Emulsions: Oil and Water Mixing

• Brain teaser activity involves creating 5 groups.
• Each group should have between 3 to 6 members.
• A group member should represent their group in front of the class.
• Each group picks a task to perform.
• After 3 minutes of team collaboration and discussion, the representative executes task.
• Afterward, the leader explains the output/execution of their group.
• Possible tasks include working with oil and water, and/or an emulsifier.
• Question: Can oil and water be mixed? If no, why not? If yes, how?
• The project requires creating a 3D model of particles of water/oil, oil/water, waer/oil/water, oil/water/oil, and/or oil/emulsifier/water.

Emulsions

• The word "emulsion" comes from the Latin word for "to milk".
• Emulsions consist of a mixture of two or more liquids.
• The liquids in an emulsion are normally immiscible, i.e non-mixable or unblendable.
• Emulsions are part of a more general class of two-phase systems of matter known as colloids.
• Emulsions should be used when both the dispersed and continuous phases are liquids.
• Emulsion examples include vinaigrettes, milk, and mayonnaise.
• Cutting fluids for metal working and the photo-sensitive side of photographic film are also examples of colloids.

Types of Emulsions

• Four types of emulsions exist:
• Oil in water (O/W)
• Water in oil (W/O)
• Multiple emulsions (O/W/O or W/O/W)
• Microemulsions

O/W and W/O Emulsions

• In O/W emulsions, water is the dispersion medium and oil is the dispersed phase.
• O/W emulsions are non-greasy and easily removable from the skin.
• O/W emulsions are used externally to provide a cooling effect, like vanishing cream.
• Bitter tastes of oils can be masked in O/W emulsions, so they are preferred for internal use.
• In W/O emulsions, oil is the dispersion medium and water is the dispersed phase.
• W/O emulsions are greasy and not water washable.
• W/O emulsions are used externally to prevent evaporation of moisture from the skin, like cold cream.
• W/O emulsions are preferred for external use.

Multiple Emulsions

• Multiple emulsions consist of an emulsion system in which the dispersed phase contains smaller droplets.
• These droplets have the same composition as the external phase.
• Two types of multiple emulsions:
• Oil-in-water-in-oil (O/W/O)
• Water-in-oil-in-water (W/O/W)
• In O/W/O systems, an aqueous (hydrophilic) phase separates internal and external oil phases.
• O/W/O involves water droplets surrounded in an oil phase, which encloses one or more oil droplets.
• In W/O/W systems, an organic (hydrophobic) phase separates internal and external aqueous phases.
• W/O/W involves oil droplets surrounded by an aqueous phase, which encloses one or several water droplets.
• W/O/W systems are the most studied among multiple emulsions.

Microemulsions

• Microemulsions are clear, stable, liquid mixtures of oil, water and a surfactant, and frequently a co-surfactant.
• Microemulsions form upon simple mixing of components and don't require high shear conditions.
• Ordinary emulsions usually require high shear conditions.
• Two basic types of microemulsions exist:
• O/W
• W/O
• Microemulsions differ from macro emulsions in that they appear as a clear transparent solution.
• Internal phase droplet diameter ranges between 10-200nm.
• Microemulsions are thermodynamically stable.

Detection Tests

• A dilution test is based on the solubility of external phase of emulsion.
• An O/W emulsion can be diluted with water.
• A W/O emulsion can be diluted with oil.
• A conductivity test notes that water is a good conductor of electricity while oil is a non-conductor.
• Water runs electricity more than oil.
• A dye-solubility test notes that when an emulsion is mixed with a water-soluble dye (e.g., amaranth) and observed under a microscope:
• If the continuous phase appears red, it is an O/W emulsion.
• If the scattered globules appear red and the continuous phase colorless, it is a W/O emulsion.

Emulsifying Agents

• Emulsifying agents are soluble in both water and fat and enable fat to be uniformly dispersed in water as an emulsion.
• An emulsifier has a water-loving hydrophilic head and an oil-loving hydrophobic tail.
• The hydrophilic head is directed to the aqueous phase and the hydrophobic tail to the oil phase.
• Water and oil, when mixed together and vigorously shaken, form a dispersion of oil droplets in water (or vice versa).
• When shaking stops, the phases separate.
• Adding an emulsifier keeps the droplets dispersed, and enables a stable emulsion.

Dispersion

• Water-insoluble fine powder like cocoa is difficult to disperse because small lumps tend to form on the surface of interface.
• Powders gradually aggregate and precipitate even after dispersing via shaking.
• Maintaining suspension of water-insoluble fine powder is called dispersion.
• When the dispersing material is liquid, this is termed an emulsion.

Stabilizers

• A stabilizer is an additive to food which helps preserve its structure.
• Stabilizer additions prevent oil/water emulsions from separating (e.g salad dressing).
• Stabilizers prevent ice crystals from forming (e.g ice cream).
• They stop fruit from settling in products (e.g jam, yoghurt and jelly).
• Common hydrocolloids used as stabilizers:
• Agar: jelly-like substance obtained from the cell walls of some red algae.
• Carrageenan: derived from red seaweeds.
• Cellulose/cellulose derivatives: derived from plant cell walls.
• Gelatin: derived from partial hydrolysis of collagen found in animal skin and bones.
• Guar gum: derived from seeds of guar plant.
• Pectin: derived from fruits (citrus and apple).
• Starch: derived from foods like grains (rice, wheat, corno tubers, potatoes, yams), and legumes.
• Xanthan gum: derived from fermenting sugars from bacteria Xanthomonas campestris.
• This bacterium is dried and ground into powder.
• Stabilizers and emulsifiers, are food additives to maintain the physicochemical state of a food product.
• Emulsifiers enable maintenance of a homogenous dispersion of two or more immiscible substances.
• Emulsifiers are fat-like substances found naturally in animal/vegetable fats and oils.
• Lecithin and monoglycerides are emulsifier forms.
• Lecithin is found in soy bean/eggs.
• Monoglycerides are found in soy bean, eggs and lard.
• Emulsifiers help mix ingredients that would normally separate (e.g., oil and water).
• Stabilizers prevent them from separating again.

Uses of Emulsifiers and Stabilizers in Food

• Stabilizers and emulsifiers have multifunctional properties when used in bakery products.
• They can also improve the quality/shelf life of bread products (buns, loaves, pastries).
• Emulsifiers in bakeries focus on starch and gluten proteins.
• Emulsifiers play a role in baked goods by improving loaf volume.
• This is due to their chemical structure.
• In dough, emulsifiers have positive effects on proof time, loaf volume and crumb firmness.
• This links to their ability to bind to the protein hydrophobic surface, promoting aggregation of gluten proteins.
• In bakery fillings, stabilizers deter water migration from the filling to the pastry due to their water-binding properties.
• Stabilizers appear to inhibit starch retro degradation and improve freeze-thaw stability of frozen dough, extending shelf life.
• Incorporation of stabilizers and emulsifiers in bread formulation improves bread-making.
• Emulsifiers play an important role in cake manufacturing and help to improve batter stabilization.
• Introducing an emulsifying agent into shortening enhances its emulsifying properties.
• This makes cake batter have a higher viscosity and greater stability.
• Air becomes more finely distributed within cake, resulting in a larger and moister cake.
• Emulsifiers are functional additives in chocolate and sugar confectionery products.
• They provide benefits during processing and storage.
• Emulsifiers promote breakdown into small fat globules in products containing a dispersed fat phase.
• They provide lubrication for ease in processing and consumption.
• Emulsifiers provide viscosity control and influence fat crystallization in chocolate and coating.
• This also improves the ease of handling and processability.
• Stabilizers and emulsifiers formulate functional dairy products.
• They prevent protein aggregation and dehydration.
• They improve the emulsion stability throughout the product shelf life.
• Stabilizers/emulsifiers improve the mouth-feel and creaminess of end products.
• They also improve appearance, body, texture and consistency of food products.
• Stabilizers and emulsifiers help formulate high-rheology products like yogurt, and flavored milk.
• These exhibit excellent texture and body, appearance, consistency and mouth-feel.
• Emulsifiers and stabilizers are important in making salad cream and mayonnaise (oil/water emulsions).
• They control separation of oil within mayonnaises/dressings, related to viscosity and suspending power.
• Stabilizers increase viscosity, increasing emulsion stability.
• Stabilizers improve the rheological and stability properties, provide superior suspension, cling, ease of mixing.
• Dressing stabilizers possess long-term acid stability, maintaining a steady viscosity over a range of temperatures.
• Margarine manufacturing balances the hydrophobic emulsifiers needed for processing and their hydrophilic emulsifiers that contribute to good qualities.
• Emulsifiers are used to give fine disperse and stable water and oil emulsions in margarine.
• Stabilization of low-calorie spread emulsions and using the right emulsifier make for stable spread.
• Low-fat margarine exhibits higher water content (than 80% margarine).
• The emulsifier used should be able to bind large amounts of water to obtain a product with longer shelf life.
• Adding emulsifiers helps products (peanut butter) inhibit oil phase separation.
• Stabilizers are important in water-binding capacity and sensory properties in margarine and spreads applications.
• Various stabilizer mixtures provide a range of stabilizer systems (binding free moistures).
• The incorporation of stabilizers results in a creamier and easy-to-use product.
• It also protects unsaturated oil from oxidation, thereby extending shelf life.
• The thickening or gelling effect of stabilizers and emulsifiers contributes to body and texture in ice cream.
• They influence texture and mouth-feel and can control the distribution of particles in a solution.
• Stabilizers have a high water-binding capacity, affecting rheological properties of an ice cream mix.
• Stabilizer incorporation in ice cream formulation leads to increased viscosity.
• Viscosity increase impacts the melting behavior of the product.
• Emulsifiers are used in ice cream.
• They contribute greatly to a smooth and creamy texture by promoting fat destabilization.
• Emulsifiers help destabilize fat globule membranes when homogenized.
• This promotes partial churning-out during freezing.

Lecithin

• Lecithin, a nonionic emulsifier, is one of the phosphoglycerides found in various plants and animals.
• It is found in substances like egg yolk, nerve tissue, semen, and cell membrane.
• Lecithin is a naturally occurring phospholipid derived from soybean and is both oil and water-loving.
• Lecithin is a vitamin and dietary supplement.
• It is an important component in cells.
• Lecithin can help nourish damaged cells/tissues and keep skin soft and supple.
• It is used to improve flow property of chocolate.
• Lecithin reduces cholesterol level and helps keep blood's cholesterol circulation freely.
• Lecithin holds fat and water together.
• Good Lecithin examples include soybean, egg yolk, mayonnaise, ice cream, lotion, cheese.

Soaps

• Soaps or detergents may be anionic, cationic and nonionic.
• Soaps are amphiphatic; part sticks to oil and part sticks to water.
• Oil attracts hydrophobic parts, and water attracts hydrophilic parts.
• Soap contains a non-polar tail and a polar or ionic head.
• The non-polar end of the molecule dissolves well in non-polar grease and oil.
• The polar or ionic head dissolves well in water.
• The tail of soap molecule penetrate into oil/grease and break it up into tiny micelles.
• Cationic soaps are quaternary ammonium salt of acetates, chlorides or bromides.
• Anionic soaps are sodium alkyl sulfates and sodium alkyl benzene sulfonate.
• Non-ionic detergents are esters of alcohol with high molecular mass Polyozyethylene fatty alcohol ethers.

Diacetyl Tartaric Acid Ester

• Diacetyl Tartaric Acid Ester (DATEM) is a non ionic emulsifier.
• DATEM strengthens dough by building a strong gluten network.
• DATEM is used in baking.
• It increases the physical volume of bread, improves tissue structure, prolongs shelf life and increases the soft feeling.
• DATEM may be used in crusty bread, in chew texture products, and in biscuits, coffee whitener, ice cream, and salad dressing.
• DATEM interacts with the hydrophobic part of gluten, helping protein unfold and form cross-linked structure.
• It is used as an emulsifier/dispersion agent, improving emulsification and the inter-miscibility of oil and water.
• DATEM is dispersive in hot water, soluble in oil, fat or some kind of organic dissolvent.
• It improves the taste of butter.

Gums

• Gum may be cationic, non-ionic or anionic.
• Xanthan gum is anionic (natural).
• Cationic guar gum (semi natural) is cationic and guar gum is nonionic ( natural).
• Gum contains hydrocolloids that bind, thicken and emulsify gluten free ingredient.
• Guar gum is an emulsifier, thickener and stabilizer, and is approved for use in a wide range of food, cosmetics and pharmaceuticals
• It thickens without application of heat

Emulsion Instability

• The instability of pharmaceutical emulsions can be classified as:
• Flocculation and creaming
• Coalescence and breaking
• Phase inversion
• Miscellaneous physical and chemical change

Emulsion Stability

• Flocculation involves small spheres of oil clump, which rise or settle in the emulsion more rapidly than individual particles.
• Creaming is the concentration of the floccules of the internal phase that form an upward or downward layer depending on the density of internal phase.
• Coalescence is the process by which emulsified particles merge forming large particles.
• Breaking is when oil separates completely from water (due to coalescence and creaming combined).

Uses of Emulsions

• In Agriculture:
• Used as delivery vehicles for insecticides, fungicides and pesticides.
• Allows chemicals to be diluted and provides improved spray ability.
• In Cosmetics:
• Allows dilution of active ingredients.
• It can be used as a delivery vehicle for hair and skin conditioning agents.
• Example: hair conditioners
• Surfactant:
• Reduces odor and flammability in applications such as paints and inks.
• Foods such as Milk , Salad Dressing,Gravies, Peanut Butter and Ice Cream.
• Fire Extinguishing involving flammable liquids.

Pharmaceutical Application

• Emulsions cover unpleasant tastes.
• They increase absorption rate.
• Topical emulsions are washable, and have acceptable viscosity.
• Emulsions are less greasy, provide controlled drug release and increased bioavailability.
• They protect thermolabile drugs and reduce patients variability.

Storage and Packaging

• Depending on use, emulsions should be packed in suitable containers.
• For oral use, they should be packed in well-filled bottles with air tight closure.
• Light-sensitive products should be packed in amber colored bottles.
• For viscous emulsions, wide-mouth bottles should be used.
• The label should mention shaking well before using.
• External use products must clearly state "external use" on their label.
• Emulsions should be stored in a cool place; refrigeration should be avoided.