Emulsion-Based Extract Stability Testing Service

Emulsion-based delivery systems are one of the most technically complex formats in cosmetic and nutraceutical product development. These systems encapsulate lipid-soluble active ingredients such as Curcuminoids, Coenzyme Q10 (CoQ10), Vitamin D3, Astaxanthin, CBD, Resveratrol, and Quercetin within a carrier that improves their bioavailability, solubility, and skin or gastrointestinal permeation. Product types include Nano-emulsion with droplet sizes below 200 nm, Micro-emulsion with droplet sizes of 10 to 100 nm, Self-Emulsifying Drug Delivery Systems (SEDDS), Liposomes composed of a Phospholipid Bilayer, Solid Lipid Nanoparticles (SLN), and Nanostructured Lipid Carriers (NLC).

The physical instability challenges of emulsion systems in the hot and humid environment of ASEAN Zone IVb are distinctive from those of conventional cosmetic emulsions. Phase Separation, Coalescence, Ostwald Ripening, Sedimentation, and Creaming can all cause loss of product homogeneity and active ingredient content before the end of the declared shelf life. These changes are often not visible to the naked eye at early stages, making instrumental characterization essential for detecting stability issues before they become consumer-visible failures.

TIBD’s service is designed specifically for emulsion-based delivery systems, covering Particle Size and Polydispersity Index (PdI) by Dynamic Light Scattering (DLS), Zeta Potential by Electrophoretic Light Scattering (ELS), pH, Viscosity, Phase Separation assessment, Encapsulation Efficiency (EE%), Drug Release Profile, and Active Ingredient Assay by High Performance Liquid Chromatography (HPLC) under ASEAN Zone IVb conditions, in partnership with VISBIO as an Independent Quality Assurance Verifier (IQAV) using Validated Methods per ICH Q2(R1).

Six emulsion system architectures are applied in cosmetic and nutraceutical products, each with distinct stability characteristics and testing requirements.

• Macro-emulsion systems have droplet sizes in the range of 1 to 100 micrometres and appear turbid or opaque to the eye. These conventional emulsions are the most widely used format due to their manufacturing simplicity, but are the least thermodynamically stable and are most susceptible to Coalescence and Creaming during storage.
• Micro-emulsion systems have droplet sizes of 10 to 100 nm and are thermodynamically stable, forming spontaneously under appropriate surfactant conditions. They appear clear or slightly translucent. SEDDS (Self-Emulsifying Drug Delivery Systems) are oil-surfactant-co-surfactant combinations designed to self-emulsify upon dilution with gastrointestinal fluids, making them suitable for oral capsule formats delivering lipid-soluble actives such as CoQ10, Vitamin D3, and CBD.
• Nano-emulsion systems have droplet sizes of 20 to 200 nm and are produced by high-energy processing methods including High-Pressure Homogenization (HPH), Ultrasonication, and Microfluidization. Unlike Micro-emulsions, Nano-emulsions are kinetically stable rather than thermodynamically stable, and require ongoing monitoring of particle size and PdI throughout the shelf life to confirm that the nano-scale droplet distribution is maintained.
• Liposome systems are Phospholipid Bilayer Vesicles with sizes of 50 to 500 nm that encapsulate active ingredients in an aqueous core or within the bilayer membrane, depending on the hydrophilic or lipophilic character of the active. Liposomes are widely used in cosmeceutical and pharmaceutical products for their biocompatibility and skin permeation-enhancing properties, but require controlled storage temperature to maintain bilayer integrity.
• Solid Lipid Nanoparticles (SLN) use a solid lipid matrix that is in solid state at room temperature, providing improved active ingredient protection against oxidation compared to liquid emulsion systems. Nanostructured Lipid Carriers (NLC) use a mixed matrix of solid and liquid lipids, which improves loading capacity for high-concentration actives and reduces expulsion of the active ingredient from the matrix during storage, a phenomenon known as Polymorphic Transformation.

Six instability mechanisms specific to emulsion systems must be addressed in a stability protocol designed for ASEAN Zone IVb conditions.

Phase Separation is the most fundamental thermodynamic instability of oil-water systems. When an emulsion separates into distinct oil and water phases, the product is no longer fit for use and active ingredient homogeneity is lost. Phase Separation assessment at each Pull Point by visual examination and, for nano-scale systems, by Turbidity measurement, is a primary stability criterion.

Coalescence is the merging of smaller droplets into progressively larger droplets, driven by reduction of the total oil-water interface area. Coalescence is detected by an increase in Z-Average particle size and an increase in PdI over the study period. Nano-emulsions showing consistent particle size growth over the first three months of accelerated testing are at risk of visible Phase Separation before the end of the declared shelf life.

Ostwald Ripening is a mechanism specific to polydisperse nano-scale systems, where larger droplets grow at the expense of smaller droplets through molecular diffusion of the dispersed phase through the continuous phase. This is the primary growth mechanism in Nano-emulsions when Coalescence has been suppressed by a robust surfactant film. Ostwald Ripening rate increases at elevated temperatures, making Accelerated Stability testing conditions of 40°C / 75% RH particularly informative for predicting long-term particle size stability.

Sedimentation and Creaming occur when the density difference between dispersed and continuous phases drives droplet migration under gravitational force. For nano-scale systems, Brownian motion generally counteracts this, but in Macro-emulsion and unstable Nano-emulsion systems, Creaming (upward migration of oil droplets) or Sedimentation (downward migration of denser particles) causes visible separation within the shelf life.

Zeta Potential is the electrostatic surface charge of the droplet, measured by Electrophoretic Light Scattering (ELS). An absolute Zeta Potential value of 30 mV or greater indicates sufficient electrostatic repulsion between droplets to resist Coalescence. Values approaching zero indicate loss of electrostatic stability and predict imminent phase separation.

Active ingredient degradation through oxygen permeation, light exposure, and water penetration into the lipid matrix is the primary chemical instability mechanism for emulsion-encapsulated actives. Astaxanthin, Curcuminoids, CoQ10, and Resveratrol are particularly susceptible to oxidative degradation. The protective effect of encapsulation compared to the free active ingredient in solution must be quantified by comparing active content stability data from both systems throughout the study.

TIBD’s stability testing protocol for emulsion systems covers the full set of instrumental and physicochemical parameters required to characterize droplet population stability and active ingredient integrity.

• Particle Size (Z-Average) and Polydispersity Index (PdI) are measured by Dynamic Light Scattering (DLS) using a Zetasizer or equivalent instrument. For Nano-emulsion systems, the acceptance criterion is typically PdI not more than 0.3, indicating a sufficiently narrow droplet size distribution. An increase in Z-Average of more than 20% from the initial value, or PdI exceeding 0.3, indicates physical instability of the colloidal system.
• Zeta Potential is measured by Electrophoretic Light Scattering (ELS). The acceptance criterion for colloidal stability is typically an absolute Zeta Potential value of 30 mV or greater. A shift toward zero indicates reduced electrostatic repulsion and increased Coalescence risk.
• pH is measured by pH Meter at each Pull Point. The acceptance criterion is typically plus or minus 0.5 units from the initial value. pH change in emulsion systems can indicate hydrolysis of Phospholipid components, particularly in Liposome systems where Lysophospholipid formation changes both the pH and the bilayer integrity.
• Viscosity is measured by a Viscometer or Rheometer. The acceptance criterion is typically within plus or minus 20% of the initial value. Viscosity change indicates structural changes in the continuous phase polymer or emulsifier network that affect product texture, pourability, and droplet stabilization performance.
• Turbidity and Optical Clarity are assessed by visual examination under standardized lighting and by Turbidimeter or Spectrophotometer measurement. For products that must remain clear (Micro-emulsions and SEDDS), development of turbidity indicates droplet size growth beyond the sub-100 nm range where the system was initially clear.
• Centrifugation Stress Testing at 3,000 to 5,000 rpm for 30 minutes serves as an accelerated physical stability screening tool. Phase Separation observed after centrifugation indicates a formulation stability issue that will likely manifest during the long-term stability study, allowing early formula optimization before committing to a full stability study.

Encapsulation Efficiency (EE%) quantifies the proportion of the active ingredient that is successfully encapsulated within the emulsion droplet, relative to the total active ingredient in the system. The complementary parameter, Drug Loading (DL%), expresses the mass of active ingredient per unit mass of carrier system. Both parameters are measured at T0 and monitored throughout the stability study to confirm that the encapsulation system retains its loading capacity.

• EE% is measured by separating the free (unencapsulated) active from the encapsulated fraction using Ultrafiltration, Centrifugation, or Dialysis, then quantifying the free fraction by HPLC. A decrease in EE% during storage indicates that the active ingredient is migrating out of the encapsulation system, either through leakage from Liposome bilayers or through Ostwald Ripening-driven expulsion from lipid droplets.
• Drug Release Profile is assessed by the Dialysis Bag method or Franz Diffusion Cell, which separates the emulsion from a receptor medium by a semi-permeable membrane and measures the rate at which the active ingredient crosses the membrane over time. For oral delivery systems, In-vitro Dissolution testing in Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF) per USP or Ph.Eur. methods provides data supporting bioavailability claims.
• For topical delivery systems, Skin Permeation Testing using a Franz Diffusion Cell with a Synthetic Membrane (Strat-M) or Excised Skin provides comparative data on penetration enhancement relative to a non-encapsulated control formulation. This data supports claims that the emulsion delivery system improves skin delivery of the active ingredient relative to a conventional formulation.

TIBD and VISBIO apply compound-specific HPLC methods validated as Stability Indicating methods, capable of separating the active ingredient from its degradation products.

• Curcuminoids (Curcumin, Demethoxycurcumin, Bisdemethoxycurcumin): Analyzed by HPLC with UV detection at 425 nm using a Stability Indicating Method that separates all three curcuminoid compounds. Each compound has a distinct stability profile: Curcumin is the most abundant and most extensively studied, while Demethoxycurcumin and Bisdemethoxycurcumin have different degradation kinetics under acidic and oxidative conditions.
• Coenzyme Q10 (CoQ10, Ubiquinone): Analyzed by HPLC with UV detection at 275 nm, or by Electrochemical Detection for higher sensitivity at trace concentrations. CoQ10 degrades through oxidation to Ubiquinol and further degradation products. The HPLC method must resolve CoQ10 from its oxidized forms to function as a Stability Indicating method.
• Vitamin D3 (Cholecalciferol): Analyzed by HPLC with UV detection at 265 nm. Due to the typically low concentration of Vitamin D3 in emulsion systems (400 to 2,000 IU per dose), sample pre-concentration is generally required.
• Astaxanthin: Analyzed by HPLC with Photodiode Array (PDA) detection at 478 nm. The method must resolve and quantify both Cis and Trans isomers of Astaxanthin, as isomerization is a primary degradation pathway under thermal and light stress conditions. Total Astaxanthin content is reported as the sum of all isomers.
• CBD (Cannabidiol): Analyzed by HPLC with PDA detection at 220 nm using a method that separates CBD from CBDA (Cannabidiolic Acid), CBN (Cannabinol), and THC (Tetrahydrocannabinol). Separation from THC is required to confirm legal compliance in markets with THC concentration limits.
• Resveratrol: Analyzed by HPLC with UV detection at 306 nm. Trans-Resveratrol is the biologically active form; isomerization to Cis-Resveratrol under UV exposure is a primary degradation pathway and must be resolved in the Stability Indicating method.
• Quercetin: Analyzed by HPLC with UV detection at 370 nm.

All active ingredients must be maintained at Not Less Than 90% of the initial declared value throughout the stated shelf life. For actives with high susceptibility to degradation under ASEAN Zone IVb conditions, manufacturers should validate the protection factor of the encapsulation system by comparing active content stability in the emulsion versus the free active in solution under identical test conditions.

Long-term Stability testing uses 30°C / 75% RH conditions per ASEAN Zone IVb for a minimum of 24 months. Accelerated Stability testing uses 40°C / 75% RH for 6 months, providing early prediction of long-term stability and supporting shelf life claims via ICH Q1E extrapolation.

Cycling Test between 4°C and 45°C for 3 to 6 cycles simulates temperature fluctuations experienced during transport and distribution in the ASEAN supply chain, where cold chain management may be inconsistent. A single temperature cycle is particularly informative for Nano-emulsion systems, as repeated transitions through the lipid melting point can accelerate Ostwald Ripening and Polymorphic Transformation in SLN and NLC systems.

Centrifuge Stress Test at 3,000 to 5,000 rpm for 30 minutes is conducted as an accelerated physical stability screening tool at T0 and at each Pull Point. Results are assessed alongside DLS particle size data to distinguish mechanical phase separation from thermal instability.

Standard Pull Points for Long-term testing are at months 0, 1, 3, 6, 9, 12, 18, and 24. Standard Pull Points for Accelerated testing are at months 0, 1, 2, 3, and 6.

For Liposome and Nanoparticle systems that require controlled cold storage, a Cool Storage condition of 5°C plus or minus 3°C is included in the protocol alongside the standard Zone IVb conditions, to confirm that the product remains stable under the recommended cold chain storage temperature throughout the shelf life.

Beyond stability testing, TIBD provides formulation design consultation for manufacturers seeking to develop a commercially robust emulsion system for their active ingredient.

• Emulsifier system selection is the primary determinant of emulsion stability. Common emulsifiers used in food-grade and cosmeceutical emulsion systems include Polysorbate 80 and Polysorbate 20, Lecithin (both soy and sunflower sources), Sucrose Ester, Sodium Caseinate, and Whey Protein Isolate (WPI). Each emulsifier has a characteristic Hydrophilic-Lipophilic Balance (HLB) value that determines the type of emulsion it stabilizes, and emulsifier blends are designed to achieve the target HLB for the specific oil-water ratio of the formulation.
• Co-surfactants including Glycerin, Propanediol, and Ethanol are added at appropriate concentrations to reduce interfacial tension and stabilize the emulsifier film around each droplet.
• Stabilizers including Xanthan Gum, Carrageenan, and Pectin are used to increase the viscosity of the continuous phase and reduce droplet mobility, slowing Coalescence and Creaming without affecting the droplet size distribution.
• High-energy manufacturing methods including High-Pressure Homogenization at pressures above 500 bar, Microfluidization, and Ultrasonication are used to achieve nano-scale droplet sizes that cannot be produced by conventional mixing. The process parameters must be optimized for each formulation to achieve the target particle size and PdI while maintaining active ingredient integrity.
• Surfactant concentration must be balanced against Cytotoxicity concerns. At high concentrations, Polysorbate 80 and other nonionic surfactants can disrupt cell membranes, which is a safety concern for topical products applied near the eye area and for oral delivery systems. The surfactant concentration in the final formulation must be below the accepted safety thresholds while remaining sufficient to maintain the required emulsion stability.
• Packaging for emulsion systems should use amber glass bottles or opaque packaging to protect light-sensitive actives such as Astaxanthin, CoQ10, and Resveratrol from photodegradation. Air-tight closures with induction sealing or nitrogen headspace flushing reduce oxygen ingress during storage. Pump dispensers that do not allow air backflow into the bottle are recommended for emulsion products containing oxidation-sensitive actives.

The analytical credibility of emulsion stability data depends on the independence and technical capability of the testing laboratory. VISBIO, acting as an Independent Quality Assurance Verifier (IQAV), conducts Particle Size and PdI by DLS, Zeta Potential by ELS, Encapsulation Efficiency assessment, Active Ingredient Assay by HPLC, and Drug Release testing on samples collected at TIBD’s Pull Points, using Validated Methods per ICH Q2(R1) with full traceability documentation at every step and operations conducted under ISO/IEC 17025 standards.

For emulsion products intended for export or for submission to regulatory authorities requiring independent third-party analytical data, VISBIO’s role as an independent IQAV provides the documentary credibility that import partners and regulatory reviewers expect from Thai manufacturers competing in the international cosmeceutical and nutraceutical market.

The Emulsion-Based Extract Stability Testing service is conducted in partnership with Dr. Wuttipong Panitsettakorn, Advisor and Co-Founder, who specializes in commercial technology management for the health and beauty industry. Our team includes researchers specializing in Pharmaceutical Nanotechnology, Colloidal Science, and Drug Delivery Systems, with specific expertise in DLS and ELS characterization, Encapsulation Efficiency methodology, Drug Release modeling, and Stability Indicating HPLC method development for lipid-soluble active ingredients.

Is your emulsion-based product ready for Thai FDA registration or for export to ASEAN and international markets? If you need stability data covering Particle Size by DLS, Zeta Potential, Encapsulation Efficiency, Drug Release Profile, and Active Ingredient Assay by HPLC for your Nano-emulsion, Micro-emulsion, SEDDS, Liposome, or SLN/NLC system, contact TIBD for a customized protocol and starting price from ฿15,000.