Emulsions: mayonnaise and hollandaise

Mayonnaise and hollandaise are classic oil-in-water emulsions where dispersed oil droplets

are stabilised by emulsifiers—egg yolk lecithin in mayonnaise, and lecithin plus partially

denatured egg proteins and acid in hollandaise. Stabilisation occurs when amphiphilic

molecules orient at the oil‒water interface, reducing interfacial tension and allowing fine

droplets to be suspended within a continuous phase.

Temperature, shear rate, droplet size and emulsifier concentration control stability. In

mayonnaise, gradual oil incorporation under steady shear forms small droplets; too fast

addition causes phase inversion or breaking. Hollandaise is more fragile—heat denatures

yolk proteins to a point where they stabilise the emulsion, but excess heat causes

aggregation and separation. Acid increases protein solubility and stabilises both sauces,

while salt affects flavour and ionic interactions. Failure modes include broken sauces from

thermal shock, over-thinned mayonnaise from overbeating, or curdled hollandaise when

held too hot.

Takeaway: control temperature, emulsifier ratio and oil addition rate to produce glossy,

stable emulsions and recover broken sauces using measured corrective actions.

Kitchen action. For mayonnaise, add oil very slowly at the start and use a whisk or

controlled-speed blender for consistent droplet formation. For hollandaise, cook over

gentle indirect heat and keep at a warm—not hot—holding temperature; if separation

occurs, rescue with a small amount of warm water or a fresh yolk.

Lecithin is a surface-active phospholipid frequently used to stabilise culinary foams by

lowering surface tension and forming a flexible interfacial film. At an air‒water boundary

lecithin orients its hydrophobic tails toward air and polar headgroups toward water,

creating a viscoelastic layer that slows bubble coalescence. It also cooperates with proteins:

lecithin can adsorb more rapidly than many proteins, then transfer stabilising roles to

slower-forming protein films, improving initial foaming and long-term stability. Practical

variables include source (soy, sunflower), concentration, temperature, and the presence of

fats or sugars; excess oil will disrupt films and overdozing lecithin can cause collapse by

making the film too fluid. Mechanical overwhipping oxidises and ruptures films, while high

heat reduces interfacial strength. In complex preparations, pH and salt change adsorption

dynamics and should be considered. For professional kitchens the priority is controlled

addition and testing: pilot small batches, adjust emulsifier dosage and whipping regimen,

and always account for other ingredients that interfere with surface activity. A measured

approach gives reliable, long-lasting culinary foams.

Kitchen action. Run a bench trial when introducing lecithin: start with a small,

reproducible quantity and vary only one parameter at a time (temperature, whipping

speed, lecithin dose). Record results and standardise the process sheet for the brigade,

noting sources of lecithin and any oil-containing ingredients that require compensation.

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