Methods for Stability Studies

  • Maria Lidia Herrera
Part of the SpringerBriefs in Food, Health, and Nutrition book series (BRIEFSFOOD, volume 3)


The efficient development and production of high-quality emulsion-based products depend on knowledge of their physicochemical properties and stability. A wide variety of different analytical techniques and methodologies have been developed to characterize the properties of food emulsions. Analytical instruments and experimental methodologies are needed for research and development purposes to elucidate the relationship between droplet characteristics and the bulk physicochemical and sensory properties of food emulsions, such as stability, texture, flavor, and appearance. They are also needed in quality control laboratories and in food production factories to monitor food emulsions and their components before, during, and after production so as to ensure that their properties conform to predefined quality criteria and/or to predict how the final product will behave during storage. This chapter describes the most commonly used methods for stability studies, with a focus on conventional food emulsions. Some of these techniques are also used in nanoemulsions. Several examples of applications are described in detail.


Droplet Size Whey Protein Emulsion Stability Solid Lipid Nanoparticle Emulsion Droplet 
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  1. Acero Lopez A, Corredig M, Alexander M (2009) Diffusing wave and ultrasonic spectroscopy of rennet-induced gelation of milk in the presence of high-methoxyl pectin. Food Biophys 4:249–259CrossRefGoogle Scholar
  2. Acero Lopez A, Alexander M, Corredig M (2010) Diffusing wave spectroscopy and rheological studies of rennet-induced gelation of skim milk in the presence of pectin and κ-carrageenan. Int Dairy J 20:328–335CrossRefGoogle Scholar
  3. Alexander M, Dalgleish DG (2006) Dynamic light scattering techniques and their applications in food science. Food Biophys 1:2–13CrossRefGoogle Scholar
  4. Alvarez Cerimedo MS, Huch Iriart C, Candal RJ, Herrera ML (2010) Stability of emulsions formulated with high concentrations of sodium caseinate and trehalose. Food Res Int 43:1482–1493CrossRefGoogle Scholar
  5. Bazmi A, Relkin P (2006) Thermal transitions and fat droplet stability in ice cream mix model systems. Effect of milk fat fractions. J Therm Anal Calorim 84:99–104CrossRefGoogle Scholar
  6. Beattie JK, Djerdjev A (2000) Rapid electroacoustic method for monitoring dispersion: zeta potential titration of alumina with ammonium poly(methacrylate). J Am Ceram Soc 83:2360–2364CrossRefGoogle Scholar
  7. Berg T, Arlt P, Brummer R, Emeis D, Kulicke WM, Wiesner S, Wittern KP (2004) Insights into the structure and dynamics of complex W/O-emulsions by combining NMR, rheology and electron microscopy. Colloids Surf A Physicochem Eng Asp 238:59–69CrossRefGoogle Scholar
  8. Berli CLA, Quemada D, Parker A (2002) Modelling the viscosity of depletion flocculated emulsions. Colloids Surf A Physicochem Eng Asp 203:11–20CrossRefGoogle Scholar
  9. Binks BP, Desforges A, Duff DG (2007) Synergistic stabilization of emulsions by a mixture of surface-active nanoparticles and surfactant. Langmuir 23:1098–1106CrossRefGoogle Scholar
  10. Blonk JCG, Van Aalst H (1993) Confocal scanning light microscopy in food research. Food Res Int 26:297–311CrossRefGoogle Scholar
  11. Bonnet C, Corredig M, Alexander M (2005) Stabilization of caseinate-covered oil droplets during acidification with high methoxyl pectin. J Agric Food Chem 53:8600–8606CrossRefGoogle Scholar
  12. Bordes C, Snabre P, Frances C, Biscans B (2003) Optical investigation of shear- and time-dependent microstructural changes to stabilized and depletion-flocculated concentrated latex sphere suspensions. Powder Technol 130:331–337CrossRefGoogle Scholar
  13. Boyd BJ, Rizwan SB, Dong YD, Hook S, Rades T (2007) Self-assembled geometric liquid-crystalline nanoparticles imaged in three dimensions: hexosomes are not necessarily flat hexagonal prisms. Langmuir 23:12461–12464CrossRefGoogle Scholar
  14. Buron H, Mengual O, Meunier G, Cayre I, Snabre P (2004) Optical characterization of concentrated dispersions: applications to laboratory analyses and on-line process monitoring and control. Polym Int 53:1205–1209CrossRefGoogle Scholar
  15. Cabezas DM, Madoery R, Diehl BWK, Tomas MC (2011) Emulsifying properties of different modified sunflower lecithins. J Am Oil Chem Soc. doi: 10.1007/s11746-011-1915-8
  16. Chanamai R, Coupland JN, McClements DJ (1998) Effect of temperature on the ultrasonic properties of oil-in-water emulsions. Colloids Surf A Physicochem Eng Asp 139:241–250CrossRefGoogle Scholar
  17. Chappellaz A, Alexander M, Corredig M (2010) Phase separation behavior of caseins in milk containing flaxseed gum and κ-carrageenan: a light-scattering and ultrasonic spectroscopy study. Food Biophys 5:138–147CrossRefGoogle Scholar
  18. Chauvierre C, Labarre D, Couvreur P, Vauthier C (2004) A new approach for the characterization of insoluble amphiphilic copolymers based on their emulsifying properties. Colloids Polym Sci 282:1097–1104CrossRefGoogle Scholar
  19. Chen J, Vogel R, Werner S, Heinrich G, Clausse D, Dutschk V (2011) Influence of the particle type on the rheological behavior of Pickering emulsions. Colloids Surf A Physicochem Eng Asp 382:238–245CrossRefGoogle Scholar
  20. Chhabra RP, Agarwal S, Chaudhary K (2003) A note on wall effect on the terminal falling velocity of a sphere in quiescent Newtonian media in cylindrical tubes. Powder Technol 19:53–58CrossRefGoogle Scholar
  21. Cho YH, McClements DJ (2007) In situ electroacoustic monitoring of polyelectrolyte adsorption onto protein-coated oil droplets. Langmuir 23:3932–3936CrossRefGoogle Scholar
  22. Corredig M, Alexander M (2008) Food emulsions studied by DWS: recent advances. Trends Food Sci Technol 19:67–75CrossRefGoogle Scholar
  23. Corredig M, Alexander M, Dalgleish DG (2004a) The application of ultrasonic spectroscopy to the study of the gelation of milk components. Food Res Int 37:557–565CrossRefGoogle Scholar
  24. Corredig M, Verespej E, Dalgleish DG (2004b) Heat-induced changes in the ultrasonic properties of whey proteins. J Agric Food Chem 52:4465–4471CrossRefGoogle Scholar
  25. Dalgleish DG, Spagnuolo PA, Goff DG (2004) A possible structure of the casein micelle based on high-resolution field-emission scanning electron microscopy. Int Dairy J 14:1025–1031CrossRefGoogle Scholar
  26. Dalgleish DG, Verespej E, Alexander M, Corredig M (2005) The ultrasonic properties of skim milk related to the release of calcium from casein micelles during acidification. Int Dairy J 15:1105–1112CrossRefGoogle Scholar
  27. de Castro SR, Kawazoe Sato AC, Lopes da Cunha R (2012) Emulsions stabilized by heat-treated collagen fibers. Food Hydrocolloid 26:73–81CrossRefGoogle Scholar
  28. Dickinson E (1995) Emulsion stabilization by polysaccharides and protein-polysaccharide complexes. In: Stephen AM (ed) Food polysaccharides and their applications. Marcel Dekker, New York, pp 501–515Google Scholar
  29. Dickinson E (1998) Proteins at interfaces and in emulsions: stability, rheology and interactions. J Chem Soc Faraday Trans 94:1657–1669CrossRefGoogle Scholar
  30. Dickinson E (1999) Caseins in emulsions: interfacial properties and interactions. Int Dairy J 9:305–312CrossRefGoogle Scholar
  31. Dickinson E (2003) Hydrocolloids at interfaces and the influence on the properties of dispersed systems. Food Hydrocolloids 17:25–39CrossRefGoogle Scholar
  32. Dickinson E, Golding M (1997a) Rheology of sodium caseinate stabilized oil-in-water emulsions. J Colloid Interface Sci 191:166–176CrossRefGoogle Scholar
  33. Dickinson E, Golding M (1997b) Depletion flocculation of emulsions containing unadsorbed sodium caseinate. Food Hydrocolloids 11:13–18CrossRefGoogle Scholar
  34. Dickinson E, Golding M, Povey MJW (1997) Creaming and flocculation of oil-in-water emulsions containing sodium caseinate. J Colloid Interface Sci 185:515–529CrossRefGoogle Scholar
  35. Dissanayeke M, Vasiljevic T (2009) Functional properties of whey proteins affected by heat treatment and hydrodynamic high-pressure shearing. J Dairy Sci 92:1387–1397CrossRefGoogle Scholar
  36. Dukhin AS, Goetz PJ, Fang X, Somasundaran P (2010) Monitoring nanoparticles in the presence of larger particles in liquids using acoustics and electron microscopy. J Colloid Interface Sci 342:18–25CrossRefGoogle Scholar
  37. Dwyer C, Donnelly L, Buckin V (2005) Ultrasonic analysis of rennet-induced pre-gelation and gelation processes in milk. J Dairy Res 72:303–310CrossRefGoogle Scholar
  38. Fox PF, Brodkorb A (2008) The casein micelle: historical aspects, current concepts and significance. Int Dairy J 18:677–684CrossRefGoogle Scholar
  39. Gancz K, Alexander M, Corredig M (2005) Interactions of high methoxyl pectin with whey proteins at oil/water interfaces at acid pH. J Agric Food Chem 53:2236–2241CrossRefGoogle Scholar
  40. Gaygadzhiev Z, Alexander M, Corredig M (2009) Sodium caseinate-stabilized fat globules inhibition of the rennet-induced gelation of casein micelles studied by diffusing wave spectroscopy. Food Hydrocolloids 23:1134–1138CrossRefGoogle Scholar
  41. Ghosh S, Rousseau D (2009) Freeze-thaw stability of water-in-oil emulsions. J Colloid Interface Sci 339:91–102CrossRefGoogle Scholar
  42. Gulseren İ, Corredig M (2011) Changes in colloidal properties of oil in water emulsions stabilized with sodium caseinate observed by acoustic and electroacoustic spectroscopy. Food Biophys 6:534–542CrossRefGoogle Scholar
  43. Gulseren İ, Alexander M, Corredig M (2010) Probing the colloidal properties of skim milk using acoustic and electroacoustic spectroscopy. Effect of concentration, heating and acidification. J Colloid Interface Sci 351:493–500CrossRefGoogle Scholar
  44. Heertje I, Vandervlist P, Blonk JCG, Hendrickx H, Brakenhoff GJ (1987) Confocal scanning laser microscopy in food research—some observations. Food Microstruct 6:115–120Google Scholar
  45. Herrera ML, Hartel RW (2001) Unit D 3.2.1–6 lipid crystalline characterization, basic protocole. In: Current protocols in food analytical chemistry (CPFA), vol I. Wiley, New York. ISBN 0-471-32565-1Google Scholar
  46. Herrera M, de Leon GM, Hartel RW (1999) A kinetic analysis of crystallization of a milk fat model system. Food Res Int 32:289–298CrossRefGoogle Scholar
  47. Hiemenz PC, Rajagopalan R (1997) Electrostatic and polymer-induced colloid stability. In: Principles of colloid and surface chemistry, 3rd edn. Marcel Dekker, New York, pp 575–624Google Scholar
  48. Jena S, Das H (2006) Modeling of particle size distribution of sonicated coconut milk emulsion: effect of emulsifiers and sonication time. Food Res Int 39:606–611CrossRefGoogle Scholar
  49. Jirapeangtong K, Siriwatanayothin S, Chiewchan N (2008) Effects of coconut sugar and stabilizing agents on stability and apparent viscosity of high-fat coconut milk. J Food Eng 87:422–427CrossRefGoogle Scholar
  50. Jourdain L, Leser ME, Schmitt C, Michel M, Dickinson E (2008) Stability of emulsions containing sodium caseinate and dextran sulfate: relationship to complexation in solution. Food Hydrocolloids 22:647–659CrossRefGoogle Scholar
  51. Juliano P, Kutter A, Cheng LJ, Swiergon P, Mawson R, Augustin MA (2011) Enhanced creaming of milk fat globules in milk emulsions by the application of ultrasound and detection by means of optical methods. Ultrason Sonochem 18:963–973CrossRefGoogle Scholar
  52. Kalnin D, Ouattara M, Ollivon M (2004) A new method for the determination of the concentration of free and associated sodium caseinate in model emulsions. Prog Colloid Polym Sci 128:207–211Google Scholar
  53. Karunasawat K, Anprung P (2010) Effect of depolymerized mango pulp as a stabilizer in oil-in-water emulsion containing sodium caseinate. Food Bioprod Process 88:202–208CrossRefGoogle Scholar
  54. Keowmaneechai E, McClements DJ (2002) Influence of EDTA and citrate on physicochemical properties of whey protein-stabilized oil-in-water emulsions containing CaCl2. J Agric Food Chem 50:7145–7153CrossRefGoogle Scholar
  55. Khalloufi S, Alexander M, Goff HD, Corredig M (2008) Physicochemical properties of whey protein isolate stabilized oil-in-water emulsions when mixed with flaxseed gum at neutral pH. Food Res Int 41:964–972CrossRefGoogle Scholar
  56. Kiokias S, Reiffers-Magnani CK, Bot A (2004a) Stability of whey-protein-stabilized oil-in-water emulsions during chilled storage and temperature cycling. J Agric Food Chem 52:3823–3830CrossRefGoogle Scholar
  57. Kiokias S, Reszka AA, Bot A (2004b) The use of static light scattering and pulsed-field gradient NMR to measure droplet sizes in heat-treated acidified protein-stabilised oil-in-water emulsion gels. Int Dairy J 14:287–295CrossRefGoogle Scholar
  58. Konya M, Dekany I, Eros I (2007) X-ray investigation of the role of the mixed emulsifier in the structure formation in o/w creams. Colloid Polym Sci 285:657–663CrossRefGoogle Scholar
  59. Lemarchand C, Couvreur P, Besnard M, Costantini D, Gref R (2003) Novel polyester-polysaccharide nanoparticles. Pharm Res 20:1284–1292CrossRefGoogle Scholar
  60. Liu F, Tang CH (2011) Cold, gel-like whey protein emulsions by microfluidisation emulsification: rheological properties and microstructures. Food Chem 127:1641–1647CrossRefGoogle Scholar
  61. Liu J, Alexander M, Verespej E, Corredig M (2007a) Real-time determination of structural changes of sodium caseinate-stabilized emulsions containing pectin using high resolution ultrasonic spectroscopy. Food Biophys 2:67–75CrossRefGoogle Scholar
  62. Liu J, Corredig M, Alexander M (2007b) A diffusing wave spectroscopy study of the dynamics of interactions between high methoxyl pectin and sodium caseinate emulsions during acidification. Colloids Surf B Biointerfaces 59:164–170CrossRefGoogle Scholar
  63. Liu J, Verespej E, Alexander M, Corredig M (2007c) Comparison on the effect of high-methoxyl pectin or soybean soluble polysaccharide on the stability of sodium caseinate-stabilized oil/water emulsions. J Agric Food Chem 55:6270–6278CrossRefGoogle Scholar
  64. Liu J, Verespej E, Corredig M, Alexander M (2008) Investigation of interactions between two different polysaccharides with sodium caseinate-stabilized emulsions using complementary spectroscopic techniques: diffusing wave and ultrasonic spectroscopy. Food Hydrocolloids 22:47–55CrossRefGoogle Scholar
  65. Macierzanka A, Szeląg H (2006) Microstructural behavior of water-in-oil emulsions stabilized by fatty acid esters of propylene glycol and zinc fatty acid salts. Colloids Surf A Physicochem Eng Asp 281:125–137CrossRefGoogle Scholar
  66. Maldonado-Valderrama J, Rodriguez Patino JM (2010) Interfacial rheology of protein-surfactant mixtures. Curr Opin Colloid Interface Sci 15:271–282CrossRefGoogle Scholar
  67. Manoi K, Rizvi SSH (2008) Rheological characterizations of texturized whey protein concentrate-based powders produced by reactive supercritical fluid extrusion. Food Res Int 41:786–796CrossRefGoogle Scholar
  68. Manoi K, Rizvi SSH (2009) Emulsification mechanisms and characterizations of cold, gel-like emulsions produced from texturized whey protein concentrate. Food Hydrocolloids 23:1837–1847CrossRefGoogle Scholar
  69. Marangoni AG, Hartel RW (1998) Visualization and structural analysis of fat crystal networks. Food Technol 52:46–51Google Scholar
  70. Matsumiya K, Nakanishi K, Matsumura Y (2011) Destabilization of protein-based emulsions by diglycerol esters of fatty acids—the importance of chain length similarity between dispersed oil molecules and fatty acid residues of the emulsifier. Food Hydrocolloids 25:773–780CrossRefGoogle Scholar
  71. McClements DJ (1999) Emulsion rheology. In: Food emulsions principles, practice and techniques. CRC Press, Washington, DC, pp 235–266Google Scholar
  72. McClements DJ (2007) Critical review of techniques and methodologies for characterization of emulsion stability. Crit Rev Food Sci Nutr 47:611–649CrossRefGoogle Scholar
  73. McClements DJ, Coupland JN (1996) Theory of droplet size distribution measurements in emulsions using ultrasonic spectroscopy. Colloids Surf A Physicochem Eng Asp 117:161–170CrossRefGoogle Scholar
  74. Medina-Torres L, Calderas F, Gallegos-Infante JA, Gonzalez-Laredo RF, Rocha-Guzman N (2009) Stability of alcoholic emulsions containing different caseinates as a function of temperature and storage time. Colloids Surf A Physicochem Eng Asp 352:38–46CrossRefGoogle Scholar
  75. Mengual O, Meunier G, Cayre I, Puech K, Snabre P (1999) Turbiscan MA 2000: multiple light scattering measurement for concentrated emulsion and suspension instability analysis. Talanta 50:445–456CrossRefGoogle Scholar
  76. Moschakis T, Murray BS, Biliaderis CG (2010) Modifications in stability and structure of whey protein-coated o/w emulsions by interacting chitosan and gum arabic mixed dispersions. Food Hydrocolloids 24:8–17CrossRefGoogle Scholar
  77. Mun S, Cho Y, Decker EA, McClements DJ (2008) Utilization of polysaccharide coatings to improve freeze-thaw and freeze-dry stability of protein-coated lipid droplets. J Food Eng 86:508–518CrossRefGoogle Scholar
  78. Murray BS (2011) Rheological properties of protein films. Curr Opin Colloid Interface Sci 16:27–35CrossRefGoogle Scholar
  79. Nambam JS, Philip J (2012) Competitive adsorption of polymer and surfactant at a liquid droplet interface and its effect on flocculation of emulsion. J Colloid Interface Sci 366:88–95CrossRefGoogle Scholar
  80. Opawale FO, Burgess DJ (1998) Influence of interfacial properties of lipophilic surfactants on water- in-oil emulsion stability. J Colloid Interface Sci 197:142–150CrossRefGoogle Scholar
  81. Palazolo GG, Sorgentini DA, Wagner JR (2005) Coalescence and flocculation in o/w emulsions of native and denatured whey soy proteins in comparison with soy protein isolates. Food Hydrocolloids 19:595–604CrossRefGoogle Scholar
  82. Pan LG, Tomas MC, Anon MC (2002) Effect of sunflower lecithins on the stability of water-in-oil and oil-in-water emulsions. J Surfact Deterg 5:135–143CrossRefGoogle Scholar
  83. Pinfield VJ, Povey MJW, Dickinson E (1995) The application of modified forms of the Urick equation to the interpretation of ultrasound velocity in scattering systems. Ultrasonics 33:243–251CrossRefGoogle Scholar
  84. Pizzino A, Catte M, Van Hecke E, Salager JL, Aubry JM (2009) On-line light backscattering tracking of the transitional phase inversion of emulsions. Colloids Surf A Physicochem Eng Asp 338:148–154CrossRefGoogle Scholar
  85. Plucknett KP, Pomfret SJ, Normand V, Ferdinando D, Veerman C, Frith WJ, Norton IT (2001) Dynamic experimentation on the confocal laser scanning microscope: application to soft-solid, composite food materials. J Microsc 201:279–290CrossRefGoogle Scholar
  86. Relkin P, Sourdet S (2005) Factors affecting fat droplet aggregation in whipped frozen protein-stabilized emulsions. Food Hydrocolloids 19:503–511CrossRefGoogle Scholar
  87. Rosner S, Shalev DE, Shames AI, Ottaviani MF, Aserina A, Garti N (2010) Do food microemulsions and dietary mixed micelles interact? Colloids Surf B Biointerfaces 77:22–30CrossRefGoogle Scholar
  88. Ruis HGM, Venema P, van der Linden E (2008) Diffusing wave spectroscopy used to study the influence of shear on aggregation. Langmuir 24:7117–7123CrossRefGoogle Scholar
  89. Schokker EP, Dalgleish DG (1998) The shear-induced destabilization of oil-in-water emulsions using caseinate as emulsifier. Colloids Surf A Physicochem Eng Asp 145:61–69CrossRefGoogle Scholar
  90. Schokker EP, Dalgleish DG (2000) Orthokinetic flocculation of caseinate-stabilized emulsions: influence of calcium concentration, shear rate, and protein content. J Agric Food Chem 48:198–203CrossRefGoogle Scholar
  91. Semenova MG, Belyakova LE, Polikarpov YN, Antipova AS, Dickinson E (2009) Light scattering study of sodium caseinate plus dextran sulfate in aqueous solution: relationship to emulsion stability. Food Hydrocolloids 23:629–639CrossRefGoogle Scholar
  92. Silva ACC, Arêas EPG, Silva MA, Arêas JAG (2010) Effects of extrusion on the emulsifying properties of rumen and soy protein. Food Biophys 5:94–102CrossRefGoogle Scholar
  93. Stamkulov NS, Mussabekov KB, Aidarova SB, Luckham PF (2009) Stabilisation of emulsions by using a combination of an oil soluble ionic surfactant and water soluble polyelectrolytes. I: emulsion stabilisation and Interfacial tension measurements. Colloids Surf A Physicochem Eng Asp 335:103–106CrossRefGoogle Scholar
  94. Stevenson ME, Horne DS, Leaver J (1997) Displacement of native and thiolated β-casein from oil-water interfaces—effect of heating, ageing and oil phase. J Food Hydrocolloids 11:3–6CrossRefGoogle Scholar
  95. Sun W, Sun D, Wei Y, Liu S, Zhang S (2007) Oil-in-water emulsions stabilized by hydrophobically modified hydroxyethyl cellulose: adsorption and thickening effect. J Colloid Interface Sci 311:228–236CrossRefGoogle Scholar
  96. Tangsuphoom N, Coupland JN (2008) Effect of surface-active stabilizers on the microstructure and stability of coconut milk emulsions. Food Hydrocolloids 22:1233–1242CrossRefGoogle Scholar
  97. Tangsuphoom N, Coupland JN (2009a) Effect of surface-active stabilizers on the surface properties of coconut milk emulsions. Food Hydrocolloids 23:1801–1809CrossRefGoogle Scholar
  98. Tangsuphoom N, Coupland JN (2009b) Effect of thermal treatments on the properties of coconut milk emulsions prepared with surface-active stabilizers. Food Hydrocolloids 23:1792–1800CrossRefGoogle Scholar
  99. Tipvarakarnkoon T, Einhorn-Stoll U, Senge B (2010) Effect of modified Acacia gum (SUPER GUM™) on the stabilization of coconut o/w emulsions. Food Hydrocolloids 24:595–601CrossRefGoogle Scholar
  100. Yaghmur A, Glatter O (2009) Characterization and potential applications of nanostructured aqueous dispersions. Adv Colloid Interface Sci 147–148:333–342CrossRefGoogle Scholar
  101. Yang R, Gao RC, Cai CF, Xu H, Li F, He HB, Tang X (2010) Preparation of gel-core-solid lipid nanoparticle: a novel way to improve the encapsulation of protein and peptide. Chem Pharm Bull 58:1195–1202CrossRefGoogle Scholar
  102. Yang JS, Xie YJ, He W (2011) Research progress on chemical modification of alginate: a review. Carbohydr Polym 84:33–39CrossRefGoogle Scholar
  103. Yang JS, Jiang B, He W, Xia YM (2012) Hydrophobically modified alginate for emulsion of oil-in-water. Carbohydr Polym 87:1503–1506CrossRefGoogle Scholar
  104. Zheng MY, Liu F, Wang ZW, Baoyindugurong JH (2011) Formation and characterization of self-assembling fish oil microemulsions. Colloid J 73:319–326CrossRefGoogle Scholar

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© Maria Lidia Herrera 2012

Authors and Affiliations

  • Maria Lidia Herrera
    • 1
  1. 1.Faculty of Exact and Natural SciencesUniversity of Buenos AiresBuenos AiresArgentina

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