Question 1

What is emulsification, and why does mayonnaise split?

Accepted Answer

An **emulsion** is a stable mixture of two liquids that do not normally mix — oil and water — and it splits when the structure holding them together breaks down.

**Why oil and water separate.** Water molecules are **polar** and attract each other strongly. Oil is non-polar. Left alone, water molecules pull together and push oil out, which is why a dressing separates within seconds.

**What an emulsion actually is.** One liquid broken into **tiny droplets suspended** in the other. Mayonnaise is oil droplets dispersed in a small amount of water-based liquid — despite being mostly oil by volume, which surprises people.

**The role of the emulsifier.** A molecule with a water-loving end and an oil-loving end, which sits at the boundary of each droplet and stops droplets merging. In mayonnaise that is **lecithin** from egg yolk. Mustard also contributes, and is added in many recipes as much for this as for flavour.

**Why mechanical work matters.** Whisking breaks the oil into smaller droplets. Smaller droplets mean more surface area, more emulsifier at the interface, and a thicker, more stable result — which is why mayonnaise thickens as you beat it.

**Why it splits:**

**Oil added too fast.** The commonest cause. There must be enough emulsifier and enough agitation to coat each new droplet. Too much oil at once overwhelms the system, droplets merge, and it breaks.

**Too much oil for the amount of yolk.** There is a ceiling.

**Cold ingredients**, which make oil more viscous and harder to disperse.

**Heat**, which destabilises the emulsion and can curdle egg-based sauces.

**How to rescue a split mayonnaise.** Start again in a clean bowl with a fresh yolk, or a teaspoon of mustard or water, and **whisk the broken mixture into it very slowly** as though it were oil. This works reliably and is worth knowing.

**Other emulsions in cooking:** hollandaise and béarnaise, which also rely on yolk and split with heat; vinaigrette, a **temporary** emulsion that separates because it has little emulsifier; butter, a water-in-fat emulsion; and cream sauces, where starch and dairy proteins stabilise the mixture.

Question 2

Why do egg whites whip, and what stops them?

Accepted Answer

Because whisking unfolds the proteins in the white, and those unfolded proteins arrange themselves around air bubbles and hold them there. Anything that interferes with that arrangement stops it

Question 3

Why does over-whipped cream turn into butter?

Accepted Answer

Because whipping and churning are the same process taken to different points — and cream that has gone too far has not been ruined so much as converted into something else. What cream is. An emulsion

Question 4

What is a roux, and why do sauces split?

Accepted Answer

A roux is flour cooked in fat, used to thicken sauces. Understanding how it works explains most sauce failures. How it thickens. Flour contains starch granules. Heated in liquid, they absorb water

Question 5

Why do recipes say to fry spices before adding liquid?

Accepted Answer

Because the compounds that carry most spice flavour are fat-soluble, and heating spices in fat extracts and disperses them in a way water cannot. The technique is called blooming, and it is the

Question 6

How is cheese actually made?

Accepted Answer

By separating milk into curds and whey, then controlling what happens to the curd — and almost every difference between cheeses comes from decisions made in the hours and months after that

Question 7

Why do recipes say to use eggs at room temperature?

Accepted Answer

Because temperature affects how eggs emulsify and incorporate air, and in baking those two properties determine texture more than almost anything else. The main reasons: Emulsification. Cake batters

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