How To Prevent Vegan Mayo From Breaking When Emulsifying? Choosing the Right Plant Protein for Emulsion Stability

Vegan mayonnaise seems straightforward at the onset: oil, water, an emulsifier, an acid. But the reality is rarely that rosy. That’s because the entire structure depends on a protein doing a job egg yolk used to do almost effortlessly.

Why Do Vegan Emulsions Separate in the First Place?

An emulsion is oil droplets suspended in water; without something coating those droplets, they find each other and merge: coalescence. In egg-based mayonnaise, phospholipids and proteins in the yolk wrap around each droplet and keep them apart. In a vegan system, a plant protein has to unfold at the oil-water interface, anchor itself there, and form a film strong enough to resist droplets colliding during mixing, pumping, and storage.

Not all plant proteins behave the same way at the oil–water interface. Under the processing conditions evaluated by Karefyllakis et al. (2023), a commercial soy protein isolate produced a slightly larger average droplet size (~60.0 μm) than a commercial pea protein isolate (~57.9 μm). [Since the comparison was limited to specific ingredients and processing conditions, the results should be viewed as formulation-specific rather than representative of all soy or pea proteins.] Smaller droplet size is often associated with improved emulsion stability because it reduces gravitational separation and increases total interfacial area available for protein adsorption. However, long-term stability also depends on interfacial film strength, continuous-phase viscosity, and electrostatic or steric repulsion between droplets.; more interfacial area for the protein film to distribute across, less driving force for droplets to merge, which is why droplet size, not just “does it look mixed,” is the metric to track from day one.

If an emulsion separates during processing, check droplet size before touching the formula, an oversized average droplet is often the first sign the protein isn’t anchoring efficiently.

Why Does Vegan Mayo End Up Too Thin, Too Thick, or Gummy?

Texture in mayonnaise comes from two systems working together: the protein stabilizing the interface, and a hydrocolloid (xanthan, guar, or a starch) building the continuous-phase viscosity that holds droplets in place. When formulators lean too hard on the hydrocolloid to compensate for a weak protein film, the product often turns gummy or pasty, because viscosity is compensating for insufficient interfacial stabilization. When protein is under-dosed relative to the oil load, the product turns thin and prone to oiling off during storage.

One approach that has received increasing attention is protein–polysaccharide conjugation, where a protein is chemically linked to a polysaccharide, such as xanthan gum or pectin, typically through a controlled Maillard reaction before being incorporated into the emulsion. Pea protein conjugated with xanthan gum has been used to develop plant-based mayonnaise with improved emulsion stability and interfacial performance (Choi et al., 2023). Rather than forming a separate “hybrid film,” these conjugates improve the protein’s ability to adsorb at the oil–water interface while providing additional steric stabilization and hydration around the droplets. This helps reduce droplet aggregation and can improve emulsion stability during processing and storage.

Why Do Pea and Soy Proteins Carry Off-Flavors?

Beany and grassy notes in pea and soy protein aren’t a sign of poor sourcing, they come from a well-characterized enzymatic pathway. Lipoxygenase, an enzyme naturally present in the seed, oxidizes polyunsaturated fatty acids like linoleic acid into hydroperoxides, which break down into volatile compounds such as hexanal and hexanol; the specific molecules responsible for the cut-grass and beany character formulators fight against (Vatansever et al., 2024).

This isn’t fixed at the point of extraction, it can keep developing during storage if lipid oxidation isn’t controlled, and it varies by growing conditions, not just by species. A multi-year study on pea protein isolates found that both harvest year and cultivation location significantly affected the concentration of volatile beany compounds in the finished protein, with seed age emerging as the dominant factor reducing lipoxygenase activity and polyunsaturated fatty acid content (Manouel et al., 2024). This may contribute to lot-to-lot sensory variation: two lots of the “same” pea protein, from different harvests, can carry meaningfully different flavor loads, part of why masking strategies alone are an incomplete fix.

If flavor shifts between lots with no process change, ask the supplier about harvest-year and growing-region variability before assuming the masking system failed.

Why Won’t Some Proteins Dissolve Properly in Acidic, High-Fat Systems?

Mayonnaise sits at a low pH, typically 3.5-4.2, to meet food safety requirements. That range is a problem for many legume proteins because it often sits close to their isoelectric point; the pH at which the protein carries no net charge and its solubility collapses. Above and below that point, solubility recovers, but right at it, protein that should be dissolved and working at the interface instead aggregates and drops out of solution.

This has been demonstrated directly in pea protein systems, where reducing pH toward the isoelectric point produced a marked drop in gelation and emulsion stability, an effect also seen in soy protein systems under comparable conditions (Munialo et al., 2025). In practice, formulators experience this solubility collapse as graininess or a gritty mouthfeel, the protein hasn’t disappeared, it’s simply no longer functioning as an emulsifier at that pH.

Check a candidate protein’s solubility curve against the target pH before running a full trial. A protein that performs beautifully at pH 7 can fail completely at pH 4 if its isoelectric point sits in the working range.

Why Is Aquafaba So Hard to Standardize?

Aquafaba, the liquid left over from cooking chickpeas, has strong emulsifying and foaming properties and has become a common egg-yolk substitute in vegan mayonnaise. Its core limitation isn’t functionality, it’s consistency: composition varies by chickpea cultivar, cooking time, and cooking pressure, so the same recipe can behave differently every time a new lot arrives.

Researchers who tackled this directly found cooking parameters had a measurable effect on emulsion quality, within the experimental conditions evaluated; chickpeas steeped at 4°C for 16 hours, then cooked at 116°C and 75 kPa for 30 minutes, as producing the most consistent aquafaba for mayonnaise-grade emulsification (He et al., 2021). The same study found both freeze-dried and spray-dried aquafaba powders retained functional emulsifying capacity after rehydration, useful for anyone moving from wet aquafaba toward a shelf-stable, specified ingredient.

Standardizing cooking parameters upstream is more reliable than formulating around lot-to-lot aquafaba variability after the fact.

Why Does Shelf-Life Testing Keep Surfacing Oxidation and Texture Drift?

A well-stabilized vegan emulsion can still change during storage through two connected mechanisms: lipid oxidation of the oil phase and gradual changes in the structure and integrity of the interfacial protein layer. Legume protein isolates can introduce trace amounts of transition metals during ingredient production or processing. Under certain conditions, these metals can act as pro-oxidants, accelerating lipid oxidation in oil-in-water emulsions and contributing to off-flavors and reduced shelf life (Brüls-Gill et al., 2024).

In the experimental model studied by Brüls-Gill et al. (2024), non-adsorbed protein remaining in the aqueous phase appeared to slow lipid oxidation by binding some of these metal ions. While this finding suggests a potentially protective role under the conditions evaluated, its influence is likely to vary with the protein source, formulation, and processing conditions rather than applying universally across all plant-protein emulsions.

Shelf-life failures are not always caused solely by an unstable interface. If oxidation becomes a recurring issue, it is worth evaluating the ingredient’s trace metal content alongside factors such as oil quality, antioxidant strategy, homogenization conditions, oxygen exposure, packaging, and storage conditions before reformulating the entire emulsion.

Why Is It Hard to Hit Both Food Safety and Functional pH at the Same Time?

This challenge underlies almost every issue above. Regulatory guidance for shelf-stable mayonnaise-type products calls for a pH low enough to control microbial growth, typically below 4.2, but that same acidic range often sits close to the isoelectric point of common legume proteins, where solubility and emulsifying capacity are weakest. Formulators are effectively optimizing two competing constraints at once: food safety pushes pH down, protein functionality often wants it higher. This is one of the clearest reasons ingredient selection matters as much as formulation adjustment, a protein with a lower isoelectric point, or one that retains solubility across a wider pH window, gives more room to hit both targets without compromise.

Where Mung Bean Protein Fits Into This Picture

Given these recurring formulation challenges, it is worth considering why mung bean protein has attracted growing interest as an alternative plant protein for emulsion-based applications. Like any protein ingredient, its performance depends on both its intrinsic functional properties and the way it is processed within a formulation.

Mung bean protein isolate has demonstrated functional properties relevant to emulsified foods, including water-holding capacity, oil-holding capacity, emulsifying activity, and gelation behavior that are broadly comparable to those reported for soy protein isolate (Mudgil et al., 2017; Du et al., 2018). However, these properties should be interpreted within the context of the extraction method and ingredient specification, as protein functionality can vary considerably depending on processing conditions.

Like other legume proteins, mung bean protein exhibits pH-dependent solubility. Du et al. (2018) reported a characteristic U-shaped solubility profile, with minimum solubility near its isoelectric point (approximately pH 4.0–5.0) and substantially higher solubility at neutral pH. Since commercial mayonnaise is typically formulated around pH 3.5–4.2, mung bean protein is not exempt from the same acid-induced solubility challenges discussed earlier. Selecting the protein alone is therefore unlikely to solve emulsion stability; formulators should evaluate its solubility profile alongside the target pH, oil content, homogenization conditions, and hydrocolloid system.

Recent research also suggests that the way mung bean protein is processed can influence its emulsifying performance as much as the protein source itself. A review by Huang et al. (2024) summarized studies showing that different protein fractions exhibit different emulsifying properties, with certain fractionation methods producing sub-fractions that demonstrated higher emulsifying activity and stability than the unfractionated isolate or, under the experimental conditions evaluated, a soy protein isolate. These findings reinforce that extraction and fractionation methods can substantially influence ingredient functionality and that results should not be generalized across all commercial mung bean proteins.

Applied research on vegan mayonnaise supports this formulation-focused perspective. Aksoy Caf and Ersus (2025) developed vegan mayonnaise using mung bean protein isolate, both alone and after conjugation with citrus pectin through an ultrasound-assisted Maillard reaction. Under the conditions evaluated, the conjugated protein produced the smallest average oil droplet sizes (3.9–16.5 μm) and exhibited shear-thinning rheological behavior characteristic of commercial mayonnaise. The study illustrates how protein modification, rather than protein selection alone, can improve emulsion performance in acidified systems.

None of this suggests that mung bean protein is a universal replacement for pea or soy protein. Successful formulation still depends on factors including pH, oil phase volume, homogenization energy, order of ingredient addition, salt concentration, hydrocolloid selection, and storage conditions. Ingredient selection and process design work together; even a highly functional protein can produce an unstable emulsion if the processing conditions are not optimized.

A Note on OMN9 M80

OMN9 M80 is a mung bean protein isolate developed for emulsion applications. Given the functional profile above, amino acid completeness relative to pea, milder flavor relative to pea and soy, and demonstrated emulsifying performance in mayonnaise-style systems when properly formulated for the target pH, it may be worth evaluating in trials where pea or soy protein has been the limiting factor on flavor or interfacial stability. As with any legume protein, performance in a specific acidified system depends on how well the formulation accounts for its solubility curve, so formulators should run their own droplet-size and pH-solubility mapping before committing to a full-scale trial.

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