Types, Uses and Components of Emulsifiers

Emulsifiers: Types, Uses and Components

Introduction

This article contains everything you will need to know about emulsifiers and their use.

You will learn:

What is an Emulsifier?
Types of Emulsifiers
Uses for Emulsifiers
Components of an Emulsifier
And much more …

Chapter 1: What is an Emulsifier?

An emulsifier is a specialized device designed to create stable emulsions by dispersing droplets of liquids that do not naturally mix, using an emulsifying agent. This device supports the mixing of liquids or solutions that would typically separate after being combined. During the emulsification process, the liquid is broken into very small droplets or particles, employing techniques such as rotating propeller mixers, vacuum systems, rotor-stator arrangements, and high shear mixers. These processes reduce droplet sizes to less than one micron (µ), forming a finely textured emulsion. Emulsifiers use high-pressure methods to achieve the necessary droplet dimensions.

There are various types of emulsifier machines or vacuum emulsifying mixers that can mix, disperse, homogenize, emulsify, and aspirate both viscous ingredients and immiscible liquids. These machines are engineered with a construction that prevents dead zones and operate electronically. They also have the capability to emulate a vacuum and manipulate temperatures by heating or cooling the environment. Emulsifiers are frequently employed to mix products like creams, lotions, ointments, medications, and liquid creams, thanks to their expertise in handling substances that don't naturally blend.

Chapter 2: What is the process of emulsification?

Emulsification aims to produce the smallest possible droplet size so that immiscible materials can blend into a stable emulsion. By increasing the energy input into the mixture, smaller droplets are generated, leading to a finer emulsion. The efficiency of the emulsion process significantly influences the consistency and quality of the final product. Although various synthetic agents can be used to achieve emulsification, a mixer proves to be more effective in attaining the desired droplet size.

Emulsification involves a two-phase system where one phase, known as the internal or dispersed phase, is transformed into tiny droplets and dispersed within the other phase, called the external or continuous phase. Energy is necessary to create this emulsion and establish the two-phase system.

The objectives of emulsification include:

Physicochemical Stability – Emulsification determines the characteristic structure of a product.
Sensory Properties – Emulsification determines the appearance, texture, and flavor of a product.
Surface – The careful mixing of two immiscible, non-soluble substances produces an even, smooth surface.

Emulsification is the process where one immiscible liquid is dispersed within another immiscible liquid. Unlike colloidal solutions, which involve particles dispersed in a liquid, emulsification specifically pertains to the mixing of liquids. This process involves a combination of chemical, physical, and mechanical methods.

Mechanical emulsification relies on three fundamental theories:

Surface Tension Theory – Surface tension theory postulates that emulsification takes place when there is a reduction in the interfacial tension between the dispersed phase and the dispersion medium.
Repulsion Theory – In repulsion theory, the particles of the dispersed phase remain dispersed in the dispersion medium, which is caused by repulsion force. A film covers one phase, which makes globules of that phase repel other globules.
Viscosity Modification – Emulsifying agents can increase the viscosity of a medium causing the globules of the dispersed phase to remain dispersed in the dispersion medium.

Types of Emulsion

Emulsions are categorized into simple and complex types. Simple emulsions involve either oil dispersed in water or water dispersed in oil. When water is the dispersed phase and oil is the continuous phase, the emulsion is termed water-in-oil (W/O). Conversely, if oil is dispersed in water, it is called oil-in-water (O/W).

Complex emulsions, also known as multiple emulsions, include both oil-in-water and water-in-oil emulsions, often stabilized by surfactants. These are denoted as O/W/O and W/O/W, representing double emulsions of O/W and W/O types.

Emulsifiers

Emulsifiers act as stabilizing agents in emulsions by enhancing kinetic energy. They typically feature both hydrophilic (water-attracting) and hydrophobic (water-repelling) components. Common emulsifiers include Lecithin, soy lecithin, sodium phosphates, monoglycerides, diglycerides, and sodium stearoyl lactylate.

Emulsification Process

While emulsification is widely utilized in food production, its applications extend to various industries, including pharmaceuticals and paints. This process enables the creation of diverse products by blending ingredients and liquids in innovative and unconventional methods.

Emulsifier – The key to emulsification is the emulsifier, which is a surfactant that reduces the surface tension of liquids. Emulsifiers are carefully chosen to match the chemical properties of the ingredients to be combined such that they don’t precipitate out of the mixture.
Force – As may be expected, some type of force is necessary in order to blend and mix the liquids. There are a wide range of emulsifiers that provide the necessary energy and vary from blenders to powerful industrial machines and mixers.
An essential part of the emulsion process is stabilization, which is especially true for pharmaceuticals. Most emulsions are thermodynamically unstable and will separate over time. This aspect of emulsions necessitates the proper choice of an emulsifier to ensure long lasting stability.

The use of force or energy is due to emulsification rarely being a spontaneous process and requires energy in the form of mechanical shear that is provided by a mixer or blender. The final droplet size is dependent on the amount of energy that is applied. Paddle mixers are used when the droplet size is greater than 10 µ. To make smaller droplets, high shearing is required using rotor stator mixers.

Diagram of Cross Section of a Rotor Stator Head

Lipophilic and Hydrophilic Emulsifiers

Unlike the blending technique for combining two non-mixable liquids, emulsifiers that are lipophilic and hydrophilic are utilized to extract excess emulsifiable penetrants from the surfaces of treated components. These emulsifiers lack surfactants, making them particularly effective for removing surplus penetrants while keeping the desired penetrants intact on the part's surface.

Lipophilic emulsifiers interact with oil-based penetrants, allowing them to be removed from the component's surface with a water spray. They penetrate the residual emulsifiable penetrant and are quickly drained away from the part. This swift process is crucial to avoid over-emulsification and excessive removal of the penetrant.

Hydrophilic emulsifiers come in a concentrated form, which is diluted with water and employs detergent properties. Before applying the hydrophilic emulsifier, parts are first rinsed with water. Then, they are either submerged in agitated tanks containing the emulsifier or the emulsifier is applied via spraying. Following this, the parts are rinsed again with water.

Laser Diffraction

Laser diffraction is employed to assess the size of droplets generated during the emulsification process. This technique is crucial for defining various aspects of food products, including flavor, stability, appearance, and overall process efficiency. The method relies on the principle that the angle at which laser light is diffracted by a particle is indicative of its size. When particles of varying sizes are present, a distinct diffraction pattern emerges. Analyzing this pattern enables the determination of particle sizes. Following pattern analysis, an algorithm processes the data to compare the measured values and determine the distribution of particle sizes.

Chapter 3: What are the different types of emulsifiers?

Emulsification necessitates the application of energy in various forms. While the process involves specific chemical procedures, the mechanisms and energy sources used can vary widely. These may include the use of vacuums, ultrasonic waves, and advanced, high-efficiency equipment.

Rotor Stator Mixers

The emulsification process involves breaking down liquids into fine droplets to achieve effective mixing. Rotor-stator mixers are utilized to achieve high-speed dispersion. In this method, the rotor spins at high speeds, functioning like a centrifugal pump that draws in the material and fragments it into smaller particles.

Rotor-stator mixers operate in two distinct modes: batch and continuous. In the continuous mode, the blending process is uninterrupted, whereas the batch mode uses both pumping and shaft power. During emulsification, the mixture is pumped through a narrow gap in a perforated cylinder or stator, with the rapidly rotating rotor applying force to reduce droplet size.

Rotor-stator mixers are designed to create significant stress and intense turbulence. The rotor's energy is transferred to the stator, resulting in high local energy dissipation, which differs from conventional mixers. These mixers produce shearing stress, elongation stress, and turbulence cavitation to achieve very small particle sizes.

Micropore Emulsification

Micropore emulsification achieves more uniform droplet sizes and creates emulsions with exceptional stability. This technique is effective even with high-viscosity ingredients, ensuring the production of consistent and reliable emulsions. In this process, the two phases are combined under precise conditions. The dispersed phase is introduced through pores in a stainless-steel membrane, forming perfectly spherical droplets within the continuous phase.

The controlled shear forces cause the droplets to deform, separate from the membrane surface, and form droplets of the desired size. By regulating the size and movement of the droplets, this method ensures thorough mixing of each batch with minimal waste.

Diagram of the Micropore Emulsification Process

Ultrasonic Emulsifier

Ultrasound acoustic cavitation is used to disrupt oil and water droplets, creating both oil-in-water (O/W) and water-in-oil (W/O) emulsions with droplets in microns and nanosizes. The extremely small size of these droplets allows them to quickly penetrate cells. Nanoemulsions, which are essential for producing coatings, paints, and polymers, offer greater stability and are resistant to issues like sedimentation, coalescence, or flocculation.

Ultrasonic emulsification involves highly vigorous mixing that accelerates the emulsification process. This method thoroughly disperses one liquid into another, ensuring that neither liquid reverts to its original state. It is an advanced technique that employs surfactants to aid in the emulsification, making it a sophisticated method for achieving fine and stable emulsions.

High Pressure Homogenization

High pressure homogenizers are also capable of producing nano sized droplets. In the process, emulsion phases are pumped together under high pressure through a small volume orifice. The phases are placed in a tank where pressure is applied to force the liquid through an orifice or membrane that has a narrow slit. The action causes shearing and cavitation that homogenizes the phases. In some instances, the stream is directed at a blade, ring, or plate where the sample collides at high speed.

Unlike ultrasonic emulsifiers, which are limited in their capacity to handle large volumes, high-pressure emulsifiers are designed to process substantial quantities of liquids, making them ideal for applications in the dairy industry. Additionally, high-pressure homogenizers offer the flexibility to adjust the processing stream as needed.

High-pressure homogenizers are quite costly, with the most affordable models starting around $10,000. This high cost is justified by their suitability for large-scale production. To ensure cleanliness and prevent contamination, which is crucial in dairy production, these emulsifiers must be thoroughly cleaned after each use.

There are various types of high-pressure homogenizers, and choosing the right one requires careful consideration. Some models are designed for batch processing, while others support continuous processing, so not all high-pressure emulsifiers offer both options. Additionally, different homogenizers can handle a range of sample sizes, so it's essential to select a model that matches the requirements of the intended industry application.

While both homogenization and emulsification involve mixing to achieve specific properties, they differ in the nature of the solutions they handle. Homogenization involves blending two miscible liquids, whereas emulsification is used to mix two immiscible liquids.

High Shear Mixers

High shear mixers are rotor stator mixers, shear reactors, and shear homogenizers that are used for emulsification. They have high rotor tip speeds, high shear rates, localized energy dissipation rates, and a higher power consumption rate than ordinary mixers. Shearing is the stress that the blades or impellers of a mixer place on a liquid. The rotor directs a liquid outward to the stator, which creates a shear in the process. Variable speeds of the rotor make it possible to tailor the amount of shearing energy required to meet the needs of an application. The term shear is a reference to the stress placed on immiscible liquids by the mixing blades or impellers.

In contrast to high-pressure homogenizers, which use significant energy to apply pressure for reducing droplet size through emulsification, high-shear mixers achieve similar results through shearing action. These mixers efficiently reduce droplet sizes to the submicron level using mechanical shear forces.

High Speed Shear Mixer Dispersion Emulsifier

Inline Emulsifier

An inline emulsifier is a specific type of high-shear mixer featuring a rotor and stator assembly. Similar to rotor-stator mixers and other high-shear mixers, the rotor operates at high speeds to pull immiscible liquids through the stator. This process subjects the liquids to intense shearing forces, leading to the dispersion of tiny droplets throughout the mixture. The result is a highly stable emulsion.

Inline emulsifiers are available in various sizes and configurations to accommodate different application needs. Despite the variety of models, all inline emulsifiers share fundamental characteristics and features.

Shear Rate – The shear rate for an inline emulsifier is between 10,000 rpm up to 50,000 rpm.
Stages – The inclusion of multiple stages in an inline emulsifier makes it possible to have a more thorough emulsification process. Multiple shear forces are applied to the emulsion.
Cleaning – Inline emulsifiers have a clean in place system for easy cleaning of the mixing chamber to reduce downtime and increase productivity.
Efficiency – The key to the success of inline emulsifiers is their efficiency since they are a continuous emulsification process. They have an emulsification rate of over 90% to ensure cost-effective waste reducing processing.

Multi Shaft Mixer

Multi shaft mixers have more than one shaft and can include two, three, or four shafts. Their mixing elements can be blades, paddles, or have a helical shape, which are used in accordance with various applications. As with all forms of emulsification equipment, multi shaft mixers supply sufficient power to change droplet size for the emulsification process. They can handle a wide range of immiscible liquids efficiently and effectively and can be customized to the needs of any application.

A typical design for multi-shaft mixers features both a disperser and a rotor-stator within a single unit. This setup accelerates the emulsification process by having the disperser initiate the mixing, while the rotor-stator refines and enhances the texture of the resulting emulsion.

Vacuum Emulsifier

In a vacuum emulsifier, materials are placed in a mixing tank equipped with fixed impellers that feature perforations for effective mixing. During the emulsification process, the impellers rotate forward and backward at adjustable speeds. The forward rotation of one impeller pushes the materials upwards, while the reverse rotation of the other impeller drives them downward. This high-speed, bidirectional mixing ensures thorough blending. The finished emulsion is then extracted from the tank using centrifugal force.

The vacuum within the mixing tank is generated by a vacuum pump that removes air from the system. A sensor continuously monitors the pressure of the liquid to maintain optimal conditions. The vacuum enhances the mixer’s performance, preventing aeration, protecting the impellers, and ensuring a void-free final product.

Chapter 4: What are the uses of emulsifiers?

Emulsifiers play a vital role in numerous industrial processes by enabling the mixing of liquids to create various products. In manufacturing, certain products require the blending of ingredients with differing densities, which is achievable only with the use of an emulsifier. This component ensures that the ingredients remain stable until they are ready for final application.

The use of emulsifiers in the food, pharmaceutical, cannabis, and cosmetic industries is subject to the regulations set by the Food and Drug Administration (FDA), which oversees commercial products intended for public use. Any substance or material used in the production of these products must be approved by the FDA. For the food industry, acceptable emulsifiers include sorbitan esters and polysorbates derived from natural fatty acids.

Food Industry

Emulsifier machines and emulsifiers are extensively used in the food industry, as many food products are in an emulsified state, such as dressings, sauces, spreads, dips, creams, and beverages. Emulsifiers maintain ingredient stability, which helps extend the product's shelf life. The appropriate surfactant ensures that materials remain evenly mixed. In the meat industry, emulsifiers are employed to cut and mix meat for sausage production.

Pharmaceutical Industry

The pharmaceutical sector relies on emulsion technology to create palatable medications by better dispersing their ingredients. Without emulsification, drugs could be too bitter and ineffective, as dosages might become inconsistent. Emulsification blends and mixes ingredients to ensure medicines are produced with accurate proportions and dosages.

Cosmetics Industry

In the cosmetics industry, emulsions are crucial for achieving the desired appearance and ensuring even application of products. Emulsification breaks down substances into very small droplets, enabling the production of cosmetics with a smooth texture and ease of absorption. By significantly reducing particle size, emulsification enhances product stability and longevity.

Cannabis Industry

The cannabis industry benefits from emulsification by improving the flavor of its products. Emulsification ensures product consistency by reducing the size of cannabinoid molecules, facilitating better absorption by the body, and providing a uniform delivery of active ingredients.

Paint Industry

Paint consists of pigment, which provides color, a binder, and a solvent that keeps the paint liquid and spreadable. Emulsification is essential in paint production because the ingredients need to blend completely. The process involves dispersing the pigment and binder into the solvent, with the pigment and binder acting as oil and the solvent as water.

When paint is applied, the pigment and binder droplets coat the surface. As the solvent evaporates or dries, the droplets of pigment and binder consolidate and adhere to form a solid, colorful layer. This transformation is facilitated by the emulsification of the paint.

Industrial Lubricants

Metalworking fluids and industrial lubricants are typically oil-in-water (O/W) emulsions. Emulsifiers allow metalworkers to benefit from the lubricating properties of oil combined with the cooling effects of water. Anionic and nonionic emulsifiers are commonly used in metalworking, whereas cationic emulsifiers are less frequently used due to their instability in alkaline conditions.

Leading Manufacturers and Suppliers

Chapter 5: What types of emulsifiers are used in emulsification equipment?

Emulsifiers are crucial for the emulsification process, enabling the mixing and blending of immiscible substances. To effectively combine materials, an emulsifier that matches the chemical properties of the substances is required. During emulsification, the emulsifier lowers the interfacial tension between the materials and forms a film around the droplets. This action prevents the droplets from clumping together and helps maintain a consistent emulsion.

Anionic Emulsifier

Anionic emulsifiers dissolve in water to create hydrophilic groups. Suitable for alkaline or neutral conditions, they are not effective with acidic substances. These emulsifiers can be combined with nonionic types and are commonly found in products like laundry detergents, handwashes, kitchen cleaners, and body washes. They are also widely used in industrial applications such as architectural coatings, industrial coatings, and water-based coatings.

Cationic Emulsifiers

Cationic emulsifiers ionize in water to form cationic hydrophilic groups and are used with acidic compounds. They carry a positive charge and are effective in emulsifying water within oil-based coatings. Cationic emulsifiers are utilized in the production of wood finishes, metal coatings, and oil-based coatings.

Nonionic Emulsifiers

Nonionic emulsifiers are the second most commonly used type. Their molecules do not carry a charge. These emulsifiers are used to blend oils with water, in emulsion polymerization, and as dispersing agents in various applications. They are present in cleaning products, personal care items, and disinfectants. Nonionic emulsifiers do not ionize in water.

Sorbitan Monooleate

Sorbitan monooleate is utilized in food processing and is classified as a low polyol nonionic emulsifier in the lipophilic group. It serves as an additive in food and medicines, and is soluble in both water and ethanol. Sorbitan monooleate is employed as a stabilizer, dispersant, and emulsifier in the production and processing of food, medicines, cosmetics, and textile printing.

Lecithin

Lecithin, widely used in the food industry, is derived from sources such as soybeans, egg yolks, milk, sunflower seeds, and rapeseeds. It is often combined with other emulsifiers to form a mixed emulsifier that aids in stabilizing the emulsion process. Lecithin, available in liquid, granule, powdered, and gel capsule forms, is a versatile emulsifier with a broad range of applications.

Polysorbates

Polysorbates are derived from sugar alcohols found in fruits. They have a yellow hue and exhibit viscous properties after being processed with ethylene oxide.

Mono and Diglycerides

Mono and diglycerides, also known as partial glycerides, are fatty acids commonly present in food and are highly soluble in dense solvents.

Sodium Stearoyl Lactylate

Sodium stearoyl lactylate, derived from sodium salt, is a natural emulsifier approved by both the FDA and the EU.

Chapter 6: What are the best emulsifiers?

Sonolater from Sonic Corporation

The Sonolater is a high-pressure emulsifier designed to achieve extremely small droplet sizes through fluid acceleration, inline cavitation, and turbulent flow. It features a comprehensive system that includes a positive displacement pump, electric motor, and PLC controls. The Sonolater’s fixed orifice and blade are engineered to generate intense turbulence to break down oil phase droplets or deagglomerate solids within a liquid medium. It can be tailored to meet specific production requirements.

Vacuum Emulsifying Mixer from Makwell

The Makwell vacuum emulsifying mixer is equipped with a high-speed rotor and stator. As these components spin rapidly within the homo-head, a pressure differential is created between the mixer’s top and bottom. The material is processed through the homo-head, undergoing shearing, breaking, mixing, and emulsification. Once the upward force ceases, the emulsified material exits through the top of the head and is reintroduced by the downward pressure of the blades. The integrated vacuum system ensures smooth operation by preventing bubble formation.

High Shear Batch Mixer from Silverson

The high shear batch mixer from Silverson is designed to emulsify, homogenize, solubilize, suspend, disperse, and disintegrate solids. It features a rotor-stator work head that reduces processing time by 90%, enhancing quality, product consistency, and process efficiency. Capable of processing up to 8000 gallons (30283 L), this mixer excels in reducing particle sizes and producing highly stable emulsions. Its multistage mixing and shearing action allow efficient material processing through the work head.

Inline High Shear Mixer from Ross

The inline high shear mixer from Ross is utilized for reducing particle and droplet sizes to create emulsions that are scalable and reproducible. It includes a single, dual, or four-stage rotor-stator setup that mechanically shears materials as they pass by the stator. The mixer is either floor-mounted or placed on a platform, with materials gravity-fed into the mixing chamber. The rotor generates shearing force at speeds of up to 3000 to 4000 ft/min and expels the mixture through stator holes. It can handle high viscosity materials without needing a pump system.

Emulsifier and Inline Homogenizer Mixer from PerMix

The PerMix emulsifier and inline homogenizer mixer is a high-shear device designed for continuous inline operation. Its design allows easy integration into existing production lines through its inlet and outlet connections. For low viscosity liquids, it can pump materials without requiring an additional pump. Products can be processed in a single pass or circulated for multiple passes to achieve better quality. The PerMix mixer significantly reduces processing time, enhancing efficiency and lowering costs.

Chapter 7: What are some common problems with emulsification?

Given the complexity of the emulsification process, issues can arise. An emulsifier's role is to ensure the formation of a stable emulsion. The effectiveness of this process relies on the composition rate and the concentration of emulsifiers used. Factors that can lead to emulsion destabilization include coalescence, sedimentation, Ostwald ripening, creaming, flocculation, aggregation, and phase inversion.

Ostwald Ripening

Ostwald ripening occurs when smaller particles in a solution dissolve and deposit onto larger particles to achieve a more thermodynamically stable state. The molecules on the surface of smaller particles are less stable and dissolve, increasing the concentration of free molecules in the solution. Over time, this leads to the emulsion becoming unstable and eventually undergoing phase separation. Ostwald ripening typically happens in water-in-oil emulsions where oil molecules migrate through the water phase and coalesce with larger oil droplets.

Coalescence

Coalescence involves the merging of droplets into progressively larger droplets until the distinct phases of oil and water separate. This issue may arise from insufficient emulsifier levels, the precipitation of water-soluble emulsifiers, an excessive concentration of base or acid, or the use of incompatible anionic and cationic emulsifiers in the same mixture. Selecting an incorrect emulsifier can also contribute to this problem.

Flocculation

Flocculation happens when droplets clump together to form flocci. While clumping can be beneficial in some processes, in emulsions it leads to poor stability. This issue can be addressed by increasing agitation, boosting the concentration of the emulsifier, or incorporating a higher hydrophilic-lipophilic balance (HLB) emulsifier.

Sedimentation

Sedimentation, or creaming, occurs when less dense oil droplets rise to the top of the emulsion, forming a fatty layer. This can result from an imbalance in the size of the oil or water phases relative to each other, a small dispersed droplet size, or insufficient viscosity of the continuous phase. Adjustments can be made to rectify these issues and restore emulsion stability.

Conclusion

An emulsifier is an emulsion device used for colloidal dispersion of liquid droplets in immiscible liquids in the presence of an emulsifying agent. It enables the combining of non-soluble solutions or liquids that would normally separate during mixing.
The various types of emulsifier machines or vacuum emulsifying mixers can mix, disperse, homogenize, emulsify, and aspirate viscous ingredients and non-soluble liquids.
The goal of emulsification is to achieve the smallest possible droplet size. As more energy is applied to a mix, smaller droplets are produced in order to create a fine emulsion. A proper emulsion process can determine the consistency and quality of a product.
The types of emulsions are simple and complex where simple emulsions involve dispersing oil in water or water in oil. If the dispersed phase is water and the dispersion medium is oil, the emulsion is referred to as being water in oil or W/O. The reverse is true when the dispersed phase is oil and the dispersion medium is water, notated as O/W.
The emulsification process requires the use of some form of energy. Although the process of emulsification follows certain chemical steps, the types mechanisms and energy for the process take many different forms and involve the use of vacuums, ultrasonic waves, and high powered, high efficiency equipment.