Lipids I PDF Lecture Notes

LIPIDS I Prof. Jetty C.Y. Lee School of Biological Sciences Email: [email protected]  Learning Outcomes Students will learn the types of lipids found in food Students will learn the structure and state of the lipids found in food Students will learn phys...

LIPIDS I Prof. Jetty C.Y. Lee School of Biological Sciences Email: [email protected]  Learning Outcomes Students will learn the types of lipids found in food Students will learn the structure and state of the lipids found in food Students will learn physical properties of lipids The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 2  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Lipids 3  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Oil or Fat? Lipids Oils (liquid) Fat (solid) Sunflower Animal Soybean Butter Sesame Ghee Peanut Lard Corn Tallow Rice Canola Olive Cotton Vegetable 4  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Fat content in foods 5  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Lipids Three primary groups: Triglycerides (Triacylglycerols: fatty acids esterified to glycerol; 99% of fatty acids in plants and animals): important component of cell membrane Phospholipids (modified triacylglycerols, e.g. lecithin emulsifier) Sterols (non-polar e.g. cholesterol precursor of bile acids and vitamin D) Waxes (includes wax esters, sterol esters, ketones, aldehydes, alcohol and sterol e.g. beeswax): food wraps (repels water), also used for fruit coating to slow transpiration moisture loss during storage 6 Triglyceride abbreviations in Food Chemistry Triglycerides can be abbreviated by using the first letters of the common names of the component fatty acids StStSt: tri-stearin (stearic acid) PPP: tri-palmitin (palmitic acid) StOSt a triglyceride with two stearic acid residues in the 1 and 3 positions and oleic acid in the 2 position Glyceride compositions are expressed in terms of saturated (S) and unsaturated (U) component fatty acids S and U are used, and glycerides would be indicated as SSS for tri-saturated glyceride and SUS for a glyceride with an unsaturated fatty acid in the 2 position The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 7  Formation of triglyceride from glycerol and fatty acids oil unsat liquid plant : -> Animal fat : sat > - solid ! The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 8  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Fatty acids Majority of lipids are derivatives of fatty acids (FA) Fatty acids with a carboxyl (-COOH) group at one end (polar) and a methyl group (- CH3) at the other end (non-polar) Nomenclature: Saturated Fatty Acid (SFA) Monounsaturated Fatty Acid (MUFA) Polyunsaturated Fatty Acid (PUFA) Fatty Acids Saturated Polyunsaturated Monounsaturated (C18) Acetic acid (C4, Short) (C18-C22) Olive Oil Coconut Oil (C8, Medium) Sunflower oil, Corn oil, Fish oil Animal (C>8, Long) We distinguish them by carbon numbers and carbon-carbon double bonds 9  Structure of fatty acid A fatty acid consists of a methyl group and a carboxyl group Methyl group unreactive react with ound com other 10 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee.  4 ↑ C C ↑ Bent ↓M =. Nomenclature of fatty acid Degree of saturation, examples: Saturated: - Palmitic (C16:0) - Stearic (C18:0) Monounsaturated - Oleic (C18:1) Polyunsaturated - Linoleic acid (C18:2) →2 double bonds - Linolenic acid (C18:3) → 3 double bonds 11 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Classification and structure: Saturated fatty acids Common Name Systematic Name Formula_____ ' Butyric acid n-butanoic (C4:0) !"#$!"%C%! '" ( Caproic acid n-hexanoic (C6:0) !"#$!"%C'! (" ( Caprylic acid n-octanoic (C8:0) !"#$!"%C'! (" ( Capric acid n-decanoic (C10:0) !"#$!"%C'! (" ) Lauric acid n-dodecanoic (C12:0) !"#$!"%C'(! )" 12 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Saturated fatty acids Straight chain molecules Form a crystalline structure, resulting in a solid fat at room temperature The appearance (rough, smooth, shiny), hardness, and light reflection characteristics (colour) The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 13 Nomenclature of unsaturated fatty acids Location of double bonds A method of nomenclature that designates the number of carbons between the terminal –CH3 group and the last double bond in the fatty acid (FA) - Omega-3 (ω3) FAs - Omega-6 (ω6) FAs Omega 3 Fatty Acid H HH H 3 2 1 Large carbon R-C-C=C-C-C-H Methyl end chain Double HH bond The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 14  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Polyunsaturated fatty acids Linoleic acid: Cis, cis, 9, 12-Octadecadienoic acid Linolenic acid: Cis, cis, cis 9,12,15-Octadecatrienoic acid Arachidonic acid: Cis, cis, cis, cis 5,8,11,14-Eicosatetraenoic acid naturally found cis form : ↓ Bent In mammals Arachidonic acid Linoleic acid g -Linolenic acid Arachidonic acid 15 Omega-3 and Omega-6 fatty acids 16 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee.  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Essential fatty acids Omega 6 sources > - induce inflammatory Linoleic acid Vegetable oils (corn, sunflower, safflower, soybean, = cottonseed), nuts, seeds Arachidonic acid Meats, poultry, eggs or can be made from linoleic acid Omega 3 sources anti-inflammatory > - Alpha-Linolenic acid Oils (flaxseed, canola, walnut, wheat germ, soybean), I nuts and seeds (butternuts, flaxseeds, walnuts, soybean kernels), vegetables (soybeans) EPA and DHA Human milk fatty fish not white fish , Pacific oysters and fish (mackerel, salmon, bluefish, mullet, anchovy, sardines, tuna, herring) or can be made from linolenic acid Yield a slow in our very body 17 low efficiency. Cis and trans configuration of fatty acids For unsaturated fatty acids only cis configuration - The carbon chains on the 2 sides of the double bond bent towards each other - The hydrogen atoms on the double bond are on the same Kink side 18 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Cis and trans configuration of fatty acids For unsaturated fatty acids only Trans configuration - The hydrogen atoms on the double bond are opposite to each other - As a result, the chain is nearly straight ↳ solid 19 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Fat composition of foods Pork fat Depot fats of higher animals - Mainly palmitic, oleic and stearic acids - About 70% saturated fatty acids Ruminant milk lipids e.g. cattle, goat, sheep - Major fatty acids are palmitic, oleic and stearic Palm acids - Some are short chain saturated fatty acids (C4- C10) Maybe good for human. short chain sat the only good > - Fruit coat fats are from our got - Mainly palmitic, oleic and some linoleic acids Coconut The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 20  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Fat composition of foods Marine and algal oils the white live in salmon. - Low in saturated FAs > - - High in unsaturated FAs - Examples (health interest): Eicosapentaenoic acid (EPA, 20:5ω3) Docosahexaenoic acid (DHA, 22:6ω3) EPA/DHA Algal oil > - low O efficiency minimum a Perdana et al. https://doi.org/10.1016/j.algal.2021.102542 21 ALA is good for heart but EPA and DHA are better > - ALA can convert to EPA and DHA but low efficiency Fat composition of foods Seed fats (corn, olive oils) - Low in saturated FAs - Contain mostly palmitic, oleic, linoleic and linolenic acids Olive Coconut and palm oils - Contain mainly short chain fatty acids (SCFAs) and medium chain fatty acids (MCFAs), rich in lauric acid - Coco butter contains mainly palmitic, stearic, oleic acids The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 22  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Physical properties of lipids Physical properties of fat depend on - Chemical composition: lipids in food varies slightly with climate, soil and with nutrition, season and breed for animal oils (v ). heat solid - Melting point and solidification of fats butter are extracted oil > - > -... - Crystalline structure - The orientation of same surface-active compounds to promote formation of emulsions 23 Physical properties of lipids: Melting points (m.p.) Melting point - Basically, determined by the m.p. of Fatty Acid M.P. (°C) constituent FAs: not the best identification C18:0 Stearic 69 method as fat melts over a range of C20:0 Arachidic 75 temperatures C18:1 Oleic 13.4 - Factors affecting m.p. C18:2 Linoleic -5 Chain length (longer chain, high m.p.) C18:2 (trans) Linolelaidic 28 stabilized Unsaturation (saturated ones, higher m.p.) C18:3 Linolenic -11 Configuration (trans fatty acids, higher m.p.) C20:4 Arachidonic -50 General rule: m.p. of ↑ C C= ↓ M P. saturated FAs > trans FAs > cis FAs 24 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Physical properties of lipids: Solubility Long-chain fatty acids are practically insoluble in water The polar carboxyl groups in this film are oriented toward the water, while the hydrophobic tails protrude into the gaseous phase The solubility of the acids increases with decreasing carbon number; butyric acid (C4) is completely soluble in water H002 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 25  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Physical properties of lipids Solid State: - Lipids can exist in many forms of solid state - The solid character of fats is the result of the presence of a certain amount of crystallized fats Crystal lattice Crystal size (0.1 μm to 100 μm) - Fats with large crystals become grainy to see and taste (not smooth) - The crystals are held by Van der Waals force (intermolecular forces) - Amount and size of crystals determine the physical properties of the fat - Slow cooling causes formation of layer of crystals on top of one another e.g. chocolate, biscuits etc and biscuit 26 * V chocolate.: heat the cake Cake melt > - (cook  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Crystallization of fats Solid-liquid phase transitions are an integral part of many processing and required to produce food products e.g margarine, butter, ice-cream, whipped cream Crystallization of fats determines important properties of foods, including: - It affects the consistency and plasticity of butter, margarine and chocolate during the stages of production and storage e.g. sensory properties such as the melting sensation in the mouth (e.g. chocolate) determine the hardness - Physical stability with respect to the formation and settling of crystals, oil exudation (in processing for cooking oil) and coalescence of particles and emulsions (e.g. butter and mayonnaise) extract- heat > crystal form - tgt (Emulsion butter > more > a - - - Visual appearance, for example the shininess of chocolates and toppings. In most foods, crystallization of TAGs is considered greatest importance, although the crystallization of minority lipids such as DAGs, MAGs and phospholipids plays a fundamental role in the quality of various products emulsities phospholipid > - 27  fatmigrateout -vogformcyta The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. structure. Mechanism of crystallization &Fat Bloom: loss of gloss, ↓ The process of crystallization includes the nucleation and grey-whitish haze on surface crystal growth Nucleation: formation of aggregates of molecules that have exceeded a critical size and are therefore stable A nucleus is the smallest crystal that can exist in a solution in a certain temperature Slow Fast Once a crystal nucleus has formed, it begins to grow and pack by incorporating other molecules from the adjacent liquid bigger crystal join by Van der Waal forces layer, which is continuously filled by the supersaturated liquid that is around the crystal There is a continuous movement of molecules on the surface of the crystal, and the result of these processes determines the growth rate, which is directly proportional to the subcooling and varies inversely with the viscosity system stop the formation of crystal by cooling 28  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Physical properties of lipids: Polymorphism (stability) a Polymorphism: Existence of several different crystal forms for a same of solid or semsoid compound after heating and supercooled; ability to manifest different unit cell structures because of various molecular packings Formed from long-chain compounds, such as fatty acids and their esters (TAG); solids with the same composition that can exist in more than one crystalline form are called polymorphs Note: In a fat, crystals are solids with atoms arranged in a regular 3D pattern. A cell is the repeating unit that makes up the integral structure of a given crystal. A sub-cell, is the smallest periodic structure that exists in the actual cell unit, being defined as the transverse mode of packing of the aliphatic chains in TAGs unstable Sub-cell occur in 3 different polymorphic forms: alpha (!), beta prime ("’) and beta ("): from less stable to more stable form Stable 29 Polymorphism " form: the most stable and highest melting point Melting point: " > "’ > ! e.g. tristearin 73.3°C > 64.0°C > 54.7°C each form has characteristic melting points solid form. "’ form: intermediate in stability and melting point ! form: the least stable and lowest melting point - Polymorphic transition from less stable to more stable form is irreversible and takes place ! ® "’ ® " The polymorphic forms are distinguished by differences in the angle of tilt of the unit cell in the crystal The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 30  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Polymorphism ! hexagonal "’ orthorhombic " triclinic - Chains are randomly oriented - Alternate chain planes are - All zig-zag planes are parallel - Crystals are fragile, 5 μm in perpendicular to their adjacent - Crystals are large, 50 μm in size size planes - Crystals are tiny needles not more than 1 μm long Nucleus Nucleus L Nucleus Go difficult to structure a stable crystal 31  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. What determines polymorphism type? Purity of the fat: the specific composition of a fat is one of the most important factors for the final development of the crystalline structure e.g. Palm oil is obtained from the mesocarp of the fruit Elaesis guineensis. It is semi-solid at room temperature, consisting mainly of TAGs of palmitic and oleic acids. Palm oil is the world’s largest vegetable oil used in the food industry that provides !’ crystal structure > semi-solid - Temperature (chocolate) determine type of mystal form Rate of cooling OVP8XP Presence of crystalline nuclei (centre of the crystal): A nucleus is the smallest crystal that can exist in a solution at a certain temperature. Phospholipids crystallize at higher temperatures compared to TAGs; they can act as crystallization nuclei too Bigger - Emulsifiers: foods high in fat, emulsifiers can be used to control or modify the crystallization properties of the fat phase 32  Polymorphism Polymorphic behavior in commercial fats Polymorphic behavior in commercial Fats that tend to crystallize in the !’ form fats (more stable) Fats that tend to crystallize in the ! form - Soybean - Cottonseed - Safflower - Palm - Sesame - Milk fat (ghee) - Peanut - Tallow - Corn - Olive - Coconut - Palm kernel - Lard - Cocoa butter 33 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Formation of TAG polymorphs Alpha (" ) Beta Prime (! ’) Beta (! ) Rapid cooling of liquid fat Slow cooling of liquid fat Very slow cooling of liquid fat Polymorphic transformation Polymorphic transformation of the " form of !’ Polymorphic behavior in commercial fats influenced by: - Composition of its fatty acids (saturated vs unsaturated) - Positional distribution of fatty acids in the TAG 34 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Temperature and different crystal formation TAG) Tristearin 13 steric acids on Heat Melt Drop into dry ice pieces Heat Cool Melts at 55°C and Resolidification " Solid Heat Melts at 64°C and Resolidification !’ Heat Melts at 73°C and Resolidification ! The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 35  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. & Remember: Change of cocoa butter (CB) crystal ! ® "’ lattice in Cooling process X ! ← "’ (Rapid) (slow) (slow) 36 X ↑x + B X + ↑B  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Crystallization of fats: Industrial relevance of cocoa butter Cocoa butter is an important component used in the manufacture of chocolates; 97 % of TAGs, mainly the saturated-unsaturated-saturated type (SUS) Polymorphism of cocoa butter is directly linked to the quality of the product and the processing performance Cocoa butter must be precrystallized or tempered before the molding or coating step in and chocolate production -depends melting on cooling temp Tempering induce the formation of nuclei of type βV crystals, which give the desirable characteristics to the product The formation of fat bloom in chocolate adversely affects the appearance and texture attributes Fat bloom is a function of the migration of the cocoa butter to the surface, which is deposited in the form of crystals with dimensions between 4 and 5 μm ( - hustable fat move to the surface) 37 Polymorphism of cocoa butter in chocolate and temperature In the production of chocolate, cocoa butter must be pre- crystallized or tempered before the molding or coating steps. Tempering, characterized by certain protocols ‘time x temperature’, is employed to promote = the crystallization of the more stable polymorph. In chocolate, tempering should induce the formation of nuclei * of type βV crystals, which give the # desirable characteristics to the product 38 39 Crystallization of fats: Industrial relevance of shortening Mainly palm oil contain alot of B A semisolid fat used in food preparation Promotes a "short" or crumbly texture Applied to any fat that is used for baking, and which is solid at room temperature; some ingredients refer to as hydrogenated vegetable oil which is solid at room temperature Health concerns - Vegetable shortening is damaging to human-when contains trans fats in the form of partially hydrogenated vegetable oil i.e. crisco (1g/12g fat). 40 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Shortening 41  Shortening and incorporation of air in food processing !’ crystals can trap large amount of small air bubbles !’ crystals in shortening: good for bake goods. - Small: even distribution> - - Whiter, creamier, more tender, smoother texture to use in food processing - Uniform and glossy texture in food products X 100 % B' ↳ Shortening also contain ! crystals Just small amount of ! small is capable of trapping large air bubbles ! crystals in shortening: - Large clustered crystals - A waxy or grainy texture in food products The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. 42  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Emulsions and emulsifiers Emulsifiers are functional additives of utmost importance in the food industry Amphiphilic molecules, usually with long hydrocarbon chains, characterized by simultaneous & hydrophilic and lipophilic properties Food high in fat, emulsifiers can be used to control or modify the crystallization properties of the fat phase Emulsifiers with different hydrophobic properties can affect the dynamics of crystallization of fats and oils, accelerating or slowing down this process, as well as the polymorphic transitions Emulsifiers can act as inhibitors of fat bloom, adsorb at the interface, lower fat unable to hydrophilic interfacial tension between the two more up totheeare = - hydrophobic immiscible liquid phases, provide physical resistance to coalescence in food, improve the smoothness (texture) 43 give the food. trap fat inside the food.  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Emulsions and emulsifiers Examples - Sorbitan esters are recognized for their ability to modify the crystalline morphology and consistency of fats, with effectiveness as anti-bloom agents in confectionery products containing cocoa butter and cocoa butter substitutes. Stabilizes the polymorph β′ in margarine - Fatty acids derivatives e.g polyglycerol esters. Used in desserts like e cakes and their icings> butter icing contain lot oftran > - - it stabilize Sorbitan monoester - Mono- and diglycerides: water molecules that need to be dispersed in a fat phase; monoglycerides serve as an instrument that fairly distributes water into the oil. Monoglycerides also stablises " crystals in food products 44 Emulsions and emulsifiers Emulsion: heterogenous system consisting of 2 immiscible phases; one non-dispersed, continuous phase immediately dispersed in another discontinuous phase as droplets or liquid crystals with a diameter generally 0.1mm Two types: - Oil in water (o/w) emulsion - Water in oil (w/o) emulsion Not stable Immiscible oil in water 45 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee.  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Emulsions and emulsifiers Oil in Water Emulsions (o/w) Water in Oil emulsions (w/o) Colloidal dispersion in which Colloidal dispersion in which droplets droplets of oil are dispersed in water of water are dispersed in oil e.g. butter e.g. milk, cream, mayonnaise, salad and margarine dressings, ice cream mix and cake batters adding emulsifier to stabilize Sorbitan esters can Mono- and diglycerides be used to stabilize can be used to stabilize Water droplets dispersed phase Interface 46 Emulsions and emulsifiers Meat Emulsions - Fat (solid) dispersed in the continuous phase of an aqueous matrix - Contains of salts, soluble and insoluble proteins, connective tissue etc * 47 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee.  Natural emulsifiers Phospholipids are natural emulsifiers - Found in soybean and egg yolk - Lecithin: A robust and efficient emulsifier, lecithin is a phospholipid found in egg yolks and soy that encourages oil in water (o/w) emulsions. The lecithin in one egg yolk can emulsify about 7 ounces (200 ml) of oil, and you will visibly see the emulsion spread and thin out - 10% phospholipids from egg yolk can be used to stabilize the emulsions in mayonnaise, salad dressing and cake add egg in cake - The use of lecithin enables the reduction of fat levels in many chocolate formulations. Lecithin reduce viscosity, improve snap and resistance to fat bloom and temperature variations in chocolate (v ). 48 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee.  (v ). Natural Emulsifiers In general, emulsifying agents should be first added and mixed with the continuous phase (like vinegar), so it can effectively coat the dispersed phase (like oil) as it’s being whisked to effectively create a stable emulsion Cholesterol: The cholesterol in eggs also encourages oil in water emulsions Mustard: Contains a complex polysaccharide component to aid in emulsification, but not as useful over long periods of time compared to lecithin Mayonnaise: Due to the mixture already being a stable emulsion which contains lecithin, a small amount can be added to promote a uniform suspension (in food products) Honey: Honey helps to break apart fats that accumulate together, however not as effectively as lecithin 49 The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee.  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Emulsions and emulsifiers Polar heads Preparation of an emulsion - Physical spreading needed by beating, stirring or shaking - Emulsifying agent needed: To split the two phases into droplets Semi-Permanent: Hollandaise Sauce Contains 2 distinct sections: hydrophilic (polar) and butter plus egg yolk (light whisk in warm condition) hydrophobic (non-polar) Types of emulsion: Permanent emulsion e.g. Mayonnaise Semi-Permanent emulsion e.g. Hollandaise sauce Permanent: Mayonnaise oil plus egg yolk (whisk or Emulsion: Both have good stability because of the viscous beating) nature of the liquid constituting the continuous phase 50  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Emulsions Temporary emulsion - Emulsion that has very little emulsifying agent. Before After Need to shake the ingredients for mixing - Produces Temporary Emulsion - Immediately before use, e.g. oil mixed vinegar dressing - Add Seasonings (herbs/species, e.g. ground pepper). The finer the particle size of these seasonings powder, the more effective is their action as emulsifiers 51  The University of Hong Kong, Copyrighted and All Rights Reserved, Dr. Jetty Lee. Emulsion: Stability lecithin Factors affect the stability of emulsions - The viscosity of the continuous phase - The presence and concentration of an emulsifying agent - The size of the droplets - The ratio of the dispersed phase to the continuous phase - Heating increase fluidity and encourages the emulsion to break (Hollandaise) - Freezing breaks emulsions because the water Lecithin inserts itself between the fat globules, which helps expands as ice crystals form (lecithin used to the fat globules to clump together and, as a result, the air bubbles that are present in the mix are trapped by this stabilize ice cream) partially coalesced fat. This adds firmness and texture to the ice cream, enabling it to retain its shape. 52