composition and structure of the oil droplet interface, i.e., bybuilding around the oil droplets multilayers of polymers or surfactants.

3.1. Multilayer emulsions

McClements and co-workers showed that when stabilizing oildroplets first with an anionic surfactant, such as a phospholipid, andthen adding a positively charged polymer, such as chitosan to theemulsion, thedroplets are coatedwith a surfactant-polymermembrane,whichgives theglobules apositive charge [20–22] asdepicted in Fig. 2. Itwas observed that this kind of emulsion protects more efficiently Ω 3fatty acids and essential oils (citral and limonene) from oxidation thatordinary emulsions stabilized by a single surfactant or amphiphilic layer[20–22]. The observed effect against oxidation of the oil droplets in thismultilayer emulsion systemwas attributed to the net positively chargedinterface. A positive charge around oil droplets hinders the contact withtransitionmetals, like iron or zinc, and as a consequence, prevents themto act as a pro-oxidant of the oil droplets. Note that lipid oxidation isknown to be strongly catalyzed by transition metals, and preventingthem to be in contact with sensitive oils can drastically increase thestability against oxidation. The relatively large thickness of the interfacemay also have a positive influence in terms of a barrier function. Inconclusion, an efficient control of the water–oil droplet interfacereduces oxidation of sensitive oil droplets, like poly-unsaturated fattyacids (PUFA) [22], or essential oils suchas citral and limonene [21]whencompared to normally stabilized oil droplets.

3.2. Double emulsions

Double emulsions, also often denoted as ‘multiple emulsions’, are“emulsions of an emulsion”, e.g. a water-in-oil emulsion dispersed in anaqueous phase (water-in-oil-in-water, W/O/W). Such emulsions areinteresting as delivery systems, since, in principle, the water dropletsinside the oil droplets can be used to deliver (unstable) hydrophilicactive ingredients separating them from the outer aqueous phase of the

food product. Therefore, most studied applications of double emulsionsare related to the control of the release of hydrophilic substances fromthe inner to the outer aqueous phase [23]. Themain problemswith foodrelated applications of double emulsions are to find the suitable food-grade emulsifiers and stabilizers for the inner and outer emulsion (toavoid ‘mixing’ of the two type of emulsifiers), and to prepare suchemulsions in a form that they exhibit an acceptable shelf-life stabilityand desired controlled release behaviour.

Recently, Benichou et al. [24] studied the double emulsionstabilization potential of WPI (Whey Protein Isolate)/polysaccharide(e.g. xanthan gum) complexes in comparison to each of thebiopolymers alone. A synergistic positive effect with regard to thedouble emulsion stability was demonstrated, which was associated tomodified surface properties induced by the adsorption of thecomplexes. The authors also showed that these double emulsionscan be used for entrapping hydrophilic vitamins, such as vitamin B1,into the inner aqueous phase. By means of Differential PulsePolarography it was possible to follow the real-time release of theentrapped vitamins from the core of the W/O/W double emulsiondroplets to the outer aqueous phase. A similar study using biopolymer-conjugates was published recently by Fechner et al. [25]. Anotherchallenge is to entrap lactic acid bacteria into the inner water phase ofdouble emulsions. Pimentel-González et al. [26] reported on doubleemulsion ‘encapsulated’ Lactobacillus rhamnosus cultured in sweetwhey and harvested in the late log phase. The primary and doubleemulsion droplets showed practically no changes in their morphologyand droplet size with aging time. The viability of the entrapped L.rhamnosus in the double emulsion was compared to that of non-entrapped control cells exposed to low pH and bile salt conditions.While the viability of the control cells decreased significantly underlow pH and bile salt conditions respectively, the survival of theentrapped cells increased significantly under low pH and bile saltconditions. It was concluded that the double emulsion protected L.rhamnosus against simulated gastrointestinal tract conditions. This is aquite remarkable result. However, the successful use of doubleemulsions for the delivery of hydrophilic active ingredients is stillcritically depending on the progress we will make in the future incontrolling the manufacture of such emulsions. Traditional fabricationby means of two subsequent emulsification steps leads to very ill-controlled structuring. Therefore, new approaches to control the quitecomplex structure of double emulsions are needed. For instance, Utadaet al. [27] showed that by using a microcapillary (i.e., microfluidics)device, it is possible to fabricate double emulsions that contained asingle internal droplet in a very well defined geometry, e.g., a core-shell geometry. The authors showed that the droplet size can bequantitatively predicted from the flow profiles of the fluids, andencapsulation structures can be generated by manipulating theproperties of the fluid that makes up the shell. The high degree ofcontrol afforded by this method and the completely separate fluidstreams make this a flexible and promising technique. Hanson et al.[28] showed, recently, that water-in-oil-in-water double emulsionscan be prepared in a simple process (i.e., not in two steps, as usually isdone) and stabilized over many months using single-component,synthetic amphiphilic diblock copolypeptide surfactants. The pro-duced double emulsions were even stable against extreme flow,leading to directmass productionof robust double nanoemulsions thatare amenable to nanostructured encapsulation applications in foods,cosmetics and drug delivery. Use of block copolypeptide surfactantsovercomes key limitations of W/O/W double emulsions by allowingthe straightforward preparation of stable nanoscale droplets that cansimultaneously encapsulate both oil-soluble andwater-soluble cargos.

3.3. Nanoemulsions

Nanoemulsions, often also called miniemulsions, are emulsionsconsisting of droplets which are significantly (by a factor of 10 or so)


smaller than the droplets present in ordinary emulsions [29]. Asemulsions, they are thermodynamically unstable systems exhibiting,however, high kinetic stability which can be for several years [29].Moreover their lowviscosity and optical transparencymake themveryattractive delivery systems for example, in the pharmaceutical field asdrug delivery or other application area [30]. A direct consequence ofthe thermodynamic instability of nanoemulsions is that theirformation requires external energy. There are two main preparationmethods available [31,32]; the so called dispersion or high-energymethods, that consist of the application of high mechanical energyduring emulsification, and the condensation or low-energy ones, inwhich a change of curvature and a phase transition takes place duringthe emulsification process. In condensation methods temperature(Emulsion Inversion Point method, EIP) or the composition (PhaseInversion Temperaturemethod, PIT) ismaintained constant. However,the preparation of nanoemulsions stabilized with ionic surfactants bycondensation methods is not feasible, since the PIT method cannot beused, as temperature does not change the behaviour of ionicsurfactants. The required change of curvature could be obtained inthis case by varying the degree of ionization of the surfactant [31].

The very small droplet size of nanoemulsions (20–200 nm) makesthem resistant to physical destabilization via gravitational separation,flocculation and/or coalescence [33]. Nanoemulsions are resistant tocreaming because their Brownianmotion is enough to overcome theirlow gravitational separation force. They are also resistant toflocculation because of highly efficient steric stabilization. Mostnanoemulsions are stabilized by synthetic surfactants which tend tohave long hydrophilic tails of the order of 2–10 nm. The high ratio ofsteric layer thickness to droplet diameter (δ/r ratio) means that stericstabilization is very effective and even weak flocculation is prevented.However, nanoemulsions are particularly prone to a growth inparticle size over time by a process known as Ostwald ripening [33].Ostwald ripening is a process whereby the larger droplets in anemulsion grow at the expense of the smaller droplets because ofmolecular diffusion of oil between droplets through the continuousphase. This process is driven by the Kelvin effect where the smallemulsion droplets have higher local oil solubility than the largerdroplets because of the difference in Laplace pressure. The rate ofOstwald ripening is largely dictated by the solubility of the oil in thecontinuous phase C(∞) [33].The aqueous phase solubility of an oildecreases linearly with oil molar volume, Vm. Therefore, low molarvolume oils (200–350 cm3 mol−1) show an appreciable solubility inwater resulting in destabilization by Ostwald ripening. On theother hand, the large molar volume of long chain triglyceride oils(∼900 cm3 mol−1) should make them insoluble in water thuspreventing Ostwald ripening. Note that the formation of truetriglyceride oil nanoemulsions appears, however, difficult mainlybecause of the relative high viscosity of the triglyceride oil.

In order to slow down Ostwald ripening in oil-in-water nanoe-mulsions, in which the oil is relatively soluble in thewater phase, suchas essential oils, a second oil with much lower continuous phasesolubility, such as high molecular weight triglyceride oils, can beadded to the smaller molecule oil phase [33]. This concept is alreadyknown for years and is based on the premise that the entropy ofmixing provides a chemical potential that opposes Ostwald ripening.When a mixed oil nanoemulsion undergoes Ostwald ripening, thesoluble oil has greater mobility between droplets. Over time, largerdroplets become enriched with the soluble oil and smaller dropletsbecome enriched with the insoluble oil. This creates a compositionalimbalance that is of higher entropy than a perfectly mixed system.

An advantage of using nanoemulsion instead of ordinary emulsiondelivery systems lies in the fact that the bioavailability and bioefficacyof the delivered lipophilic bioactives can be expected to be greaterwhen delivered in form of a nanoemulsion instead of a normalemulsion. Recently, Wang et al. [34] described the anti-inflammationactivity of curcumin when delivered through o/w nanoemulsions

stabilized by Tween 20. The authors could show that 80 nmnanoemulsion droplets exhibit higher anti-inflammation activitythan emulsions containing 620 nm sized emulsion droplets. Interest-ingly enough, when delivering the curcumin in a micellar Tween 20solution the biological activity (inhibition on the edema of mouse ear)is significantly lower than when delivering the active ingredient inform of an emulsion or nanoemulsion. Although the measured effectsare quite striking, the exact structure–function relation in this systemis by far not clarified. Recently, Wulff-Pérez et al. [35] studiednanoemulsions from natural oils like soybean, olive and sesame oilthat can be used to deliver lipophilic bioactives in parenteralnanoemulsions produced by means of ultrasound homogenisation.As emulsifier the non-toxic triblock ABA-type copolymer surfactantPluronic F68 was used. At relatively low surfactant concentrationsthe emulsions proved to be stable against Ostwald ripening andcoalescence, even in the presence of relatively high oil dropletvolume fractions (0.25). At higher polymer concentrations, however,a reversible flocculation destabilization (depletion flocculation) wasobserved showing the subtle effect of other structures, present in theproduct, on the physical properties of the nanodroplets. Yuang et al.[36] investigated oil-in-water nanoemulsions of β-carotene producedby high pressure homogenization. While the physical stability of thenanoemulsions, which were stabilized by polysorbate emulsifiers,was quite acceptable, significant chemical degradation of thedelivered β-carotene occurred during storage. This study clearlyshows that although nanoemulsions can be formulated also for foodapplications in a (relatively) stable form, the main remainingchallenge is to achieve also an acceptable bioactive stability againstchemical degradation during processing and storage of the fortifiedproduct.

4. Solid lipid nanoparticles

Solid lipid nanoparticles carriers (SLNs) have some similarities withnanoemulsion systems. The diameter of such lipid particles can be alsoquite small, i.e. in the range between 50 nm and 1 µm. The maindifference is, however, that the SLNs consist of a solid or semi-solidlipidic core containing lipophilic active ingredients. Active ingredientscan be solubilizedhomogeneously either in the core of the SLNs or in theoutside part [37]. The advantage of SLNs as delivery system for lipophilicactive components is reported to lie in the immobilisation of activeelements by the solid particle structure leading to an increased chemicalprotection, less leakage and sustained release [38,39]. This physicalproperty allows a better control of both the physical (against re-crystallisation) and chemical (against degradation) stability of thedelivered nutrients. The preparation of SLNs is achieved by heating thelipidic core components above their melting point, and then usingcommon emulsion or microemulsion technology, i.e., homogenisationor mixing of the melted lipidic phase with a cold aqueous solutiongenerating re-crystallised lipidicparticles. Themaindifficulty associatedwith SLNs production is to control the lipid polymorphism. Triglycer-ides, for example, can be present in three different crystalline structuresα,β′, andβ. Bunjes et al. [40] showed thedifferent crystal structures andmorphologies these particles can have using a combination of X-raydiffraction, Cryo-transmission electron microscopy (plunging tech-nique) and freeze-fracture electron microscopy. While the α structuregives a shape close to a sphere, the β structure adopts a needle or plate-like shape with much less defects. This suggests that only the α form issuitable as delivery system since the structure is relatively defectivewhile the crystals of the β′ and β structures are much more perfect intheir crystal structure ejecting the ‘encapsulated’ active elements to theoutside of the particle. In addition, the plate-like crystals of the β formhave a tendency to growmuchmore leading todestabilizationand togelformation. Therefore, it is of prime importance to control particlecrystalline structure, i.e., preferably being in the α lattice.

Fig. 3. Schematic representation of the structure of the cyclodextrin (β form in thedrawing) molecule and the mechanism of drug (nutrient or aroma) complexation. (a)Cyclodextrin structure view from different angles. (b) Complexation with a drugmolecule.Adapted from Davis and Brewster [46].


Formation of a certain crystal structure depends on many factors,such as lipid composition, cooling rate and present crystal habitmodifiers, as surfactants. High cooling rates favours the presence ofthe less stable α form, while low cooling rates favours the presence ofmore stable β crystals [38]. Surfactants may stabilize a given crystalform. It was recently found that a blend of saturated long chainphospholipids and bile salts stabilize the α form [41].

Concerning the effect on the encapsulated active ingredients, there isevidence that SLN particles can protect sensitive bioactives fromdegradation such as hydrolysis or oxidation [39]. Vitamin A is sensitiveto degradation by oxidation and polymerisation,which are catalyzed bylight and transitionmetals [2]. Carlotti et al. [42] found that between 50and 70% of retinol remains undegraded when ‘encapsulated’ in SLNsmade of Cetyl palmitate (30% of vitamin A was degraded), Glycerylbehenate (49% degradation) and palmitic acid (34% degradation),while8% retinol remains when delivered in standard oil-in-water emulsions.An important application of SLNs is in thefield of controlled drug release[39]. Yang et al. [43] showed that camptothecin, which is an anti-tumoragent can be released for up to oneweekwhen solubilized into SLNs. It issupposed that when nutrients are solubilized in the inner core of SLNs,there will be sustained release, while solubilization in the outside shellor in the solid solution will give rise to a burst release [39].

SLNs can also control the penetration of several actives into theskin, which makes them attractive for cosmetic applications andtopical delivery [44].

In conclusion, SLNs seem to have a large potential for the protectionof active components, but the lack of physical stability (e.g. transfor-mation of the α crystal into β or β′ resulting in particle growth andejection of loaded active molecules), is at present the major issue whentrying to apply them as a delivery system for food. In addition, activeelements may be exposed to high temperatures during the preparationof the lipid carrier material leading to chemical degradation. Finally,saturated lipids are needed to obtain these kinds of delivery system.Such lipids are not the preferred ones in terms of nutrition and health.

5. Molecular complexes

Another strategy to deliver active ingredients in aqueous foods isby physically complexing them with other molecules, hoping that inthis way a better solubilization and/or an increase in the chemicalstability of the complexed bioactive can be achieved. In this context amolecular complex is referring to the physical association between ahost and a guest (active ingredient) molecule. The most studied hostmolecules are the cyclodextrins. However, molecular association withother polysaccharides (e.g. amylose) or proteins or their aggregatescan also be achieved.

5.1. Cyclodextrins

Cyclodextrins (also abbreviated as CD) are cyclic (or taurus shape)oligosaccharides having a hydrophilic outer surface insuring gooddissolution of the complex in an aqueous environment (Fig. 3a).Cyclodextrins contain a lipophilic cavity enabling to host relativelysmall lipophilic or amphiphilic constituents (Fig. 3b), such as fatty acids,vegetable and essential oils, nucleic acids, vitamins and hormones[45,46]. There are three main types of cyclodextrins: (i) α, cor-responding to 6 glucopyranose units linked by α-(1,4) bonds, (ii) β,corresponding to 7 units (U) and (iii) γ, corresponding to 8 U. Thedimensions of the internal cavity are crucial for the ‘encapsulation’ ofguestmolecules. Onlymolecules, whichfit physically into the cavity canbe incorporated. The cavity diameter varies between 0.5 and 0.8 nmwhich is relatively small allowing the solubilization of only relativelysmall molecules. Long guest molecules may not be protected in anoptimal way due to the limited height of the taurus [46].

Since 2008,α-cyclodextrin is recognised as a novel food ingredient.While the β-form is authorized in all countries, the γ-form can only be

used in certain countries; it is, for instance not authorized in Europe(yet). The large majority of published applications of cyclodextrinsare in the field of pharmaceutics. Interest comes from the fact thatcyclodextrins considerably help molecular solubilization and thuscan increase biodisponibility, bioavailability and bioefficacy [47].In addition, drugs can be protected against photodegradation andhydrolysis when solubilized into cyclodextrin [47]. Concerning foodapplications, CD can be used for flavour protection or flavour deliveryand to reduce bitterness and bad smell and taste [48]. In food, themost used application concerns the removal of cholesterol in animalproducts such as eggs [48,49]. Lin et al. [50] and Mumoz-Botella et al.[51] showed that cyclodextrins protect retinoids (vitamin A) fromphotodegradation. After 60 min of exposure to light, 44.3% of all-transretinoic acid remains when solubilized in cyclodextrin while 31.8%remains intact when present in ethanol.

The main limitation of using cyclodextrins is related to theirmoderate and limited loading capacity since there is always anequilibrium between the amount of molecule solubilized in thecyclodextrin cavity and outside [46]. Loading of eugenol, inside β-CD,was found to be 90% while it was 100% when using an emulsiondiffusion method with polycaprolactone [52].

The loading capacity of a delivery vehicle, i.e., the molar ratiobetween the encapsulated and encapsulating material is a veryimportant property characterising the encapsulation efficiency of adelivery system. Choi et al. [53] observed by means of transmissionelectron microscopy aggregation between fish oil and β-CD. In thepresence of 10 times more β-CD than fish oil, hexagonal-typeaggregates having a diameter of 300 nm, are observed. It seems thatthe cyclodextrin is at the outside of these aggregates, and most of thefish oil is in the inside of the CD particle structure. In the presence of aratio of 1:1 between fish oil and β-CD, other types of supramolecularaggregates are formed. Their diameter is in the range of 600 nm. Thisstudy indicates that CDs cannot only complex molecules in theircavity in a molecular form, but that cyclodextrin molecules can alsoform a sort of self-assembly structure, which is able to ‘encapsulate’especially largemolecules like triglycerides. In addition, the process tosolubilize guest molecules in cyclodextrins is relatively complex andfull equilibrium solubilization is obtained only after one week [48].


5.2. Molecular association with biopolymers

Active molecules can form physical complexes also with a varietyof other naturally occurring food components. Such systems are thebase for designing ‘natural’ delivery systems. An example is amylosepresent in starch, which can adopt a helical structure generating acavity of about 0.5 nm in diameter. Small molecules like aromas canbe solubilized in this cavity. It is known already for a little while thatstarch granules, which contain amylose, can strongly influence aromarelease [54]. Amylose complexes can from either an amorphous orcrystalline structure. Slight hydroxypropylation of starch provides aroute for obtaining soluble complexes which do not aggregate [54].Although amylose has some similarities to cyclodextrins, it is muchless used and studied as a delivery system for aqueous systems.

Proteins and peptides are amphiphilic molecules. They are alsorelatively soluble inwater and canbind lipophilic or amphiphilic activeingredients. Semo et al. [55] used casein micelles to solubilize vitaminD2. Sodiumcaseinate, CaCl2 andK2HPO4were used to encapsulate thevitamin and reconstitute the casein micelle solution. It was found thatthe casein micelle can provide a partial protection against UV-light-induced degradation compared to the serum media (of the caseinmicelle dispersion), which was used as a control [55]. Zimet et al. [56]used β-lactoglobulin and β-lactoglobulin complexed with pectin asdelivery system for Ω 3 PUFA. Optimum β-lactoglobulin complexeshad a diameter of about 100 nm and were claimed to protect PUFAduring a stress test at 40 °C at pH=7.More precisely, it was found thatthe various samples tested could be ranked in order of increasingprotective effects as follows: DHA in water<DHA in β-lactoglobu-lin<DHA in β-lactoglobulin–pectin complex. A more detailed reviewon the use of milk proteins as vehicles for bioactives is published by Y.Livney in the same section of this journal [57].

6. Self-assembly delivery systems

Self-assembly structures, such as micelles, microemulsions, andliquid crystalline phases, are formed by the spontaneous associationof surfactants in aqueous (or oil) phases. Surfactants are used in manyfood applications, such as in bread and cake production for theimprovement of shelf-life (prevention of starch retrogradation due toformation of monoglyceride–amylose complexes) and flavour reten-tion [58]. Another important application of surfactants deals with thecontrol of emulsion or foam formation and stabilization. All theseapplications are based on the potential of amphiphiles to adsorb atinterfaces or to crystallise and co-crystallise with other molecules.

An intriguing characteristic of amphiphiles is their capacity to formvarious self-assembly structures when added into water. For food, thisproperty is mainly seen with polar lipids, such as monoglycerides andphospholipids [59–62]. Amphiphiles are molecules containing alipophilic part and an amphiphilic part. If mixed with water, thelipophilic hydrocarbon part of the molecule will be shielded from thewater molecules by the formation of self-assembly structures.Therefore, the self-assembly process is spontaneous, meaning thatno energy (homogenisation) is required to form the structure.However, in reality the situation is not so simple since manysurfactants in food are at least partly crystalline at room temperatureforming some sort of crystals. Thus, only at temperatures, higher thantheir melting temperature (Krafft temperature) self-assembly struc-ture formation is induced.

One of the most useful (and simple) concept, for a semi-quantitative description of the relation between surfactant molecularshape and self-assembly phase formation, was given by Israelachviliet al. [63] and Tanford [64] who defined the so-called dimensionlesssurfactant packing parameter P.

P = V = al

where V is the molecular volume of the hydrophobic moiety, l themolecular length of the hydrocarbon chain and a is the effective (orhydrated) cross-sectional area of the polar head-group. Depending onP, different self-assembly structures can be formed (see Fig. 4). If P issmall (P≪1), structures like normal micelles, hexagonal (Hi) or cubicphases are formed. If P is close to 1, a lamellar liquid crystalline (Lα)phase is formed, which when dispersed into water gives rise tovesicles or liposomes formation. If P is large (P≫1), reversed self-assembly structures, such as reversed micelles, reversed hexagonal(Hii) or reversed cubic structures are formed.

In the following we describe the use of self-assembly structuresin the delivery of active ingredients in aqueous media, focussing on(i) micelles (or microemulsions), (ii) liposomes and (iii) dispersedreversed self-assembly structures. The advantage of using surfactantself-assembly structures is that the compartmentalisation degreeof the structures is very high, i.e., the characteristic solubilizationdomains are very small (in the order of 10 nm). As a consequence, thecreated interface between the aqueous and lipidic domain isextremely large. Ericson et al. [65] reported that, for instance, thereversed gyroid bicontinuous cubic phase forms a surface area of400 m2 g−1 phase. The presence of this tremendous amount ofinterface allows to create new delivery functionalities, which arebasically linked to the possibility to preferentially solubilize amphi-philic active ingredients into such structures. This offers newopportunities to control chemical reactions such as oxidation orMaillard reaction in such systems [66–68].

6.1. Micelles and microemulsions

Oil-in-water microemulsions (also called ‘filled’ micelles; filledwith lipophilic guest molecules), unlike o/w nanoemulsions, arethermodynamically stable and are formed spontaneously. Althoughboth systems show long-term stability (due to a different mechanism,however) microemulsions are much more sensitive to environmentalchanges, such as temperature, ionic strength, composition (adding/removing molecules to/from the aqueous continuous phase). Adrawback when comparing to nanoemulsions, is that microemulsionformation requires the use of relatively large amounts of surfactant,i.e., their loading capacity is significantly lower than this of comparablenanoemulsion delivery systems, especiallywhen using triglycerides asthe dispersed oil phase.Moreover,making food-grademicroemulsionsis still quite challenging because of the limited choice of suitable food-grade emulsifiers. The best investigated class of food surfactants formicroemulsion formation is the polysorbates (Tweens) [59].

In spite of the above mentioned limits, the use of o/w microemul-sions for the delivery of active ingredients is a widely investigatedresearch field [69–71] both for pharmaceutical and food applications.In this chapter we will concentrate mainly on new developments inthis field.

In the past, the research group of N. Garti showed in variouspublications the excellent solubilization effect of microemulsionsystems for lipophilic nutrients, such as β-carotene, lycopene, luteinor phytosterol [70,71]. However, the question concerning the nutrientchemical stability in such microemulsion delivery systems over timewas investigated in a much lesser extent, and we do not know yetwhether o/wmicroemulsion systems principally stabilize or destabilizesolubilized lipophilic molecules against degradation. This is, as anexample, the case for the chemical stability of lycopene or β-carotene ino/wmicroemulsions asmentioned by Loveday and Singh [2]. Garti et al.[72] reported that on exposure to sunlight, lycopene degrades moreslowly in o/w microemulsions than in an organic solvent. However,Szymula [73] showed that β-carotene degradation in sunlight wasfastest in o/w microemulsions, followed by water-in-oil (w/o) micro-emulsions and pure pentanol. The authors suggest that the highconcentrationofβ-carotene in theoil droplets of theo/wmicroemulsionpromotes degradation. A certain delivery system may have some

Fig. 4. Summarizes the different existing surfactant self-assembly structures as function of their Packing parameter P. Going from top to bottom, corresponds to an increase in thePacking parameter; inspired by Jönsson, et al. [96]. (b) Cryo-TEM image of a particle having an internal reversed hexagonal phase. Reprinted with permission from Yaghmur et al.[85]. Copyright (2005) American Chemical Society; (c) Cryo-TEM from a particle having an internal reversed bicontinuous cubic phase structure (primitive surface, space group Im-3m), adapted from Sagalowicz et al. [97], (d) Cryo-TEM of a vesicle, which is obtained by dispersing a lamellar liquid crystalline phase into water; (e) Cryo-TEM of a micellar phaseobtained from a Tween 80 solution; images and figure adapted partially from Sagalowicz et al. [61].


benefits for a given bioactive under certain conditions added to a certainmatrix, but may have a negative effect applied under (slightly) otherconditions. Recently, Feng et al. [74] studied vitamin E (present in itsstable acetate form) containing microemulsions based on nonionicemulsifiers. Focus was put on determining the release rate of vitamin Efrom the microemulsion using a dialysis bag-Ultraviolet Spectropho-tometer combination, and the evaluation of vitamin E cytotoxicitywhenladen microemulsions were exposed to human cancer cells. The resultsshow that the vitamin E microemulsion system induces a slightsustaining release effect when compared to the vitamin E release fromthe ethanol reference system. Moreover, cell toxicity of the microemul-sion was lower than that of the single components. Sim et al. [75]investigated the oxidation of methyl linoleate, an amphiphilic unsatu-rated oxidation sensitive model bioactive, when solubilized in Tweenbased o/wmicroemulsions in the presence of a chlorogenic acid and α-tocopherol antioxidant mixture. Understanding the synergistic effectsbetween these two types of ingredients is of great interest when tryingto develop new strategies for increasing the stability of oxidationsensitive nutrients. The presented results demonstrate that chlorogenicacid and vitamin E exhibit a strong synergetic effect. This may haveimplications for the nutritional values of products, which containchlorogenic acid and its analogues, such as coffee. However, we stillneed a better insight in themechanismof the synergistic action in orderto use these results for the development of other potent antioxidantmixtures. Moreover, more systematic data are needed to betterunderstand the differences observed in the antioxidant activity as afunction of structure formation (e.g. bulk vs emulsions vs microemul-

sions). Zhang et al. [76] published, recently, a study on antimicrobialperformance against Bacillus subtilis (a foodborne bacterial pathogen)of a microemulsion system which consisted of glycerol monolaurateGML) as the oil, Tween 20 as the surfactant, ethanol as the cosurfactant,sodium lactate (SL) and water. The obtained results showed that theusedmicroemulsion formulationswere effective in inhibiting the viablebacteria cells and the bacteria growth, and that the solubilization of SLinto themicroemulsion created a synergistic antimicrobial activity. Thiswork indicates that microemulsions are promising delivery vectors alsofor antimicrobial applications for the food industry. However, also inthis case we need more insight in the molecular mechanism and thecontribution of the interface present in microemulsion systems.

6.2. Liposomes

Liposomes, often also denoted as vesicles, are formed when thesurfactant molecules have a Packing parameter P close to 1. Contraryto microemulsions their formation is often not completely spontane-ous. When mixed with water the surfactant spontaneously forms alamellar phase, which then needs to be dispersed to form vesicles.Liposomes can contain (i) one bilayer forming unilamellar vesicles(ULV), (ii) several concentric bilayers forming multi lamellar vesiclesor (iii) non concentric bilayers formingmulti vesicular vesicles (MVV).The size of these structures can be rather small (in the range of 20 nm)or rather large (exceeding 1 μm). Themost commonprocedure to formvesicles consists of evaporating a surfactant, such as phospholipid orcholesterol, chloroform/methanol solution to form a phospholipid-

Fig. 5. Top: Cryo-TEM image of vesicles formed when D1 is mixed with water. Bottom:Cryo-Tem image of the rod-like micelles formed when D2 is mixed with water.


based film [77]. The subsequent addition of an aqueous phase andshear is necessary to obtain the vesicle dispersion. Due to the use oftoxic solvents, this method is not adapted to food. However, othermethods are also available, such as using a microfluidizer, ormembrane extrusion.

So far, a lot of delivery applications have been developed for thepharmaceutical industry. In principle, liposomes can encapsulatehydrophilic molecules in their inner aqueous compartment whileamphiphilic and/or lipophilic ingredients can be delivered inside thebilayer structure. A great variety of natural and synthetic moleculescan be used allowing also targeted delivery [77]. Attachment of PEGmoieties, for example, on the vesicle surface, prevents them frombeing destroyed by monocites and macrophages in the liver andspleen ensuring prolonged circulation in the blood stream.

The use of vesicles or liposomes in food applications is still todayquite limited. This is most probable due to (i) the relatively high costsof pure lecithins, the best surfactant for making food liposomes, (ii)the relatively low encapsulation efficiency and (iii) the relativecomplicated fabrication equipment. Most prominent application infood industry is for the encapsulation of cheese ripening enzymes inorder to improve the enzymatic function and enabling a homoge-neous repartition of the enzyme within the cheese product [78,79].

In a recent study, Folmer et al. [4] investigated the uptake oftocopherol using a Caco-2 cell model. The main idea was to find outwhether differences in structure formation and/or hydrophilicity of theused tocopherol derivative would induce a different tocopherol uptakebehaviour. Twoα tocopherol succinate derivatives, where two differenthydrophilic ethyleneglycol chains were attached to the tocopherolsuccinate, were used. Those are the tocopherol hexaethylene glycolsuccinate (denoted as D1), which forms vesicles in water, and thetocopherol dodecaethylene glycol succinate (denoted as D2), whichforms elongated micelles in water (Fig. 5). D1 or D2 were eithersolubilized into mixed micelles using bile (taurocholate) acids, mono-oleins, lysophosphatidylcholine and oleic acid or used as such in water.When, the derivatives were solubilized intomixedmicelles, D1 showeda slightly but significantly more efficient esterase transformation intotocopherol and tocopherol succinate and subsequent uptake of theseconstituants into the cells than D2. This must be related to the differentefficiency of the hydrolytic reaction of the esterase. The situation wascompletely changed when D1 and D2 were just mixed into water (andnot incorporated into mixed micelles). In this case, the total hydrolysisand uptake into the cells was about two folds lower for D1 than for D2.Obviously, elongated micelle structures are much more efficient thanvesicles in terms of tocopherol bioavailability. This result demonstratesthat the type of the formed self-assembly structure can also play acrucial role in determining the bioactivity of active ingredients such astocopherol.

6.3. Dispersed reversed self-assembly structures

Reversed phases are made out of surfactants that have a Packingparameter P>1 (see Fig. 4). They are formed by lipophilic surfactantssuch as unsaturated monoglycerides or phospholipids. One of the moststudied reversed system is the reversed bicontinuous cubic phase.Possible applications, suchas formolecularprotection, controlled release,prevention of molecular aggregation or changes in chemical reactionwere demonstrated in the past and seem to be particularly attractive tothe pharmaceutical or cosmetic industry [80]. One of themain features ofthe cubic phase is its high viscosity which makes it difficult to handleand to use. However, Larsson and co-workers found efficient means todisperse these reverse structures into water making them also availableas delivery systems for aqueous liquids [81–83]. Two limitations stillremain. Firstly, taste issues may appear if a certain threshold concentra-tion in the final aqueous product is exceeded, and secondly, it wasdemonstrated that when a dispersion of a bicontinuous cubic phase (aso-called cubosome dispersion) is mixed with an emulsion, a new type

of dispersion is formed, in which the inner structure of the dispersedparticles was not anymore bicontinuous cubic [84].

More recently also other reversed phases and their dispersionswerestudied in more depth. Examples are the reversed hexagonal phase(Hii), the reversed micellar cubic phase (space group Fd-3m) thereversed microemulsion and the sponge (L3) phase [85–89]. Interest-ingly enough, the functionality of these phases was very different andclearly depended on their nanostructure: for instance, the reversedhexagonal phase showed amore sustained release than the cubic phase,and the glucose diffusion coefficient was about 10 times lower in thereversed hexagonal phase than in the bicontinuous cubic phase [90,91].Release of entrapped/solubilized molecules can also be tuned byswitching from one phase to another one by, for instance, changingtemperature inducing a transition from, e.g. cubic to hexagonal [91].Reversed hexagonal and micellar cubic phases contain, like the cubicphase, a large amounts of surfactant and thereforehave some limitationsfor use in food products, essentially when a relatively large amounts ofdelivery system has to be added in order to create the desired finalbenefit in the product or during consumption.

In this respect, reversed microemulsion dispersions can beobtained with much less surfactants. These structures are quiteattractive, since new functionalities, which are associated with theunique internal microemulsion structure of the oil droplets, could becreated. For example, it was shown that reverse microemulsiondroplets can solubilize non-esterified phytosterol molecules in muchlarger amounts than in ordinary oil droplets can do. Michel et al. [92]reported that 15% phytosterol could be solubilized in molecular forminto reversed microemulsion droplets dispersed in milk withoutinducing significant re-crystallisation of the phytosterol over timewhile the same amount of phytosterol could not be solubilized innormal oil droplets without recrystallizing (Fig. 6). Another interest-ing application of reversed microemulsion droplets deals with thecontrolled release of aromas. In particular, when reducing oils and fatsin food products, aroma release gets unbalanced and amphiphilic andlipophilic aroma molecules are subjected to a so-called ‘burst’ release.

Fig. 6. Polarized light microscopy of milk where (left) the oil was loaded with non-esterified phytosterols prior to homogenization, and (right) a reversed microemulsion phase wasloadedwithnon-esterifiedphytosterols prior to homogenization. In polarizedmicroscopy, non crystallised oil droplets are not visible. Imageswere taken after severalweeksof storage at4 °C. Notice that for the O/W emulsion (left), there are many phytosterol crystals visible while for the dispersed reversed microemulsion (right), there is no phytosterol crystal.


In the past it was shown that a bulk reversed bicontinuous cubic phasecontaining 20 or 30% water generates a unique release profile ofaromas when compared to the profile obtained with other structures,such as oils or w/o emulsions [93]. More recently, Landy et al. [94]investigated the release of individual aromamolecules in more detailsby means of gas chromatography mass spectrometry (GC–MS). Therelease from a water-in-oil microemulsion (10% water–60% unsatu-rated monoglyceride) was compared to the release from a water-in-oil emulsion (10% water–5% polyglycerol polyricinoleate (PGPR)–85%sunflower oil) and from pure sunflower oil. For almost all usedlipophilic aromas the release from the microemulsion was less thanfrom the oil and from the emulsion. The results were especiallyimpressive for octanol and butanol, two aroma molecules withamphiphilic character (Fig. 7). Phan et al. [95] looked at the staticand dynamic release behaviour of a dispersed water-in-oil micro-emulsion (composition: 0.25% unsaturated monoglyceride–4.75%medium chain triglyceride (MCT)–0.8% sodium caseinate–94.2%water) compared to a normal oil-in-water emulsion (5% medium

Fig. 7. Release of aroma molecules into the headspace using a water-in-oil microemulsion (LLogP is representing the octanol-water partitioning coefficient of the different aroma molsolubilization into octanol. The release data were normalized by the corresponding releaseboth the microemulsion and emulsion is less than the one from the pure oil. More impormolecules, the release from the microemulsions is about half of the release measured from tmicroemulsion, which is able to solubilize surface active molecules and thereby significantAdapted from Landy et al. [94].

chain triglyceride (MCT)–0.8% sodium caseinate–94.2% water). It wasfound that the aroma release from the dispersed microemulsion waslower and the release dynamics delayed when compared to therelease from the corresponding emulsion. Clearly, the presence of ahigh interfacial area within the microemulsion system significantlyinfluences (and slows down) the release behaviour of aromamolecules when compared to the corresponding oil or emulsionsystem.

7. Conclusion and outlook

In this work we presented and described various types of deliverysystems which are used for the fortification of liquid food products.They all have advantages and limitations as depicted and summarizedin Fig. 1. Most delivery systems are able to solubilize lipophilicnutrients into aqueous products. Concerning the appearance of thefinal food product, only nanoemulsions, microemulsions and somecomplexes are able to keep the product transparent, if desired

2) and a water-in-oil emulsion (w/o) as a function of logP of the used aroma molecules.ecules. Low LogP means good solubilization into water; while high LogP means largefrom pure medium chain triglyceride (MCT) oil. It can be noticed that the release fromtant to see is that, for butanol and octanol, which are two quite surface active aromahe emulsion system. These effects can be attributed to the large interface present in thely changing the release behaviour of interfacially active aromas into the headspace.


especially for some beverage formulations. Most of the describedsystems suffer either (i) from some regulatory issues concerning theused carrier material, or (ii) from an insufficient loading capacityrestricting their use for the delivery of nutrients in only smallconcentrations. Most challenging, however, is to achieve also anappropriate chemical stability of the delivered active ingredientsduring the shelf-life of the liquid product. Realizing a sufficientchemical stability of the delivered nutrients and aromas in thefortified end product is probably themost desired functionality that thedelivery system must accomplish. We think that most probablysignificant technical advances in this field will come when we willbetter understand how chemically unstable nutrients, like the PUFAs orvitamins, are stored andprotected in their natural environment.Wealsobelieve that still much progress can be done when we will get a betterunderstanding of the origin and the full mechanism of the chemicaldegradation in each fortified product. In contrast to the delivery inpowderedproducts, it seems that for thedelivery of active ingredients inliquid products, there is no generic solution available which can solvemost of the delivery problems we are facing. Every solution is veryunique and depends very much (i) on the final product matrix andpackaging, (ii) on the active ingredient(s) tobedeliveredand (iii) on thechosen delivery system and its physico-chemical properties.

References

[1] Palzer S. Food structures for nutrition, health andwellness. Trends Food Sci Technol2009;20:194–200.

[2] Loveday SM, Singh H. Recent advances in technologies for vitamin A protection infoods. Trends Food Sci Technol 2008;19:657–68.

[3] Tamayo-Esquivel D, Ganem-Quintanar A, Martinez AL, Navarrete-Rodriguez M,Rodriguez-Romo S, Quintanar-Guerrero D. Evaluation of the enhanced oral effectof omapatrilat monoolein nanoparticles prepared by the emulsification-diffusionmethod. J Nanosci Nanotechnol 2006;6:3134–8.

[4] Folmer BM, Baron D, Hughes E, Miguet L, Sanchez B, Heudi O, et al. Monocomponenthexa- and dodecaethylen glycol succinyl-tocopherol esters: self-assembly structures,cellular uptake and sensitivity to enzyme hydrolysis. Biochem Pharmacol 2009;78:1464–74.

[5] Acosta E. Bioavailability of nanoparticles in nutrient and nutraceutical delivery.Curr Opin Colloid Inter Sci 2009;14:3–15.

[6] Gouin S. Microencapsulation: industrial appraisal of existing technologies andtrends. Trends Food Sci Technol 2004;15:330–47.

[7] Wegmuller R, Zimmermann MB, Buhr VG, Windhab EJ, Hurrell RF. Development,stability, and sensory testing of microcapsules containing iron, iodine, and vitaminA for use in food fortification. J Food Sci 2006;71:S181–7.

[8] Ubbink J, Schooman A. Flavor delivery systems. Kirk-Othmer Encyclopedia ofChemical Technology; 2003.

[9] Augustin MA, Y.H. Nano- and micro-structured assemblies for encapsulation offood ingredients. Chem Soc Rev 2009;38:902–12.

[10] Gharsallaoui A, Roudauta G, Chambina O, Voilleya A, Saurela R. Applications ofspray-drying in microencapsulation of food ingredients: an overview. Food Res Int2007;40:1107–21.

[11] Mulder AM, Connellan PA, Oliver CJ, Morris CA, Stevenson LM. Bovine lactoferrinsupplementation supports immune and antioxidant status in healthy humanmales. Nutr Res 2008;28:583–9.

[12] Saladino R, Giampiero G, Farina A, Crestini C, Nencioni L, Palamara AT. Advancesand challenges in the synthesis of highly oxidized natural phenols with antiviral,antioxidant and cytoxic activities. Curr Med Chem 2008;15:1500–19.

[13] Sies H, Stahl W. Beta-carotene, and other carotenoids as antioxidants. Am J ClinNutr 1995;62:1315S–21S.

[14] Hsieh AT, Anthony JC, Diersen-Schade DA, Rumsey SC, Lawrence P, Li C, et al. Theinfluence of moderate and high dietary long chain polyunsaturated fatty acids(LCPUFA) on baboon neonate tissue fatty acids. Pediatr Res 2007;61.

[15] McClements DJ, Decker EA, Park Y, Weiss J. Structural design principles fordelivery of bioactive components in nutraceuticals and functional foods. Crit RevFood Sci Nutr 2009;49:577–606.

[16] Lesmes U, McClements DJ. Structure–function relationships to guide rationaldesign and fabrication of particulate food delivery systems. Trends Food SciTechnol 2009;20:448–57.

[17] Hoppe PP, Krennrich G. Bioavailability and potency of natural source and all-racemic alpha-tocopherol in the human: a dispute. Eur J Nutr 2000;39:183–93.

[18] Byers T, Perry G. Dietary carotenes, vitamin C, and vitamin E as protectiveantioxidants in human cancers. Annu Rev Nutr 1992;12:139–59.

[19] Serfert Y, Drusch S, Schwarz K. Chemical stabilisation of oils rich in long-chainpolyunsaturated fatty acids during homogenisation, microencapsulation andstorage. Food Chem 2009;113:1106–12.

[20] Ogawa S, Decker EA, Mcclements DJ. Production and characterization of O/Wemulsions containing cationic droplets stabilized by lecithin-chitosan mem-branes. J Agric Food Chem 2003;51:2806–12.

[21] Djordjevic D, Cercaci L, Alamed J, McClements DJ, Decker EA. Chemical and physicalstability of citral and limonene in sodium dodecyl dultat-chitosan and Gum Arabic-stabilized oil-in-water emulsions. J Agric Food Chem 2007;55:3585–91.

[22] Shaw LA, McClements DJ, Decker EA. Spray-dried multilayered emulsions as adelivery method for omega 3 fatty acids into food systems. J Agric Food Chem2007;55:3112–9.

[23] Muschiolik G. Multiple emulsions for food use. Curr Opin Colloid Interface Sci2007;12:213–20.

[24] Benichou A, Aserin AA, Garti N. W/O/W double emulsions stabilized with WPI–polysaccharide complexes. Colloids Surf A Physicochem Eng Asp 2007;294:20–32.

[25] Fechner A, Knoth A, Scherze I, Muschiolik G. Stability and release properties ofdouble-emulsions stabilised by caseinate–dextran conjugates. Food Hydrocolloids2007;21:943–52.

[26] Pimentel-Gonzáleza DJ, Campos-Montielb RG, Lobato-Callerosc C, Pedroza-Islas R,Vernon-Cartera EJ. Encapsulation of Lactobacillus rhamnosus in double emulsionsformulated with sweet whey as emulsifier and survival in simulated gastrointes-tinal conditions. Food Res Int 2009;42:292–7.

[27] Utada AS, Lorenceau E, Link DR, Kaplan PD, Stone HA, Weitz DA. Monodispersedouble emulsions generated from a microcapillary device. Science 2005;308:537–41.

[28] Hanson JA, Chang CB, Graves SM, Li Z, Mason TG, Deming TJ. Nanoscale doubleemulsions stabilized by single-component block copolypeptides. Nature 2008;455:85–8.

[29] Solans C, Zquierdo PI, Nolla J, Azemar N, Garcia-Celma MJ. Nano-emulsions. CurrOpin Colloid Interface Sci 2005;10:102–10.

[30] Gutiérrez JM, González C, Maestro A, Solè I, Pey CM, Nolla J. Nano-emulsions: newapplications and optimization of their preparation. Curr Opin Colloid Interface Sci2008;13:245–51.

[31] Solé I, Maestro A, Pey CM, Gonzalez C, Solans C, Gutierrez JM. Nano-emulsionspreparation by low energy methods in an ionic surfactant system. Colloids Surf APhysicochem Eng Asp 2006;288:138–43.

[32] Pey CM, Maestro A, Soléa I, González C, Solans C, Gutiérrez JM. Optimization ofnano-emulsions prepared by low-energy emulsification methods at constanttemperature using a factorial design study. Colloids Surf A Physicochem Eng Asp2006;288:144–50.

[33] Wooster TJ, Golding M, Sanguansri P. Impact of oil type on nanoemulsionformation and Ostwald ripening stability. Langmuir 2008;24:12758–65.

[34] WangX, JiangY,WangYW,HuangMT,HoaCT,HuangQ. Enhancinganti-inflammationactivity of curcumin through O/W nanoemulsions. Food Chem 2008;108:419–24.

[35] Wulff-PérezM, Torcello-Gomez A, Galvez-RuızMJ,Martın-Rodrıguez A. Stability ofemulsions for parenteral feeding: preparation and characterizationof o/w nanoe-mulsions with natural oils and Pluronic f68 as surfactant. Food Hydrocolloids2009;23:1096–102.

[36] Yuan Y, Gao Y, Zhao J, Mao L. Characterization and stability evaluation of beta-carotene nanoemulsions prepared by high pressure homogenization undervarious emulsifying conditions. Food Res Int 2008;41:61–8.

[37] McClements DA, Decker EA, Weiss J. Emulsion-based delivery systems forlipophilic bioactive compounds. J Food Sci 2007;72:R109–23.

[38] Weiss J, Decker EA, McClements DJ. Solid lipid nanoparticles ad delivery systemsfor bioactive food component. Food Biophys 2008;3:146–54.

[39] Wong HL, Li Y, Bendayan R, Rauth MA, Xiao YW. In: Amiji MM, editor. Solid lipidnanoparticles for anti-tumor drug delivery. Nanotechnol Cancer TherLondon: CRCPress; 2007. p. 742–75.

[40] Bunjes H, Steiniger F, Richter W. Visualizing the structure of triglyceridenanoparticles in different crystal modification. Langmuir 2007;23:4005–11.

[41] Bunjes H, Koch MHJ. Saturated phospholipids promote crystallization but slowdown polymorphic transitions in triglyceride nanoparticles. J Control Release2005;107:229–43.

[42] Carlotti ME, Sapini S, Trotta M, Battaglia L, Vione D, Pelizzit E. Photostability andstability over time of retynil palmitate in an O/W emulsion in SLN introduced inthe emulsion. J Dispers Sci Technol 2005;26:125–38.

[43] Yang SC, Zhu JB. Preparation and characterization of Camptotechin solid lipidnanoparticles. Drug Dev Ind Pharm 2002;28:265–74.

[44] Souto EB, Müller RH. Cosmetic features and application of lipid nanoparticles (SLN,NLC). Int J Cosmet Sci 2008;30:157–65.

[45] Buschmann HJ, Schollmeyer E. Applications of cyclodextrins in cosmetic products:a review. J Cosmet Sci 2002;53:185–91.

[46] Davis ME, Brewster ME. Cyclodextrin-based pharmaceutics: past, present andfuture. Nat Rev Drug Discov 2004;3:1023–35.

[47] Rasheed A, Ashok Kumar CK. Cyclodextrins as drug carrier molecule: a review.Scienta Pharmaceutica 2008;76:567–98.

[48] Del Valle EMM. Cyclodextrins and their uses: a review. Process Biochem 2004;39:1033–46.

[49] Hedges RA. Industrial applications of cyclodextrins. Chem Rev 1998;98:2035–44.[50] Lin HS, Chean CS, Ng CY, Chan SY, Ho PC. 2-Hydroxypropyl-beta-cyclodextrin

increases aqueous solubility and photostability of all trans-retinoic acid. J ClinPharm Ther 2000;25:265–9.

[51] Munoz-Botella S, Martin MA, Del Castill B, Lerner BA, Menendez JC. Differentiatinggeometrical isomers of retinoids and controlling their photo-isomerization bycomplexation with cyclodextrins. Anal Chim Acta 2002;468:161–70.

[52] Choi MJ, Soottitantawat A, Nuchuchua O, Min SG, Ruktanonchai U. Physical andlight oxidative properties of eugenol encapsulated by molecular inclusion andemulsion–diffusion study. Food Res Int 2009;42:148–56.

[53] Choi MJ, Rutkanonchai U, Soottitantawat A, Sang-Gi M. Morphological character-ization of encapsulated fish oil with beta-cyclodextrin and polycaprolactone. FoodRes Int 2009;42:989–97.


[54] Conde-Petit B, Escher F, Nuessli J. Structural features of starch-flavor complexationin food model systems. Trends Food Sci Technol 2006;17:227–35.

[55] Semo E, Kesselman E, Danino D, Livney YD. Casein micelle as a natural nano-capsular vehicle for nutraceuticals. Food Hydrocolloids 2006;21:936–42.

[56] Zimet P, Livney YD. Beta-lactoglobulin and its nanocomplexeswith pectin as vehiclesfor omega-3 polyunsaturated fatty acids. Food Hydrocolloids 2009;23: 1120–6.

[57] Livney Y. D., Current Opinion in Colloid & Interface Science; This issue.[58] Krog NJ. In: Friberg SE, Larson K, editors. Food emulsions. New York, Basel: Marcel

Dekker, Inc; 1997. p. 141–88.[59] Leser ME, Sagalowicz L, Michel M, Watzke HJ. Self-assembly of polar food lipids.

Adv Colloid Interface Sci 2006;123:125–36.[60] Larsson K. Cubic lipid–water phases: structures and biomembrane aspects. J Phys

Chem 1989;93:7304–14.[61] Sagalowicz L, Leser ME, Watzke HJ, Michel M. Monoglyceride self-assembly

structures as delivery vehicles. Trends Food Sci Technol 2006;17:204–14.[62] Sagalowicz L, Mezzenga R, Leser ME. Investigating reversed liquid crystalline

mesophases. Curr Opin Colloid Interface Sci 2006;11:224–9.[63] Israelachvili JN, Marcelja S, Horn RG. Physical principles of membrane organiza-

tion. Q Rev Biophysics 1980;I3(2):121–80.[64] Tanford C. The hydrophobic effects: formation of micelles and biological

membranes. New York: John Willey; 1980.[65] Ericsson B, Eriksson PO, Löfroth JE, Engström S. Cubic phases as delivery systems

for peptide drugs. Washington: American Chemical Society; 1991. p. 251–65.[66] Vauthey S, Milo C, Frossard P, Garti N, Leser ME, Watzke HJ. Structured fluids as

microreactors for flavor formation by the Maillard reaction. J Agric Food Chem2000;48:4808–16.

[67] Yaghmur A, Aserin A, Garti N. Furfural-cysteine model reaction in food gradenonionic oil/water microemulsions for selective flavor formation. J Agric FoodChem 2002;50:2878–83.

[68] Lutz R, Arserin A, Garti N. Maillard reaction between leucine and glucose in O/Wmicroemulsion media in comparison to aqueous solution. J Dispers Sci Technol2005;26:533–47.

[69] Flanagan J, Singh H. Microemulsions: a potential delivery system for bioactives infood. Crit Rev Food Sci Nutr 2006;46:221–37.

[70] Garti N, Spernath A, Aserin A, Lutz R. Nano-sized self-assemblies of nonionicsurfactants as solubilization reservoirs and microreactors for food systems. SoftMatter 2005;1:206–18.

[71] Garti N, Yuli-Amar I. Micro- and nano-emulsions for delivery of functional foodingredients. In: Garti N, editor. Delivery and controlled release of bioactives in foodsand nutraceuticals. Cambridge: Woodhead Publishing Limited; 2008. p. 149–83.

[72] Garti N, Yaghmur A, Arserin A, Spernath A, Elfakess R, Esrahi S. Solubilization ofactive molecules in microemulsion for improved environmental protection.Colloids Surf A Physicochem Eng Asp 2004;230:159–68.

[73] Szymula. Atmospheric oxidation of beta-carotene in aqueous, pentanol, SDSmicroemulsion systems in the presence and absence of vitamin C. J Dispers Technol2004;25:129–37.

[74] Feng JL, WuWang Z, Zhang J, NiWang Z, Liu F. Study on food-grade vitamin Emicroemulsions based on nonionic emulsifiers. Colloids Surf A Physicochem EngAsp 2009;339:1–6.

[75] Sim WLS, Han MY, Huang D. Quantification of antioxidant capacity in amicroemulsion system: synergistic effects of chlorogenic acid with α-tocopherol.J Agric Food Chem 2009;57:3409–14.

[76] Zhang H, Shen Y, Bao Y, He Y, Feng F, Zheng X. Characterization and synergisticantimicrobial activities of food-grade dilution-stable microemulsions againstBacillus subtilis. Food Res Int 2008;41:495–9.

[77] Soussan E, Cassel S, Blanzat M, Rico-Lattes I. Drug delivery by soft matter: matrixand vesicular carriers. Angew Chem 2009;48:274–88.

[78] Mozafari MR, Johnson C, Hatzianzoniu S, Demetzos C. Nanoliposomes and theirapplication in food nanotechnology. J Liposome Res 2008;18:309–27.

[79] Taylor TM, Davidson PM, Bruce BD, Weiss J. Liposomal nanocapsules in foodscience and agriculture. Crit Rev Food Sci Nutr 2005;45:587–605.

[80] Shah JC, Sadhale Y, Dakshina MC. Cubic phase gels as drug delivery systems. AdvDrug Deliv Rev 2001;47:229–50.

[81] Landh T. Phase behavior in the system pine oil monoglycerides-poloxamer 407-water at 20 °C. J Phys Chem 1994;98:8453–67.

[82] Gustafsson J, Ljusberg-wahren H, Almgren M, Larsson K. Cubic lipid–water phasedispersed into submicron particles. Langmuir 1996;12:4611–3.

[83] Gustafsson J, Ljusberg-wahren H, Almgren M, Larsson K. Submicron particles ofreversed lipidphases inwater stabilizedby anonionic amphiphilicpolymer. Langmuir1997;13:6964–71.

[84] Moitzi C, Guillot S, Fritz G, Salentinig S, Glatter O. Phase reorganiszation in self-assembled systems through interparticle material transfer. Adv Mater 2007;19:1352–8.

[85] Yaghmur A, de Campo L, Sagalowicz L, Leser ME, Glatter O. Emulsifiedmicroemulsions and oil-containing liquid crystalline phases. Langmuir 2005;21:569–77.

[86] Yaghmur A, de Campo L, Salentinig S, Sagalowicz L, Leser ME, Glatter O. Oil-loadedmonolinolein-based particles with confined inverse discontinuous cubic structure(Fd3m). Langmuir 2006;22:517–21.

[87] Barauskas J, Johnsson M, Tiberg F. Self-assembled lipid superstructures: beyondvesicles and liposomes. Nano Lett 2005;5:1615–9.

[88] Barauskas J, Misiunas A, Gunnarsson T, Tiberg F, Johnsson M. “Sponge”nanoparticle dispersions in aqueous mixtures of diglycerol monooleate, glyceroldioleate, and polysorbate 80. Langmuir 2006;22:6328–34.

[89] Lutz R, Arserin A, Watchel EJ, Ben-Shoshan E, Danino D, Garti N. A study of theemulsified microemulsion by SAXS, Cryo-TEM, SD-NMR, and electrical conduc-tivity. J Dispers Sci Technol 2007;28:1149–57.

[90] Lee KWY, Nguyen TH, Hanley T, Boyd BJ. Lyotropic liquid crystalline phasesformed from glycerate surfactants as sustained release drug delivery system. IntJ Pharm 2009;365:190–9.

[91] Fong WK, Hanley T, Boyd BJ. Stimuli responsive liquid crystals provide “ondemand” drug delivery in vitro and in vivo. J Control Release 2009;135:218–26.

[92] Michel M, Watzke HJ, Sagalowicz L, Kolodziejczyk E, Leser ME. In: Dickinson E,Leser ME, editors. Food colloids. Self-assembly and materials science, vol. 302.Cambridge: Royal society for chemistry; 2007. p. 19–33.

[93] Vauthey S, Visani P, Frossard P, Garti N, Leser ME, Watzke HJ. Release of volatilesfrom cubic phases monitoring by gas sensors. J Dispers Sci Technol 2000;21:263–78.

[94] LandyP, Polien P, Rytz A, LeserME, Sagalowicz L, Blank I.Model studies on the releaseof aroma compounds from structured and nanostructured oil systems using proton-transfer reaction mass spectroscopy. J Agric Food Chem 2007;55:1915–22.

[95] Phan VA, Liao YC, Antille A, Sagalowicz L, Robert F, Godinot N. Delayed volatilecompound release properties of self-assembly structures in emulsions. J AgricFood Chem 2008;56:1072–7.

[96] Jönsson B, Lindman B, Holmberg K, Kronberg B. Surfactants and polymers inaqueous solution. Chichester, England: John Wiley & son; 1998.

[97] Sagalowicz L, Michel M, Adrian M, Frossard P, Rouvet M, Watzke HJ, et al.Crystallography of dispersed self-assembly structures studied by cryo-transmissionelectron microscopy. J Microsc 2006;221:110–21.

Sagalowicz & Leser 2010_Delivery Systems for Liquid Food Products

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