Everything Worth Understanding About Fats And Emulsions

What Are Fats, Really?

Fats are triglycerides—molecules made of glycerol linked to three fatty acid chains. These chains can be saturated (straight, packed tight) or unsaturated (bent, more fluid). This structure explains why butter is solid at room temperature (high saturated fat) and olive oil is liquid (high unsaturated fat).

Fats are hydrophobic—they repel water. That’s a central fact for emulsions.

The Two Personalities of Fat: Hydrophobic and Lipophilic

Fat molecules are nonpolar, meaning they don’t mix with polar water. But they love other fats—that’s lipophilicity. In cooking, this dual nature becomes key: we can use emulsifiers, which have both a water-loving (hydrophilic) end and a fat-loving (lipophilic) end, to bridge the gap.

What Is an Emulsion?

An emulsion is a stable mixture of two immiscible liquids, like oil and water. One liquid is dispersed as tiny droplets in the other. Two types: oil-in-water (mayonnaise, milk) where oil droplets are in water, and water-in-oil (butter, margarine) where water droplets are in oil.

Without an emulsifier, the droplets quickly merge—coalescence—and the liquids separate.

The Heroes: Emulsifiers

These molecules position themselves at the oil-water interface, stabilizing the droplets.

How to Build a Stable Emulsion

Start with a base of water and emulsifier. Slowly drizzle oil while whisking vigorously. This breaks oil into smaller droplets, increasing surface area. Adding oil too quickly causes the emulsion to break—the droplets coalesce.

• Use room-temperature eggs for mayonnaise
• Add acid (vinegar
• lemon) first to help dissolve egg proteins
• Drizzle oil slowly
• especially at the beginning
• Whisk constantly to maintain droplet dispersion

Common Mistakes and How to Fix Them

If an emulsion breaks, it’s usually because of temperature shock or adding oil too fast. To fix: start a new base of water + emulsifier, then slowly whisk in the broken emulsion as if it were oil.

• Overheating: butter sauces can split if too hot
• remove from heat and whisk in cold water
• Too much oil: dilute with a little water or vinegar and re-emulsify
• Lack of emulsifier: add more egg yolk or a pinch of mustard

Frequently Asked Questions