nanotechnology in the food industry - ernährungs · pdf filehaviour with electromagnetic...

44 Ernaehrungs Umschau international | 4/2013

Science & Research | Original Contribution

Nanotechnology in the Food IndustryJochen Weiss, Monika Gibis, Stuttgart-Hohenheim

Introduction

The science of applied nano-technol-ogy is concerned with the character-isation, production and targetedmodification of naturally-occurringor synthetically manufactured ma-terials at the atomic, molecular orcolloidal level [1]. While the originaldefinition of nanotechnology re-ferred to all structures having acharacteristic size of less than 100nanometres (10–7 m) in at least onedimension (see glossary), in recentyears the definition of nano-struc-

tured materials has been limited tomaterials which show entirely newphysical and chemical properties andwhich therefore differ considerablyfrom macro-scaled materials withthe same chemical structure [2].

These divergent properties of nano-scaled materials are frequently theresult of extreme surface-to-vo-lume ratios of the particles and arethe reason why boundary layer phe-nomena are decisive for the physicaland chemical properties of these ma-terials [3]. Thus, for example, manynano-scaled materials have a sub-stantially higher chemical reactivityand entirely different interaction be-haviour with electromagnetic wavesthan macroscopically structuredmaterials. These different propertiesnecessitate special toxicological con-siderations [2] (� Overview 1). At thesame time, however, these representthe basis for special industrial appli-

cations and possible advantages forthe consumer. Besides machine pro-duction, electrical engineering, tex-tile finishing and pharmaceutics, thisalso applies to the food industry [1,3–8]. The present contribution willfocus primarily upon applications inthe food industry.

Indirect applications ofnanotechnology in food-stuffs

Four principal potential applicationsof nanotechnology in which inten-sive research is currently in progresscan be identified in the food indus-try: packaging, process technology,microbiology and ingredients (� Fig-ure 1) [5, 8]. Its use in foodstuffs canbe classified as “direct” or “indirect”.

Direct use refers to the integrationof nano-structured substances andmaterials in foodstuffs and mustalso be declared as such.

Indirect use includes e.g. the use ofnano-structured materials in pack-aging technology [4] or the use of ef-ficiently nano-structured catalysersfor the hydration of fats [9, 10]. Itcan therefore be expected that themajority of applications of nano -technology are concerned with itsindirect use.

It should be noted that in indirectuse no nano-structured materials aredirectly incorporated in the foods-tuff matrix. However, the materialscome into contact with the foodstuff[2, 11]. The reason is that the mate-rials must be in contact with thefoodstuff in order to fulfil a certainfunction benefitting the foodstuff or

Peer-reviewed | Manuscript received: December 19, 2011 | Revision accepted: February 10, 2013

SummaryExtreme surface-to-volume ratios of the particles are characteristic of nano-scaledmaterials. Compared with macro-scaled materials, this results in entirely differentphysical and chemical properties. These are the basis of the special applicationsand also the cause of the possible risks with nano-materials. The present overviewdeals above all with the four main areas of use in the food industry: packaging, pro-cess technology, microbiology and ingredients. On the one hand, we must dis-tinguish between inorganic and organic nano-materials and, on the other hand,between the direct and indirect use of nano-materials in connection with food-stuffs. Besides research investigating new applications, toxicological investiga-tions, for example for influencing bioavailability and the metabolism of nano-scaled substances, are required. Due to the special material properties, this also de-mands new analytical procedures.

Keywords: Nano-scaling, food technology, bioavailability, toxicology, food analysis

Citation: Weiss J, Gibis M (2013) Nano-technology in the food industry.Ernaehrungs Umschau internatio-nal 60(4): 44–51

This article is available online:DOI: 10.4455/eu.2013.011

Author's copy!Any use beyond the limits of copyright law without the consent of the publisheris prohibited and punishable. This applies in particular to duplications, transla-tions, microfilming as well as storage and processing in electronic systems.

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Ernaehrungs Umschau international | 4/2013 45

the foodstuff production, such asthe catalysed hydration of fats withlow trans-fatty acid contents. Specialattention must therefore be given tothe possible transfer of nano-structured materials to foodstuffs[2]. Such a transfer must be exclud -ed in order to use these materials ascontact materials or auxiliary pro-cess materials.

Use in packaging technology

For a number of years nanotechno-logical approaches have been used toimprove the functional properties ofpackaging materials [4, 12–14]. Theprincipal focus is upon the develop-ment of new packaging materialswhich prolong the shelf lives offoodstuffs as a result of improvedprotective functions (� Figure 1).Thus, for example, the inclusion ofimpermeable nano-scaled bleachingearth mono-layers incorporated in acompound following chemical mod-ification can reduce gas exchange(oxygen, nitrogen, carbon dioxide,etc.) with the environment [8].

Besides improving the barrier func-tion of the packaging material, theincorporation of nano-scaled struc-tures also substantially improves themechanical properties of the packag-ing, such as the abrasion resistance[4].

Nano-scaled carrier systems foranti-oxidants and preservatives in-corporated in packaging materialscan transform “passive” packagingto “active” packaging and thus pro-long the shelf life of the foodstuffs[15, 16]. The incorporation of nano-sensors and tracers which, with theirincreased sensitivity, can recogniseand indicate even the smallestchanges in the packaged goods (e.g.rotting or interruption of the refrig-eration chain), make possible intelli-gent packaging able to indicate thepresence of oxidation products ormicrobiologically produced second-ary metabolites which can impair

the quality or safety of the food-stuffs [6, 15, 16].In addition, nanotechnology allowsthe modification of other function-alities, such as the processability ofpackaging machines, optical proper-ties (transparency), biological de-gradability, wetting behaviour andthe application of heat in microwaveovens.

Use in food processing technology

At the present time nanotechnologyfinds only limited use in food pro-cessing technology, although thissituation could rapidly change. New

research results which show dra-matically different catalysation be-haviour for nano-structured metalparticles offer particular promise [9].Accordingly, it would then be possi-ble not only to accelerate reactionsby a corresponding design, but alsoto control the reaction paths andconsequently the concentrations andtypes of the products generated.

Specific applications include the re-duced formation of trans-fatty acidsduring the hydration of fats and theaccelerated production of protein-carbohydrate conjugates for the sta-bilisation of foodstuff emulsions.

Overview 1: Toxicological aspects of nano-scaled materials (after [2])

– Up to now only little information is available on the subject of the spe-cific toxicokinetics/toxicology of nano-scaled substances. The investiga-tions of inorganic substances (metals, metal oxides, and titanium di-oxide) far outnumber the investigations of organic nano-structures.

– The substantially different reactivity compared with macro-scaled sub-stances creates analytical problems (detection, characterisation and mea-surement). Interactions with the surrounding matrix (e.g. foodstuffs)must therefore be taken into consideration.

– The tiny particle size and the high activity in small concentrations de-mand very time-consuming analytical procedures. Sufficient referencemethods and reference substances for calibration are, however, not yetavailable.

– The tiny size and the substantially different reactivity can result in diffe-rent absorption and distribution/accumulation behaviour in the organ-ism (passage of the blood brain barrier, placenta mobility, membranesolubility, interaction with transport molecules, etc.).

– The knowledge of biotransformation and the elimination of nano-sub-stances remain very limited.

– Nano-scaled substances can have catalytic properties or act as a crystal-lisation seed and influence the correct protein folding (tertiary or qua-ternary structure).

– The applicability and information value of existing toxicological test pro-cedures for use with nano-materials must be investigated. Thus, thefoodstuff additives titanium dioxide (E 171) and vegetable carbon (E153) in nano-scaled form are known to cause damage to the DNA, whichis not the case with macro-scaled forms.

– The activities of nano-scaled substances cannot be extrapolated frommacro-scaled or dissolved reference substances.

– Due to the lacking declaration obligation until now, knowledge of thetype and scope of nano-material applications is too limited, making theestimation of the exposure for consumers difficult.

Due to their very high surface-to-volume ratios and their well-definedstructures, many nano-structuresare particularly well suited for use asimmobilisation systems for enzymes[1, 17]. With the process known as“electrospinning” the application ofa high voltage to a polymer solutioncan, for example, produce nanofibreswith more or less porous core-shellstructures [18, 19]. With thisprocess it is possible to define the sizeof the core material, which can con-sist of enzymes, thus allowing pre-cise control over the material trans-port of the educts and the enzymes,as well as to remove the productswithout loss of the enzymes.

Besides their use in catalysis, nan-otechnological approaches have alsoled to improved separation processes[20]. Thus, the modification of thesurfaces of nano-structured filtermaterials results in better separatingcapacities and better specificities forthe materials separated.

Use in food microbiology

In the area of food microbiology (cf.� Box 1) there are two different fieldsof application (� Figure 1): (1) devel-oping nano-sensors and (2) improv-ing the effectiveness of preservatives,i.e. materials which inhibit thegrowth of or kill microorganisms[15, 19, 21–23]. However, as in thiscase nano-structures must be addeddirectly to the foodstuffs the latterapplication must be allocated to thedirect use of nanotechnology infoodstuffs.

Direct use of nanotechnol-ogy in foodstuffs

The direct application of nano-struc-tured materials in foodstuffs [5, 7,11, 24–29] is of particular interest.Possibilities exist here for the incor-poration of functional foodstuff in-gredients, such as fragrances,colouring agents, anti-oxidants,preservatives (see above) and biolog-

ically active components (vitamins,omega-3 fatty acids, polyphenols,etc.) in nano-structured particles orfibrous structures. In this respect,the possible advantages of improvedbioavailability must be weighedagainst the risks of a possible over-dosis (see below). This requires fur-ther research. Thus, the modificationof the pharmacokinetics of biologi-cally active materials for use in thesecarrier systems could require re-thinking of the permissible concen-trations, as the risk of over-dosageduring consumption then increases[7]. On the other hand, it is possiblethat the use of nano-scaled sub-stances reduces unwanted sub-stances, such as salt, fat or sugar, infoodstuffs.

The requirement for the use of newmaterial structures as functionalfoodstuff ingredients is justified bytheir frequently inadequate physicaland chemical stability in foodstuffmatrices [26, 27]. Due to theirchemical structure these ingredientscan be optimally incorporated in theexisting biological structures (cellsand cell compartments such as vac-uoles or membranes) of the startingmaterial, e.g. fresh fruit or vegeta-bles and thus stabilise these. On theother hand, in processed foods thesematerials are subject to rapid oxida-tion or polymerisation reactions fol-lowing their incorporation, detri-mentally affecting the quality of therespective foodstuff. The incorpora-tion of components in nano-struc-tured carrier systems can greatly re-duce the extent of such destabilisingreactions and prevent the physicalseparation of the components fromthe foodstuff matrix [29].

Contrary to inorganic nano-materi-als, which are predominantly used inchemistry and the material sciences,for direct use in foodstuffs only or-ganic substances approved for use infoodstuffs which are either brokendown in the human body analo-



Figure 1: Schematic overview of the potential areas of application for nanotech-nology in the food industry

chemical andenzymaticreactions

materialand heat transfer

separationprocesses

nanosensors

nanoparticles

nanofibres

nanoaggregates tracers

newadditives

newpackagingmaterials

preservatives

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gously to conventional ingredientsor directly eliminated come intoquestion. The justified toxicological reserva-tions in respect of inorganic nano-particles, such as silver or titaniumdioxide, mentioned overproportion-ately in the media preclude their di-rect use in foodstuffs [2].

Top-down and bottom-up foodproduction

One of the basic principles of nano -technology is the manufacture ofstructures by the “bottom-up prin-ciple” (� Figure 2). Contrary to thetop-down principle, in which rawmaterials are introduced to the foodproduct via conventional, above all,mechanical processes, such as mix-ing, grinding, separation and ag-glomeration, with the bottom-upprinciple structures comprised of in-dividual molecules are systemati-cally transformed to nano-struc-tures and micro-structures. Thesethen serve as the basic systems for the structure of the final foodproduct.

A key principle of bottom-up is theso-called self-assembly. This de-scribes the spontaneous formation ofordered thermodynamically stablestructures without the application ofclassical mechanical methods. An ex-ample of this is the formation ofemulsifier micelles [21]. These col-loidal particles are formed as soon asactive boundary-layer amphiphilicemulsifier molecules are introducedin sufficiently high concentrations toa polar solvent, such as water. Theredistribution of the hydrophobicemulsifier monomer groups into theinside of a spherical or cylindrical ag-gregate minimises the thermody-namically unfavourable interactionsbetween the polar solvent and thehydrophobic groups and maximisesthe thermodynamically favourableinteractions between the hydrophilicemulsifier head groups and the polar

solvent. The system is therefore ableto achieve a state in which the freeenergy is less than in the original dis-ordered state.

Exactly which structures can beformed by self-assembly dependsupon the chemical structure of theindividual molecules and the ambi-ent conditions (pH, temperature,ionic strength and pressure). Con-trolling the self-assembly requires avast knowledge of the molecular andcolloidal interactions (such as vander Waals, Coulomb, steric, deple-tion, hydration and hydrophobic in-teractions) [8].

Micelles are also capable of assimi-lating covalent components, for ex-ample anti-microbial ethereal oilshaving low solubility (also referredto as solubilisation) into their inte-rior structure. Assimilating thesesubstances enlarges the micelles,which are then referred to as loadedor swollen micelles or as microemul-sions [30].

In a further step it is necessary to de-velop an understanding for suchprocesses as phase separations, net-work formations and phase transi-tions which transform the self-as-

sembly structures produced, most ofwhich have sizes of the order of afew nanometres, to larger struc-tures. Only then can these be furtherprocessed by classical methods tofood products. It can therefore be ex-pected that in future a combinationof bottom-up and top-down food-stuff production will be increasinglyemployed in food technology.

Functional nano-structures in foodstuffs

Both the bottom-up principle de-scribed above and the top-downprinciple can be utilised for the pro-duction of the functional nano-structures used in food products.Fundamentally, one can distinguishbetween simple particulate nano-structures, so-called nanoparticles,nanofibres and complex nanoaggre-gates (� Figure 3) [5, 8, 24].

The nanoparticles used are predomi-nantly in the form of nano-emul-sions, i.e. oil in water or water in oildispersions, in which the meandroplet sizes are well below 100 nm.Because of their tiny droplet sizenano-emulsions do not tend towards

Box 1: Nanotechnology for the detection of pathogenic bacilli and toxins

The significant improvement in the detection of pathogenic bacilli or tox-ins produced by pathogenic bacilli which pose a danger to the safety ofthe foodstuff is one of the most important indirect applications of nano-technology in microbiology [6]. The superior qualitative and quantitativedetection of microorganisms and their metabolic products is once againbased upon the development of new materials, of which quantum dots,nano-composites, conductive polymers, Langmuir-Blodgett films and car-bon nanotubes deserve particular mention.

Here, above all the fact that nano-scaled detection systems have ex-tremely high sensitivities and very fast detection speeds is exploited. Thus,nano-sensors allow the in-situ determination of concentration with a de-tection sensitivity several orders of magnitude superior to that of conven-tional determinations and which, in the most favourable cases, yields a re-sult within only a few seconds. In the case of micro-biological organisms,for example, cell concentrations of 10–2 CFU/ml can be determined. For oli-gosaccharides the minimum concentrations which can be measured are ofthe order of less than 10–14 M, corresponding to around six molecules/µl.



creaming, are transparent and –when charged emulsifiers are used –frequently have an unusually highviscosity. Due to their transparencyconcentrated fragrance nano-emul-sions in which ethereal fragrancecomponents are encapsulated in anoil in water emulsion and which alsohave an anti-microbial effect in ad-dition to the fragrance, for example,are well suited as additives forcolourless beverage systems [31, 32].

The production of liquid nano-emul-sions from the melting of fats whichcrystallise following cooling resultsin so-called solid lipid nanoparticles.These are especially suitable as car-rier systems for bio-active sub-stances [29, 33, 34]. Thus, for ex-ample, beta carotene or vitamin D2

can be encapsulated in solid lipidnanoparticles in order to protectthem from light and oxidation. Herealso, their transparency makes them

suitable for use as nutritional sup-plements in colourless beverage sys-tems [34, 35]. Due to their surface-initiated crystallisation with triazylglycerides, solid lipid nanoparticlespossess unusual fat crystal struc-tures, which are particularly wellsuited for protecting chemically un-stable bio-active substances againstoxidation processes.

In principle, the bioavailability ofmany biologically active substancesin foodstuffs is low, for example as aresult of their bonding and incorpo-ration in cell compartments andstructures [33]. Both nano-emul-sions and solid lipid nanoparticles arecapable of improving the bioavail-ability of many biologically activesubstances, as nanoparticles possesslarge surfaces in relation to their vol-umes, enhancing their absorption inthe intestinal wall and allowing ef-fective micellation with the bile salts.Furthermore, nanoencapsulationalso suppresses a number of un-wanted interactions with the food-stuff matrix which reduce absorp-tion in the intestinal tract [26].

Alternatively to fat-based nanopar-ticles, it is also possible to producenano-structured hydrogel particles,for example by complex coacerva-tion or controlled biopolymer phaseseparation in combination withhigh-pressure homogenisation pro-cessing. Nanogel particles are suitedabove all as carrier systems for hy-drophilic substances, as a componentof multiple emulsions (e. g. water inoil in water) and for the formationof complex aggregates which canproduce new textural properties infoodstuffs. In this way, retinol hasbeen protected in silicone particleswith multiple emulsions (W/O/W)and by means of the sol-gel methodagainst light, heat and oxygen inorder to allow its use in pharmaceu-tical products and nutritional sup-plements [36].

Finally, the self-assembly systemsreferred to above, which – besides the

Figure 2: Top-down and bottom-up approaches for the production offoodstuffs

top-down andbottom-up

microstructures

nanostructures

foodstuffsraw materials from

the agricultural sector

peptidesproteinsoligosaccharidespolysaccharides

heatingmixinghomogenisingextruding, etc.

–COO–Ca2+–OOC–

conventional

processing technology

self-asse

mbly

covalent bondingelectrostatic interactionssalt bridgeshydrogen bridgeshydrophobic interactionsvan der Waals forces of attraction

phase transitionsnetwork formationphase separations

Figure 3: Functional nano-structures which come into question for use in foodstuffs

micro-emulsions

liposomes

nano-emulsions

solid nanoparticles

nanofibres

�


micelles – also include the phos-pholipid double-layer liposomesalso belong to the nanoparticles[23, 28, 37].

In addition to particulate sys-tems, current research is increas-ingly focussing upon the pro-duction of nanofibre structures(� Figure 3) [18, 19]. These can beproduced by either controlled di-rectionally oriented growth or byelectrospinning (see above) frompolymer solutions.

At the present time, the most in-tensive research is concernedwith the formation of mixed ag-gregate structures consisting ofindividual simple nano-struc-tures [26, 37, 38]. These include,for example, the colloidosomes,particulate core-shell structuresin which the shell is comprised ofindividual or fused nanoparticlessurrounding a liquid or a solidcore. Such systems serve for theprotection of bio-active sub-stances or the targeted release ofbio-active substances, for exam-ple omega-3 fatty acids [39].

Due to their superior stability inrespect of storage and freezing,emulsions with multiple emulsi-fier layers built up utilising thelayer-by-layer principle by thesequential adsorption of differ-ently charged emulsifiers alreadyfind use in the food industry (e.g.deep-frozen ready-made meals,dried soups and sauces in pow-dered form) [27].

Starch-based spherulites arebeing investigated as a new formof carrier systems for biologi-cally active substances. Lipo-somes, on the surface of whichnanogel particles produced bycomplex coacervation are an-chored by electrostatic forces ofattraction, enable vastly bettercontrol over the release of encap-sulated substances [34].

Glossary:milli, micro, nano: These units are, from left to right, one thousandth of the pre-ceding unit: 1 m = 103 mm = 106 m = 109 nm

The traditional classification of nano-structures distinguishes between “puncti-form” (less than 100 nm in all three dimensions, e.g. nanocrystals or emulsions),linear (nano-scaled in two dimensions, e.g. nanofibres, nanotubes and nano-grooves), and layer structures (nano-scaled in only one dimension). Pores can bedescribed as “inverse” nano-structures.*

The exceptional reactivity of nanoparticles results from the extreme surface-to-volume ratio: For a particle with a diameter of 10 nm around 20 % of all atomsor molecules are located on the surface. For a particle with a diameter of 1 nmthis can even be more than 90 %.* The enhanced reactivity is observed up to anorder of magnitude of 300 nm.

The liposomes familiar to the general public for the most part from the cosme-tics and pharmaceutical sectors have sizes between 50 and 1,000 nm and, ac-cording to this definition, therefore are partly above the size for nano-structures.

bleaching earth mono-layers, nano-scaled: also known as betonite mono-lay-ers; betonites have a highly adsorbent and catalytic character.

Immobilisation = here: fixation of enzyme molecules by bonding to a carrier orby incorporation in a (nano-scaled) matrix structure in order to prevent transferto the foodstuff.

CFU: colony forming unit, a measure of the number of bacilli in a sample

amphiphilic: substance which is both hydrophilic and lipophilic, used e. g. as anemulsifier

coacervation: formation of extremely tiny droplet-shaped structures in mixturesof different macro-molecular substances (e. g. proteins)

spherulites: polycrystalline polymer structures with a radially symmetric formand anisotropic character, i. e. with different physical and chemical propertiesalong the different spatial axes

quantum dots: nano-structures which incorporate semiconductor material frac-tions

nanocomposites: solid multi-phase systems in which nano-materials are inte-grated in polymer structures

conductive polymers: electrically conductive plastics

Langmuir-Blodgett films: Layers comprised of one or more single layers of or-ganic material (mostly amphiphilic substances) transferred by immersion in a li-quid from the boundary layer to a solid material

carbon nanotubes: tubular nano-structures. Because of their good conductivityand their affinity for biological molecules these are increasingly employed in thedesign of biosensors [1]. Carbon nanotubes coated with antibodies, capable ofconducting weak electric currents virtually loss-free enable the detection of thebonding of individual molecules, whereby the surface can be quickly regenera-ted with relatively little effort following measurement.

self-assembly: Thermodynamic processes in which a structural or pattern for-mation occurs without external influences as a result of the existing molecular andcolloidal interactions.

*Definition according to: Büro für Technikfolgenabschätzung (2006) TA-Projekt Nanotechnologie.Endbericht. URL: www.tab-beim-bundestag.de/de/pdf/publikationen/berichte/TAB-Arbeitsbericht-ab092.pdf Zugriff 08.01.13



Summary and outlook

Due to their extreme surface-to-volume ratios, many nano-structuresshow very substantial alterations intheir physical and chemical properties.These can alter the functionalityand/or the bioavailability of many in-gredients. For the consumer it is of in-terest that nanotechnology enablesimproved foodstuff safety (for exam-ple by reducing the annual number offood poisoning cases) and can also en-hance the uptake of health-related bi-ologically active substances.

It is important to ensure that allstructures produced are degraded in oreliminated by the body without im-pairment of health. For nano-struc-tures formed from food ingredientsand for which enzyme systems existwhich allow their degradation, ac-cording to assessments to date thereare no serious toxicological reserva-tions. Nevertheless, the alteredbioavailability of encapsulated sub-stances, such as vitamin D3 or A,must be more closely investigated inrespect of their safe use, as an over-dose of these could be injurious tohealth.

At the same time nanomaterials canalso be present in food in natural form[40]. Thus, naturally occurringnanosystems, such as the casein mi-celle, are known which are well suitedfor ensuring the required uptake of vi-tamin D3 in the human body [41].

The application of inorganic nano-structures must be viewed very dif-ferently. Currently, these are the sub-ject of intensive nanotoxicological re-search.

Thus, for example silver and also silversalts are approved within the scope ofadditive approval legislation as E 174for certain applications and can, forexample, be used as a colouring agentfor the “quantum satis“ (in theamount required to achieve the desiredeffect) coating of confectioneries or forthe preservation of drinking water.

However, in accordance with the rele-vant EC regulation (1333/2008) theuse of silver (salts) in the form of silvernanoparticles is not approved, as anadditive produced by nanotechnologyis regarded as a new additive and istherefore subject to the regulationconcerning novel foods and novelfood ingredients (EC 258/97), whichregulates the obligation to obtain ap-proval for foodstuffs with nanomate-rials in the EU.

Silver nanoparticles are neverthelessalready in use as anti-microbial sub-stances in surface coatings, for exam-ple in refrigerators or in packagingmaterials (nanoclay).

The German Federal Office for Risk As-sessment (BfR) recommends that pro-ducers do not employ nano-scaled sil-ver or nano-scaled silver compoundsin foodstuffs and products for dailyuse until the available data allow afinal assessment of health risks andthe use of these products is known tobe safe.

Grounds: Studies have shown that thebactericidal effect of nano-scaled silverdepends upon the concentration, theform (spherical, rod-shaped, cubic orfilamentous, irregular, or nanofilm)and can also greatly vary according tothe surface reactivity [42]. Naturalbarriers, such as the intestinal mu-cosa, can also be more easily passed,so that silver could enter the blood-stream and be distributed over differ-ent organs. Furthermore, bacterial re-sistance can be expected with the useof silver nanoparticles [43].

Currently partly nano-scaled systemsare mostly employed as excipients, forexample as a secondary product oflarger silicon dioxide aggregates usedto ensure the free flow and trickling ofingredients in powder form. Organicnanoparticles are also employed in theform of micelles for the solubilisationof ethereal oils (spice extracts), en-abling their use as anti-oxidative sub-

stances incorporated in sausage prod-ucts or ready-made meals. These pre-vent oxidative alterations, such asrancidness.

In the food sector more intensive in-vestigations of the digestion of nano-structured foodstuff components arerequired. In relation to new legislationcurrently being formulated in Europeand the USA, this would be entirelywelcome. The role of food technolo-gists during product developmentshould be to consider toxicologicaltesting early on in order to achieve abetter balance between benefits, costsand risks for the new materials andstructures.

Prof. Dr. Jochen WeissDr. Monika GibisFachgebiet für Lebensmittelphysik undFleischwissenschaftInstitut für Lebensmittelwissenschaft undBiotechnologieUniversität HohenheimGarbenstr. 25, 70599 StuttgartE-Mail: [email protected]

Conflict of interest:Professor Weiss is a member of the board of directors of the association FoodDACH e. V. for the networking of research and industry inGermany, Austria and Switzerland.

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DOI: 10.4455/eu.2013.011

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