Encapsulation Materials

Transcription

1 Encapsulation Materials Short Course on Micro- and Nano-encapsulation of Functional Ingredients in Food Products World Congress on Oils & Fats and 31 st Lectureship Series 31 st Oct 4 th November 2015, Rosario, Argentina CSIRO FOOD AND NUTRITION Mary Ann Augustin & Luz Sanguansri

2 Outline Choice of Materials Proteins as Encapsulants Gelation properties Interfacial properties Emulsifying properties Carbohydrates as Encapsulants Glassy matrices Fats as Encapsulants 2 Micro and Nanoencapsulation Technologies Augustin & Sanguansri

3 Choice of Materials 3 Materials_ Microencapsulation Augustin & Sanguansri

4 Major Types of Encapsulant Materials Only food grade / GRAS ingredients allowed Material Class Examples of types of materials Proteins Simple sugars Albumin, caseinates, gelatin, gluten, peptides, soy protein, vegetable proteins, whey proteins, zein Fructose, galactose, glucose, maltose, sucrose Carbohydrates/Gums Chitosan, corn syrup solids, cyclodextrin, dextrins, dried glucose syrup, maltodextrins, modified starches, starches Agar, alginates, carrageenan, gum acacia, gum arabic, pectins Lipids Emulsifiers Cellulose Material Edible fats and oils, fractionated fats, hardened fats, beeswax Monoglycerides, diglycerides, lecithin, liposomes, Food-grade surfactants Acetylcellulose, carboxymethyl cellulose, cellulose acetate butylate phthalate, cellulose acetate phthalate, ethyl cellulose, methyl cellulose 4 Materials_ Microencapsulation Augustin & Sanguansri

5 Choice of materials Influenced by core and microcapsule properties desired Component Core Encapsulant material Microcapsule Properties Solubility - hydrophilicity / lipophilicity/amphiphilicity Taste Stability to environmental conditions - e.g. moisture, heat, ph, salts, light, enzymes Propensity to interact with other food components Solubility, Viscosity Stability to ph, salts, temperature, shear, enzyme degradation Film forming and emulsification properties Regulatory status for food application Format for delivery (i.e. liquid or powder), Particle size Payload (bioactive core loading) Storage stability Stability to different process conditions, Release properties, Cost of production 5 Materials_ Microencapsulation Augustin & Sanguansri

6 Characteristics of encapsulant materials Each class of materials (lipids, biopolymers polysaccharides and proteins) have their own unique characteristics that influences the processes used and the applications for which they are used Fats and waxes are water insoluble and are good barriers to water and water soluble food components typically used to coat solid cores and applied using fluidised bed coating Biopolymers are water soluble and used to produce microcapsules loaded with fats, oil-soluble vitamins and solventmiscible flavours microcapsules produced usually involve spray drying or pressure extrusion 6 Materials_ Microencapsulation Augustin & Sanguansri

7 Types of nano- and microcapsules Morphologies of microcapsules: (a) single-core capsule, (b) dispersed core in polymer gel, (c) multi-layer capsule, (d) dualcore capsule and (e) single-core multi-shell capsule. Choice of encapsulant material: Requires knowledge about the inherent physical and chemical properties of the materials Influenced also by type of micro- or nano-capsule desired and trigger event for release of core Augustin & Hemar (2009), Chem Soc Rev 7 Materials_ Microencapsulation Augustin & Sanguansri

8 Encapsulant materials and their function Encapsulant materials Proteins Examples Caseins, whey proteins, soy proteins, egg proteins, pea protein, gelatin, hydrolyzed proteins Characteristics of materials useful for encapsulation Ability to build viscosity, gelling, emulsifying Sugars and glucose syrups Mono-, di- and oligo-saccharides, glucose syrups Low viscosity at high solids, ability to form glassy solids on dehydration Polysaccharides Fats and waxes Surfactants Starch, maltodextrins, gums, carboxymethylcellulose, pectins, alginates, chitosan Animal fats (e.g.milkfat), vegetable fats (e.g. canola oil), waxes (e.g. beeswax) Mono- and di-glycerides, phospholipids (e.g. lecithin), glycolipids, Tweens, Spans Gelling, emulsion stabilization, film forming, ability to form glassy solids on dehydration Solubilization of lipophilic cores, matrix for embedding cores, water barrier properties, film forming Emulsifying 8 Materials_ Microencapsulation Augustin & Sanguansri

9 Functional food microstructures for macronutrient release and delivery Norton et al. (2015) Food & Function, Materials_ Microencapsulation Augustin & Sanguansri

10 Example: Dairy ingredients used as encapsulants System Dairy encapsulant material Function of dairy ingredient Emulsions Milk proteins caseins, whey proteins, milk protein isolates, Film forming, stabilization of emulsion hydrolyzed milk proteins Milkfat, milkfat fractions Carrier of active cores Dried emulsions Milk proteins casein, whey proteins, hydrolyzed milk proteins Emulsion stabilization prior to drying, emulsion matrix of dried particle Lactose Formation of glassy matrix on drying Milkfat Carrier of active cores, secondary coating material, barrier to moisture Hydrogel Milk proteins casein, whey proteins Formation of gel phase, matrix for embedding cores Lipospheres Milkfat Entrapment of active cores Liposomes Milk phospholipids, milkfat Stabilization of bilayer vesicles globule membrane Coacervates Milk proteins casein, whey proteins Interaction with oppositely charged biopolymers to form a separate phase 10 Materials_ Microencapsulation Augustin & Sanguansri

11 Proteins as Encapsulants - Understanding properties of proteins 11 Materials_ Microencapsulation Augustin & Sanguansri

12 Food Proteins as Encapsulants Food Protein Products Animal sources (Meat, dairy, fish, egg proteins) Vegetable sources (Soy protein, wheat protein, pea, maize) Microalgal protein source (Spirulina) Protein Hydrolysates Milk Proteins - Casein/whey hydrolysates Wheat hydrolysates Soy hydrolysates Fish hydrolysates (Note: The properties of the hydroslysates will depend on the parent protein, the degree of hydrolyis and the method of hydrolysis used) Newer proteins Oleosin 12 Materials_ Microencapsulation Augustin & Sanguansri

13 Relationship b/w molecular, structure and functional properties Functional properties of proteins ( and hence encapsulation properties) are related to the physical, chemical and structural / conformational properties of proteins: Amino acid composition and sequence O Size & Shape C Conformation secondary, tertiary and quaternary Charge and their distribution Hydrophobicity/hydrophilicity ratio Rigidity / flexibility (inter and intra polypeptide linkages) N H R C H O C N H R C H O C N H R C H O C R C N H H O C N H 13 Materials_ Microencapsulation Augustin & Sanguansri

14 Structure of food proteins Collagen a fibrous protein Βeta lactoglobulin a globular protein Oleosin 14 Materials_ Microencapsulation Augustin & Sanguansri

15 Structural Properties of Milk Proteins 15 Materials_ Microencapsulation Augustin & Sanguansri

16 Structural Properties of Animal Proteins 16 Materials_ Microencapsulation Augustin & Sanguansri

17 Structural Properties of Vegetable Proteins 17 Materials_ Microencapsulation Augustin & Sanguansri

18 Physical Functionality of Protein Ingredients Solubility* Water absorption Heat Stability Viscosity Gelation* Emulsification* Foaming These functional properties of food proteins determine their suitability as ingredients in food applications (and also their functionality as an encapsulant) 18 Materials_ Microencapsulation Augustin & Sanguansri

19 Protein Denaturation Unfolding of proteins ph Heat Reducing agents Solvents (eg alcohol) High pressure Can be reversible or irreversible Irreversible egg protein denaturation on heating Materials_ Microencapsulation Augustin & Sanguansri 19

20 Protein stability and folding There is a delicate balance b/w native and unfolded state of protein Consequences of denaturation on hydration & protein functionality Altered water binding capacity Decreased solubility (due to exposure of hydrophobic groups) Loss of biological activity Increased intrinsic viscosity Others: Changes gelation and surface properties etc. 20 Materials_ Microencapsulation Augustin & Sanguansri

21 Physical functionality of proteins - Solubility Protein Solubility as a function of ph in 0.2M NaCl Solubility is lowest at the pi (isoelectric point) of the protein Solubility is a pre-requisite for many other functional properties of proteins (Cheftel et al, in Fennema, 1985) 21 Materials_ Microencapsulation Augustin & Sanguansri

22 Gelation Properties of Proteins 22 Materials_ Microencapsulation Augustin & Sanguansri

23 Gelation of protein solutions Definition Gels are formed when a viscous fluid is changed into a 3-D network with viscoelastic characteristics ( Proteins are polymerised due to favourable protein-protein interactions) Why is gelation important? Affects structure and texture of foods Eg set yoghurt, cheese, hard boiled eggs, tofu, re-formed meat product From an encapsulant matrix viewpoint gelling properties are capitalised upon in the formation of gels which entrap a core 23 Materials_ Microencapsulation Augustin & Sanguansri

24 Relationship b/w molecular and functional properties Gelation Transformation of protein from a sol to a gel-like structure Linked to ability of proteins to dissociate / denaturation Depends on molecular properties of proteins (irreversible gel or soluble aggregated formed depending on levels of various amino acids) Mechanism Network formation Water entrapment Water immobilisation Entrapment of bioactives 24 Materials_ Microencapsulation Augustin & Sanguansri

25 Factors affecting gelling properties of proteins Protein concentration For a given protein, a critical concentration is required for the formation of a gel ph Exposure to moderately high ph followed by re-adjustment to neutral ph has been shown to activate some proteins (eg yoghurt gels) Suggestions that in some proteins this is related to unfolding of protein and activation of sulphydryl groups (eg whey protein gels) ph range over which gelation occurs generally increases with protein concentration 25 Materials_ Microencapsulation Augustin & Sanguansri

26 Factors affecting gelling properties of proteins Type of salt and ionic strength Salts, through their effects on conformation of and charge of proteins, affect gelation Temperature Depends on type of protein and conditions for gelation Heating induces unfolding of proteins which leads to nonnative conformation and hence altered gelling properties (eg egg-white gels) Cooling can also cause formation of protein gels (eg gelatin) 26 Materials_ Microencapsulation Augustin & Sanguansri

27 Gelation Gel formation requires critical balance between attractive and repulsive forces Two-step process Step 1 Change in conformation (usually heat-induced) or partial denaturation of protein molecules; viscosity increases due to an increase in the molecular dimensions of unfolding proteins Step 2 Gradual association or aggregation of individual denatured proteins; exponential increase in viscosity as material approaches a continuous network (NOTE: If Step 2 is too fast compared to Step 1, a random network that is not able to hold water is formed and syneresis occurs) Materials_ Microencapsulation Augustin & Sanguansri

28 Capitalising on the gelling properties of proteins 28 Materials_ Microencapsulation Augustin & Sanguansri

29 Food protein-based delivery systems for delivery of bioactives Chen et al. (2006) Trends in Food Science & Technology 17, Materials_ Microencapsulation Augustin & Sanguansri

30 Changes in protein structure with ph ph far from pi ph near pi ph far from pi Fibrous gels ph near ph Particulate gels Different encapsulating and release properties of same protein at different ph 30 Materials_ Microencapsulation Augustin & Sanguansri

31 ph-sensitive Iron delivery from particulate and fine stranded beta-lactoglobulin gels ph 1.2 (Gastric ph) ph 7.5 (Intestinal ph) Release from filamentous (solid line) and particulate (dashed line) gels Under acidic conditions iron release from filamentous gels is lower than from particulate gels At ph 7.5 initial relatively rapid release phase (first 30 min) followed by a slower sustained release in the case of filamentous gels Remondetto et al. (2004) J. Agric. Food Chem. 52, Materials_ Microencapsulation Augustin & Sanguansri

32 Cold-set whey protein microgels for the stable immobilization of lipids Micron-sized (below 100 mu m in diameter) internally gelled matrices > 95% retention of lipids Migration of exterior oil, during the O/W/O production process, into the microgels was also avoided. SEM revealed voids uniformly distributed throughout the matrix Feasibility for the stable inclusion of a wide range of sensitive lipophilic bioactive ingredients into these matrices, where the sub-millimeter size of the microgels represents potential for incorporation into a variety of food systems. Egan et al. (2013). Food Hydrocolloids, 31, Materials_ Microencapsulation Augustin & Sanguansri

33 Interfacial Properties of Proteins 33 Materials_ Microencapsulation Augustin & Sanguansri

34 Proteins at Interfaces Interfacial properties are exploited Film forming Foam formation and stabilisation Emulsion formation and stabilisation Behaviour of proteins are different from small M.W. surfactants although both can reduce surface tension Proteins are large molecules with amphiphilic properties adsorption occurs at an interface with multiple points of contact Large portions of the protein remain in the aqueous phase Mechanism : Diffusion, adsorption, unfolding & re-arrangement Flexible proteins such as ß-casein readily unfold and reduce surface tension (cf rigid proteins that are resistant to unfolding) Bonds involved in formation and stabilisation of an interface are similar to those involved in gelation 34 Materials_ Microencapsulation Augustin & Sanguansri

35 Relationship b/w molecular and surface properties Surface properties of proteins are dependent on their ability to lower interfacial tension Surface-active properties of proteins (ie film forming, emulsifying) Related to the content of hydrophobic and hydrophilic amino acids and their distribution (ie degree of amphiphilicity) Depends on their ability to move to interfaces, adsorption at interface, film formation 35 Materials_ Microencapsulation Augustin & Sanguansri

36 Factors affecting interfacial properties of proteins Intrinsic Amino acid composition Ratio of polar:non-polar amino acids Distribution of hydrophobic and hydrophilic groups Secondary, tertiary and quaternary structure of proteins Disulphide bonds and free thiol groups Extrinsic ph Ionic strength and species Protein concentration Time Temperature Molecular shape and size Energy input Molecular flexibility Protein Structure-Function Relationships in Foods, Ed. R.Y. Yada, R.L. Jackman and J.L. Smith, 1994, pg 112 Materials_ Microencapsulation Augustin & Sanguansri

37 Structural Forces affecting Protein Films at Interfaces Interaction Hydrophobic Hydrogen Ionic Cation bridges Covalent Electrostatic repulsion Effect Initiates contact with interface, Strengthens films Increases association of protein chains Increases cross-links between oppositely charged groups Cross-links involving metal ions (eg Ca) Bridging; Ordering Repulsion between like charged groups Materials_ Microencapsulation Augustin & Sanguansri

38 Factors affecting emulsion stability Surface hydrophobicity and molecular flexibility Electrostatic forces Repulsive forces prevent coagulation of droplets Steric effects ph Temperature Protein Structure-Function Relationships in Foods, Ed. R.Y. Yada, R.L. Jackman and J.L. Smith, 1994, pg 159 Materials_ Microencapsulation Augustin & Sanguansri

39 Capitalising on the emulsifying properties of proteins Protein-stabilised emulsions 39 Materials_ Microencapsulation Augustin & Sanguansri

40 Oil-in-water emulsions (General Concept) Emulsifiers (surfactants) stabilize a colloid by lowering surface tension. Food emulsifier: low molecular weight surfactant (e.g. Tween, phospholipid) - high molecular weight surfactant (e.g. proteins, some polysaccharides gum arabic, sugar beet pectin) WATER Continuous Phase OIL Dispersed phase EMULSIFIER Interfacial Region Emulsion-based systems are suitable for delivery of lipophilic food ingredients (e.g. omega-3 oils, carotenes, tocopherols). 40 Materials_ Microencapsulation Augustin & Sanguansri McClements, Decker & Weiss (2007) Food Sci., 72, R109

41 Emulsifying properties of some food proteins Protein Surface hydrophobicity Emulsifying capacity Ovalbumin S Globulin κ-casein ß-lactoglobulin Serum albumin Emulsifying stability Protein Structure-Function Relationships in Foods, Ed. R.Y. Yada, R.L. Jackman and J.L. Smith, 1994, pg 161 Materials_ Microencapsulation Augustin & Sanguansri

42 Protein-stabilised emulsions Protein conformation at O/W interface Flexible caseins adsorbed as loop-train and tail-train configurations via hydrophobic residues (shown in red) Globular proteins adsorbed via exposing hydrophobic α- helices (shown in red) by conformation changes at the O/W. Oleosins adsorbed both at hydrophobic regions in amphipathic regions as well as a central hydrophobic pin (shown in red Rayner (2015), Curr Opin Food Sci, 3, (2015) 42 Materials_ Microencapsulation Augustin & Sanguansri

43 Destablisation of protein-based emulsions CryoSEM image of microgel stabilized emulsion droplets showing two levels of microgel compaction and packing, (scale bar is 2 μm) Higher shear: Bridged emulsions and flocculation Dispersed emulsions creamed and remain freeflowing Rayner (2015), Curr Opin Food Sci, 3, (2015) 43 Materials_ Microencapsulation Augustin & Sanguansri

44 Carbohydrates as Encapsulants - Understanding properties of carbohydrates 44 Materials_ Microencapsulation Augustin & Sanguansri

45 Carbohydrates in Foods Content in common foods Sugar: Coke 9%, ice cream 18%, dry cake mix 36% Starch (amylose-amylopectin): Wheat 59%, rice 70% Major reactions Sugars: Hydrolysis, thermal degradation, Maillard reaction (non-enzymic browning reaction between reducing carbohydrates and proteins) Starch retrogradation (staling of bread) Functional properties Mono oligosaccharides: humectancy, flavour Starch / polysaccharides pectins, alginates, cellulose: gelling, viscosity Materials_ Microencapsulation Augustin & Sanguansri

46 Gelation of alginates Alginate made of β-d-mannuronic and α-l-guluronic acids joined by 1-4 linkages Gels in the presence of calcium Schematic of a calcium alginate gel Materials_ Microencapsulation Augustin & Sanguansri

47 Encapsulation by extrusion and gelation air driven simple needle droplet-generator spinning disk device Materials_ Microencapsulation Augustin & Sanguansri Burgain et al 2011, Food Eng

48 Droplet Generator Production of alginate beads containing thyme extract Total phenol and rosmarinic acid loadings in the hydrogel delivery system correspond to the contents in the original thyme aqueous extract. Thyme polyphenolic compounds appeared to be chemically stable and antioxidant activity was preserved upon immobilisation. Stojanovic et al. (2012) J Sci Food Agric, 92, Materials_ Microencapsulation Augustin & Sanguansri

49 Carbohydrate Glassy Matrices 49 Materials_ Microencapsulation Augustin & Sanguansri

50 Glass Transition 50 Materials_ Microencapsulation Augustin & Sanguansri

51 Glassy matrices Glass transition temperature (Tg) Property of a material Tg decreases when water activity is increased Glassy state Temperature below Tg - Mobility of molecules is extremely slow - Reactions are arrested - Sensitive cores are protected [E.g. flavours in a boiled sweet (sugar glass) is entrapped until release in the mouth when the sweet is wetted] 51 Materials_ Microencapsulation Augustin & Sanguansri

52 Carbohydrate Glasses Protect oxygen sensitive cores Oxidation of oxygen sensitive cores (eg unsaturated oils) depends on the physical state of the encapsulating matrix the availability of oxygen and its access to the matrix Since the glass transition modifies the matrix structure, it is expected that the stability of the encapsulated compound will be affected above the glass transition temperature (T g ). 52 Materials_ Microencapsulation Augustin & Sanguansri

53 Degradation of β carotene in amorphous polymer matrices. Effect of water sorption properties and physical state Maltodextrin/gelatin Maltodextrin/gum arabic Maltodextrin β-carotene losses were observed mainly at relative humidities (RHs) above the glass transition temperatures ( Tg) where the matrices were fully plasticised and collapsed (75 and 92% RH). Pigment degradation was determined by the physical state of the matrix, and related to the degree of collapse. Ramoneda et al. (2011) J Sci Food & Agric, 91, Materials_ Microencapsulation Augustin & Sanguansri

54 Flavour retention in glass carbohydrate matrices Flavour microcapsules containing amorphous carbohydrate as wall material can undergo changes during handling and storage - crystallisation - clumping - sticking - caking Such physical changes may lead to the release of entrapped flavours Retention of flavour is governed by - Wall material: physical changes (which may result in release of core) - Core: chemical nature of core, its molecular weight, polarity 54 Materials_ Microencapsulation Augustin & Sanguansri

55 Spray drying encapsulation of citral in sucrose or trehalose matrices: physicochemical and sensory characteristics Citral retention after spray-drying was similar for both trehalose and sucrose matrices Physical stability of trehalose formulations was better as compared to sucrose Sosa et al, (2011) Int J Food Sci & Tech, 46, Materials_ Microencapsulation Augustin & Sanguansri

56 Effect of caking and stickiness on the retention of spray dried encapsulated orange peel oil Advanced caking Surface caking Retention at 35C Glass transition The volatiles are protected and retained by mesquite gum as long as the capsule structure remains intact Beristain et al. (2003) J Sci Food & Agric, 83, Materials_ Microencapsulation Augustin & Sanguansri

57 Fats as Encapsulants - Understanding the functional properties of fats 57 Materials_ Microencapsulation Augustin & Sanguansri

58 Fat Ingredients Traditional Fat Products Animal fats eg milkfat, tallow, lard Vegetable fats eg palm, canola, olive Modified Fats fractionation, interesterification, hydrogenation Factors affecting fat functionality Flavour Chemical Composition Fatty acids, triglycerides, minor lipids Melting and Crystallisation Behaviour Polymorphism Solid-to-liquid fat ratio Microstructure Processing Conditions 58 Materials_ Microencapsulation Augustin & Sanguansri

59 Liquid Nanoemulsion and Solid Lipid Nanoparticles 59 Materials_ Microencapsulation Augustin & Sanguansri

60 Nano-emulsions 60 Materials_ Microencapsulation Augustin & Sanguansri

61 Solid Lipid Nanoparticles Compared to nanoemulsions and liposomes, SLN s have the following advantages High encapsulation efficiency Provide high flexibility in controlling the release profile due to solid matrix Slower degradation rate allows bioactive release for prolonged times. The solid matrix can (but need not) protect the incorporated bioactive ingredients against chemical degradation 61 Materials_ Microencapsulation Augustin & Sanguansri

62 Further Reading Augustin, M.A. and Hemar, Y., Nano-structured assemblies for encapsulation of food ingredients. Chemical Society Reviews, 38, pp Garti, N. ed., Delivery and controlled release of bioactives in foods and nutraceuticals, Woodhead Publishing Limited, Cambridge, England. Gouin, S., Microencapsulation: industrial appraisal of existing technologies and trends. Trends in Food Science and Technology, 15 (7-8), pp dekruif, G.G., Weinbreck, C.G. and de Vries, R Complex coacervation of proteins and anionic polysaccharides. Current Opinion in Colloid & Interface Science, 9, pp Madene, A., Jacquot, M., Scher, J. and Desobry, S., Flavour encapsulation and controlled release a review. International Journal of Food Science and Technology, 41 (s1), pp McClements, D.J., Decker, E.A., Park, Y. and Weiss, J., Structural design principles for delivery of bioactive components in nutraceuticals and functional foods. Critical Reviews in Food Science and Nutrition, 49, pp Materials_ Microencapsulation Augustin & Sanguansri

63 Thank you CSIRO Food & Nutrition Mary Ann Augustin Research Group Leader t e maryann.augustin@csiro.au