The Anatomy of a Durable Emulsion

An emulsion can look excellent on the day it is made. The harder test comes after.

In a finished beverage, the concentrate is diluted hundreds of times. The pH drops. Acids, salts, sweeteners, and flavor oils may enter the system, and the droplets find themselves in a very different environment from the one they were manufactured in. Then, the can spends weeks or months in warehouses, trucks, and retail coolers.

Our last post defined the challenges that oil droplets face following the transition from a concentrated emulsion to a beverage. This post looks at the measurements we use to confirm that the emulsion holds up against those challenges.

No single analytical number provides the answer. Particle size, size distribution, zeta potential, interfacial behavior, and potency each examine a different part of the system, and each presents a limited viewpoint alone. The strongest evidence comes when several measurements point the same way and the finished beverage behaves accordingly. That is how we evaluated L04, a three-emulsifier system designed with multiple lines of defense to withstand the beverage challenge.

1. Start with the droplets

Measurement: Dynamic light scattering (DLS) | L04 average: 254.6 nm

DLS sizes droplets by tracking how quickly they drift through a liquid. Our manufacturing target is 250 to 275 nm, and L04 measures 254.6 nm on average.

To an extent, droplet size matters on its own because creaming, the density-driven rise of oil droplets toward the top of a container, slows as droplets get smaller. Size tracked over time is a more revealing indicator: droplets hold their initial size through shelf life only if the stabilization system is robust enough to keep them there. For example, droplets may grow via Ostwald ripening, a phenomenon in which oil gradually leaves small droplets, travels through the surrounding water, and joins larger ones. Formulation strongly influences how fast ripening proceeds. The makeup of the oil phase and the interfacial layer around each droplet both matter, and a well-designed system can slow it enough that little change is measurable over a product’s storage life. A single measurement shows where an emulsion starts; repeated measurements show whether ripening or other processes are changing it.

Day 0 size is therefore a starting point. We treat particle size as a trajectory rather than a snapshot. In concentrated L04 emulsion stored at ambient temperature, average size moved 3.7% over six months.

The more telling result came from a finished beverage. We tracked L04 against a single-emulsifier system for two months in a flavor-oil beverage, one of the most demanding matrices we test in. Flavor oils add a second oil phase to the beverage, which has the potential to disrupt a cannabinoid emulsion. For example, citrus oils move through water far more readily than cannabinoid oils, so they can ripen quickly and exchange material with the cannabinoid droplets. Some flavor components are also surface-active and compete with emulsifiers for space at the droplet surface. As with ripening generally, a well-designed system can hold these effects to a minimum, and L04 was designed with high flavor loads in mind. L04 stayed within 2% of its baseline size over two months of ambient storage. The single-emulsifier system grew 19%, most of it in the first week. Under the conditions tested, that gap says more about the two formulations than either one’s starting size.

2. Then look at the population

Measurement: Polydispersity index (PDI) | L04: 0.133

Two emulsions can share an average size and have very different size distributions. PDI measures that distribution’s width: values near 0 mean nearly uniform droplets, higher values indicate a broader mix. With a PDI of 0.133, L04 has a relatively narrow population by emulsion standards. Its favorable average comes from an evenly sized population rather than from a blend of very small and very large droplets.

Instability is often a population phenomenon. Droplets flocculate, coalesce, cream, and exchange oil through ripening, and a distribution that broadens over time can signal those changes before anything is visible in the can. A narrow starting distribution has few of the large droplets that cream fastest and collide most often, and a well-designed formulation keeps the population narrow as the product ages. We use PDI for what it measures directly, which is uniformity at formation and change over time. A narrow distribution held alongside a stable size is one more sign the emulsion structure is being preserved.

3. Ask how strongly the droplets interact

Measurement: Zeta potential by electrophoretic light scattering (ELS) | L04: −44.4 mV

Zeta potential reflects the effective charge at a droplet’s surface, measured by how fast droplets move in an electric field. It describes the emulsion’s capacity for electrostatic repulsion: a mechanism that keeps the emulsion from clumping together because droplets carrying the same charge repel each other. A widely used rule of thumb holds that magnitudes around 30 mV or above suggest meaningful electrostatic stabilization. L04’s zeta potential value indicates substantial negative charge under our measurement conditions.

Real-world beverage conditions like acidity, ionic strength, and presence of electrolytes or minerals dampen this effect, and a value measured on the emulsion will shift once it is diluted into an acidic, salt-containing drink.

For this reason, L04 was designed with more than one line of defense. Electrostatic stability is one of several mechanisms L04 uses to prevent droplet interactions. When a beverage weakens one mechanism, the others still work. For that reason, we test L04 under acidic, formulation-relevant conditions and do not rely on the charge measurement alone.

4. Challenge the interface

Measurement: Surface tension change by tensiometry | L04: +6.21 mN/m at pH 2.5 (single-emulsifier: +11.67 mN/m)

An oil-in-water emulsion exists because emulsifier molecules stabilize the boundary between oil and water. The interfacial layer is a few nanometers thick, but it largely decides whether droplets remain separate or begin interacting, aggregating, and ultimately separating.

Dilution into a beverage can change that equilibrium dramatically, as pH and ionic strength shift, and flavor constituents with their own surface activity compete for space at the interface. We used tensiometry in our stress testing program to evaluate L04’s system-level response to beverage-relevant challenges; low pH is one of the most common threats to emulsion stability. Under a defined pH 2.5 challenge, L04’s surface tension rose 6.21 mN/m, compared with 11.67 mN/m for the single-emulsifier benchmark. When faced with the same severe change in chemistry, L04’s multi-emulsifier system undergoes less measurable physicochemical change compared to the single-emulsifier system.

The evidence becomes stronger when the measurements agree

No individual measurement proves that an emulsion is durable. Instead, we look for convergence:

• L04’s droplets start in a controlled size range with a narrow size distribution.
• The system carries substantial electrostatic character under test conditions.
• Its measured surface-tension change in an aggressive acid challenge is about half that of a benchmark single-emulsifier system.

In a demanding finished beverage:

• L04’s droplet size held within 2% over two months while the comparison grew 19%.
• Potency held within 3% over three months at ambient temperature.

What we are building is a map of L04’s operating window. The design goal from the start was an emulsion that reacts as little as possible when the environment around it changes, through dilution, packaging, and storage. The analytical panel is how we check that goal against the data, and so far the measurements agree.

How we use accelerated testing

Accelerated stability testing is useful, and we use it: 40°C at 75% relative humidity. Four weeks under those conditions moved concentrated L04 particle size 2.2% and potency 2.6%. We report that as four weeks at 40°C.

Converting accelerated timelines into months of ambient shelf life would require knowing that heat speeds up the relevant failure modes in a predictable way. For a complex emulsion, that has to be demonstrated, not assumed. Oxidation, flocculation, coalescence, ripening, and interfacial rearrangement can each respond to temperature differently, and heat can change how emulsifiers behave in ways that never happen at room temperature. Pharmaceutical stability guidelines (ICH), which are not beverage standards, reflect the same caution and rest extrapolation on real-time data. We use accelerated results to compare formulations and find vulnerabilities, and we let real-time data speak to shelf life.

Request the Full Technical Deck

The L04 Product Information Deck contains the underlying studies, conditions, replicate details, and trend charts. For formulators and QA teams, we can also review the data against your own beverage matrix. Contact hello@perfectlydosed.com.