Contents Digest Trends in Food Science & Technology 37 (2014) 1e4

Milk proteins asencapsulation devicesand delivery vehicles

Increasing the shelf life of sensitivesubstances and targeting the release ofnutritional/bioactive molecules areamong the great challenges for thefood industry. The development offood products with embedded encapsu-lation devices used to reach these ob-jectives constitutes a growing market.Milk proteins are biopolymers that arechemically and structurally versatileand are well adapted to several encap-sulation purposes. On page 5, Sa€ıdBouhallab and coworkers review thestrategies, techniques, advantages andtrends associated with the use of milkproteins as encapsulating device arereviewed. Special attention is given tothe novel potential of reversibly co-assembled protein structures as encap-sulating devices. Encapsulation tech-nologies that have been used for along time in the pharmaceutical indus-try for drug delivery applications offera real opportunity for the food industry.Encapsulation represents a means todevelop innovative products to satisfythe growing demand of the consumerfor foods with health and well-beingbenefits and is now widely used to sta-bilize food ingredients, increase flavorretention or to mask undesirable fla-vors. Hydrophobic vitamins, polyphe-nols, flavorings, fatty acids, cells, andminerals are among encapsulated bio-actives. At the laboratory scale, milkproteins are effective in protectingbioactives against oxidation and photo-degradation, increasing their solubility,and in maintaining the viability of pro-biotic cells. Traditional encapsulationstechnologies have been applied tomilk proteins, including spray drying,freeze drying, extrusion and coacerva-tion. However, despite the success ona laboratory scale, these technologiesapplied to proteins as encapsulationdevices still present limitations and

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difficulties for the large-scale produc-tion of food-grade microencapsulatedsubstances. Hence, the up scaling oflaboratory results remains a researchchallenge. For food applications, afurther challenge is to ensure that sensi-tive molecules can be entrapped in aform that is physically and chemicallycompatible with the food matrixwithout adverse effects. Also, the useof milk proteins for the targeted deliv-ery of food bioactives or for increasingnutrient bioavailability remains anemerging research area. Encapsulationvia novel technologies constitutesanother issue for future research. Thetrend is toward a reduction in particlesize with a special interest in devel-oping techniques such as electrospray-ing and electrospinning of proteins forthe production of nanosized particles.Another field to explore is the encapsu-lating potentialities of spontaneouslyco- or self-assembled supra-molecularstructures: native casein micelles, a-lactalbumin nanotubes, b-lactoglobulinfibers, and nanospheres from oppositelycharged proteins. The fact that thesenanoparticles are tailored from naturaland edible polymers, without the useof exogenous additives, makes thempromising as building blocks for encap-sulation, offering several associatedinnovations and advantages. Beforesuggested applications are imple-mented, fundamental research to bettercontrol milk protein co-assembly intonano-microspheres is needed in partic-ular concerning: (i) assembly and disas-sembly mechanisms in the presence ofbioactives and (ii) the stability offormed supra-molecular structures to-ward processing and storage conditionseither on their own or incorporatedwithin food matrices. For some applica-tion purposes, it would be necessary totailor and stabilize these structures us-ing, for instance, food-grade cross-linkers. Due to their edibility, milk pro-teins and their multiple assembliesconstitute ideal drug carriers for anoral-delivery system and several phar-maceutical projects are alreadyongoing.

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Melatonin from differentfruit sources, functionalroles, and analyticalmethods

Recently melatonin has been reportedin different fruits and its exact amountis influenced by many factors,including fruit type, variety andripening stage, growth location andcondition, and analytical method em-ployed. Validated analytical methodswith adequate sample treatment arerequired to obtain accurate measure-ment of melatonin in fruits. Impor-tantly, diet high in melatonin fromfruits could enhance human health.Also, melatonin could be used toimprove the phytoremediation effi-ciency of plants against different pollut-ants such as heavy metals. On page 21,Xiaoyuan Feng and coworkers reviewthe recent contributing factors on theproduction and amount of melatoninin fruits, current analytical approaches,its functional roles, as well as the futureresearch needs to clarify the mecha-nisms of fruit melatonin for improvinghuman health and environment contam-inations. Melatonin is a compoundnaturally present in foods. It has beenshown that melatonin is widespread indifferent varieties of fruit and its exactamount is influenced by many factors,including fruit varieties and ripenessstage, genetic traits, growth conditions,environmental stresses, and analyticalmethod. Recently more studies havefocused on understanding the relation-ships between melatonin content andfruit ripening stage, but the regulatedmechanisms of melatonin based onthe fruit ripening have not been fullyunderstood. Noticeably, the influenceof postharvest manipulations to prolongthe shelf life of fruits on melatonin con-centrations has not been investigatedyet. Such information may help the un-derstanding of the physiological rolesof melatonin during ripening. To accu-rately determine the amount of mela-tonin in fruits, validated analytical

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methods with adequate sample treat-ment are required, which remains themost challenging in the study of mela-tonin in fruits. There is a need formore accurate analytical methods toobtain reliable result in fruits in orderto compile data to understand theimpact of the dietary melatonin. Thebiosynthetic pathway of melatonin infruits should also be further studied aswell, although the recent research veri-fied the presence of SNAT in plants forthe first time and ASMT is the rate-limiting enzyme for melatonin biosyn-thesis. It is unclear whether the postu-lated biosynthetic pathway in plants isubiquitous or not. The homologue or aparalogue of 5-OH Trp synthase hasnot been identified in plants, implyingthat the enzyme, that converts trypto-phan to serotonin, may have a differentevolutionary origin. Moreover, studiesindicated that the primary function ofmelatonin in fruits is to serve as thefirst line of defense against oxidativestresses, which are a result of internaland environmental insults. However, itis still unknown whether the antioxi-dant capacity of melatonin in fruits isexclusively dependent on its directinteraction with ROS or it is mediatedby melatonin receptors. Melatonin re-ceptors have not been reported in fruits.Besides functioning as an antioxidant,melatonin could be used to improve thephytoremediation efficiency of plantsagainst different pollutants such as heavymetals. Finally, fruit intake may influ-ence endogenous melatonin level andconsequently promote human health byvirtue of its biological activities. Hence,the use of melatonin in nutraceuticaland environment phytoremediation is anew frontier to be explored.

Role of processing onbioaccessibility ofminerals

Phytate, phenolic compounds and fiberare known anti-nutritional factors

(ANFs) that contribute to the low bio-accessibility and bioavailability of ironand zinc in plant foods. Better insightinto the localization of minerals andanti-nutritional factors in plant tissues,as well as on the mechanisms of inter-action between minerals and ANFs,may lead to better targeted processingfor improvement of the bioaccessibilityof minerals in plant foods. On page 32,John Van Camp and coworkers reviewthe subcellular distribution of iron andzinc and their ANFs in plant organs,as well as the mechanisms of interac-tion between these metals and theirANFs. These insights are then used tobetter clarify the role of various pro-cessing technologies, like mechanicaltreatments, soaking, germination,fermentation and heating, on improvingthe bioaccessibility of iron and zinc inplant foods. It is clear that an increasein mineral bioaccessibility cannot beobtained by focusing on the complexa-tion and/or degradation of just oneANF. Therefore, more knowledge isneeded on how different ANFs acttogether in determining the mineralbioaccessibility in plant products. Be-sides, it is important to take into ac-count the cellular location of bothminerals and ANFs when investigatingthe impact of different processingtechniques on the increase of mineralbioaccessibility. New techniquesincluding high resolution secondaryion mass spectrometry (NanoSIMS),synchrotron radiation soft X-ray full-field imaging mode (FFIM) and low-energy X-ray fluorescence (LEXRF)spectromicroscopy are now availableto study the mineral and antinutrientlocation and interaction in the plantbefore and after processing, and thusmore insight can be gained. Based onthe various interaction mechanisms,relevant processing techniques can beselected, i.e. destroying the plant ma-trix, and thus affecting the location inthe plant cell of both minerals andANFs, influencing the pH, which inturn affects the interaction, and degra-dation or conversion of ANFs (phytate,phenolic compounds and fibers), all ofthem affecting the bioaccessibility.However, one needs to take into

account that interaction of mineralswith other compounds (e.g. proteins,fermentation metabolites) can alsooccur, which in turn, can affect the min-eral bioaccessibility.

Protein nanostructures infood e should we beworried?

Nanotechnology promises to affectmany aspects of our lives with itsdevelopment being greeted with bothexcitement and fear. The debate con-cerning nanotechnology has echoedthat of genetically engineered organ-isms and their introduction into theenvironment and the food chain. Nano-technology offers many potential ad-vantages in the processing andmanufacture of foods: enhancedbioavailability, color and flavor; novelfood textures; new delivery mecha-nisms; and access to biosensors toenhance food safety. In fact, many ofthe foods we have been consuming forcenturies already contain nanostruc-tures, leading many to assume thatthey are safe. The extent to which novelnanostructures may afford new riskshas not been adequately resolved, how-ever, leading to concern within someconsumer groups. In this article, weuse proteins as a case study to exploreour current understanding of nanostruc-tures in foods and the extent to whichnovel nanostructures may introducenew properties. It is well recognizedthat some protein nanostructures aretoxic and are associated with disease,so there is legitimate concern as towhether such species should be deliber-ately introduced into our foods. Onpage 42, Juliet A. Gerrard and co-workers review current literature onprotein nanostructures in food andpossible risks associated with theiruse, and aim to provide a balancedassessment to inform future decision-making regarding the utilization of

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nanostructures in food. The studies re-viewed here suggest we should proceedwith caution when considering thedevelopment of new nanostructuresfor use in food, especially amyloid fi-brils. This view is consistent with theUK Lords Science and TechnologyCommittee, which has also called forcaution, suggesting further discussionand the establishment of a list ofcommercially available products con-taining nanomaterials maintained byfood agencies along with more trans-parency in the industry. Internationally,there is much interest among food reg-ulatory bodies, with reviews and multi-lateral discussions currently underwayin bodies such as Food StandardsAustralia and New Zealand, the USFood and Drug Administration, Euro-pean Food Safety Authority and HealthCanada. These reviews are likely tolead to new guidelines and regulationsfor both novel food ingredients andpackaging. Advances in this field relyon studies that aim to improve ourfundamental understanding of nano-technology in food, from the toolsused to assess and characterize struc-tures in food to the methods used toassess potential toxicity. Key issuesinclude the interactions between nano-structures and the food matrix, as wellas the absorption, digestibility andpersistence of nanomaterials. Reportsreleased by the European Food SafetyAuthority (EFSA) in 2009 and 2011provide valuable insight into how therisks of amyloid fibrils may be assessedby regulators. Where information isavailable on the non-nanoform of theingredient, it is suggested comparisonsbe made between the nanoform andnon-nanoform. Where there is no infor-mation on the non-nanoform, moredetailed testing is required. It is impor-tant that both the structure and size ofthe material are considered, as amyloidfibrils are an example of how structureswith identical composition can differ intheir toxicity. The 2011 EFSA reportalso suggests that food or packagingwith complex morphology, such aslong tubes and fibers should be testedfor possible toxicity. Toxicity tests rec-ommended by the EFSA include in vivo

genotoxicity tests, absorption, distribu-tion, metabolism and excretion(ADME) tests, repeated-dose 90-dayoral toxicity studies in rodents,in vitro digestion studies and a rangeof other detailed tests depending onthe food type and exposure scenario.Additional tests relevant to amyloid fi-brils could include studies of cellularuptake and conversion of cellular pro-teins to an aggregated or fibrillarform, similar to tests used to assessthe toxicity of disease-associated pro-teins. In the U.S., the Food and DrugAdministration (FDA) has just releaseddraft legislation on this issue withguidelines currently available for indus-try stating that there is a “critical needto learn more about the potential roleand importance of dimensions in thecharacteristics exhibited by engineerednanomaterials that may be used in pro-ducing products regulated by FDA”.From the above discussion, it is clearthat more research in this growingarea is urgently needed.

New trends intechnology and identityof traditional dairy andfermented meatproduction processes

Interest in ecofood tourism is strictlyrelated to the consumption of productsassociated with the geographical areavisited. Local products are often re-quested by consumers living far fromthe production zones (e.g. in bistrorestaurants that reproduce the atmo-sphere of typicality). This phenome-non, if on the one hand guaranteeingthe continued popularity of certaintraditional foods the inherent dangerthat certain types of foods pose couldalso spread the risks to a much widerarea that it might typically inhabit.Higher the demand for certain products,more the variations of the productionprocesses of the traditional products.

This is particularly evident for fer-mented products that do not have trade-mark protection, which allows productsmade with different technologies and/orraw materials to use the same designa-tion. On page 51, Luca Settanni andGiancarlo Moschetti review reportsthe strengths and the weaknesses oftraditional fermented food products,examining the concept of typicality,and evidencing the risks associatedwith consumption. Traditional foodproduction processes are an integralpart of regional culture. The consump-tion of typical foods strengthens con-nections with the places of theirorigin, helping preserve their way oflife and their future development. Forfermented foods in particular, a changein production technology is sometimesnecessary in order to ensure consumers’safety and to foster the perception thatthe foods are natural. However, thechanges must be respectful of traditionin order to avoid an irreversible rejec-tion by consumers. Since trust is earnedover time and generations, one wrongact can affect the entire system ofproduction for a given food. Theautochthonous microbiota, consideredas local raw material/ingredient, mayplay a major role in the determinationof territorial specificity because theycould make the food safer to eat andalso, in many ways, help to preservethe identity of the typical, traditionalfoods. Fermented foods made fromraw milk or meat must be manufacturedwith the addition of autochthonous mi-croorganisms not only for the preserva-tion of food typicality, but also foravoiding risks to consumers’ health.

Complex interfaces infood: structure andmechanical properties

Multiphase food systems (emulsions,foam) often have interfaces with acomplex microstructure, formed by

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interfacial self-assembly of proteins,lipids, or colloidal particles. Theresponse of these interfaces to deforma-tions tends to be highly nonlinear and farmore complex than the response of in-terfaces stabilized by simple low molec-ular weight surfactants. On page 59,Leonard M.C. Sagis and Elke Scholtenreview various types of complex inter-faces encountered in food products,and discuss their microstructure andme-chanical properties. They also discusshow to properly characterize thenonlinear behavior of these interfaces,using surface rheological techniques,droplet deformation studies, and struc-tural characterization methods. Severaltypes of microstructures observable incomplex fluidefluid interfaces havebeen reviewed in food systems. We

have discussed some of the dynamicproperties of these interfaces, and re-viewed experimental methods, whichcan be used to explore the often highlynonlinear response of these interfacesto deformation, temperature, and con-centration gradients. We believe thatthe most efficient approach to developand characterize highly stable emul-sions, foam, or encapsulation systems,is a multiscale approach that closely in-tegrates experimental, theoretical, andcomputational methods. In all of thesefields further developments are neededbefore we can treat real food systems,but current developments in these fieldsare promising, and a comprehensivemodeling of complex interfaces on allof their relevant length scales is withinreach. In the experimental field there is

a particular need for advances in struc-tural evaluation methods, which can becombined with (preferably simulta-neous) surface shear or dilatational mea-surements (2d rheooptic). In the field oftheoretical constitutive modeling aconsiderable effort is needed to generatenew nonlinear constitutive models,capturing the link between time evolu-tion of an interface’s microstructureand its rheological response. Currentlystill very few models of that nature areavailable. Finally, in the field of multi-phase computational methods there is adefinite need for solvers, which canhandle the aforementioned nonlinearconstitutive models, on arbitrarilyshaped and arbitrarily deforminginterfaces.