FOOD CHEMISTRY: FOOD ADDITIVES
Diagram
Joining oil and water, and holding the mix together
Emulsifier
Joins oil and water. It sits at the oil and water boundary and stops the drops from joining back together.
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Stabilizer
Holds texture over time. It thickens the water phase, binds water, and stops separation, ice crystals and settling.
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Use in ice cream
Both are used together in ice cream, but for different jobs, as Marshall, Goff and Hartel describe.
Figure 1: Emulsifiers join oil and water; stabilizers hold the texture over time. Drawn in our own style from Marshall, Goff and Hartel, Ice Cream, 6th ed., chapter on ice cream ingredients.
Introduction
Emulsifiers and stabilizers are both additives that keep a food mixture together, but they do different jobs. An emulsifier joins oil and water: it sits at the boundary between oil drops and water and stops the drops from joining back together. A stabilizer holds texture over time: it thickens the water phase, binds water, and stops separation, ice crystal growth and settling during storage. A food can need one, the other, or both.
Marshall, Goff and Hartel cover stabilizers and emulsifiers together in the ingredients chapter of Ice Cream, and that book is the source for this article.
Quick comparison
Table 1: Emulsifier compared with stabilizer
| Aspect | Emulsifier | Stabilizer |
|---|---|---|
| Job | Joins oil and water into an emulsion | Holds texture and stops change over time |
| Where it acts | At the boundary between oil drops and water | Through the whole water phase |
| What it stops | Oil drops joining back together and separating out | Separation, settling, and ice crystal growth in storage |
| Chemical type | Often a small molecule with a water loving end and a fat loving end, such as lecithin or mono and diglycerides | Often a large polysaccharide or protein, such as guar gum, locust bean gum or carrageenan |
| Effect on texture | Makes the mix smooth and helps air to be whipped in | Makes the mix thicker and gives body |
| Effect in ice cream | Promotes fat destabilisation, which helps the structure and the melting behaviour | Controls ice crystal growth and gives a smooth, slow melting texture |
| When it works | During mixing and whipping, when the emulsion is made | During storage, when the food must stay unchanged |
| Amount | Used in small amounts | Used in small amounts |
| Examples | Lecithin, mono and diglycerides, egg yolk | Guar gum, locust bean gum, carrageenan, cellulose gum |
| If it is left out | Oil and water separate | Texture spoils in storage: ice crystals grow, serum separates, body is lost |
Scientific explanation
Definition
An emulsifier is a substance that helps oil and water mix and stay mixed, by sitting at the boundary between oil drops and water and lowering the tension there, so the drops stay small and do not join back together. A stabilizer is a substance that holds the texture of a food over time, by thickening the water phase and binding water, so separation, settling and ice crystal growth are slowed. In ice cream the two are used together, but for these different jobs.
Working principle
An emulsifier has one end that likes water and one end that likes fat, so it sits at the oil and water boundary with each end in the phase it likes. That coat around each oil drop stops the drops from merging. A stabilizer dissolves in the water phase and makes it thick, so drops, air cells and ice crystals move slowly and cannot grow or settle quickly. In ice cream, the emulsifier helps the fat to partly join into a network that holds air, while the stabilizer binds water so ice crystals stay small and the product melts slowly and smoothly.
Apparatus
The books used here name no laboratory apparatus for telling the two apart, so no apparatus list is given.
Measurement procedure
The books used here name no single standard laboratory procedure for telling the two apart. The distinction is made from the definitions and properties given above, not from one test.
Factors affecting readings
Temperature, mixing speed and the order of adding ingredients change how well an emulsifier works. Concentration, pH and the presence of salts change how thick a stabilizer makes the mix. The fat content of the food changes which emulsifier is needed, and storage temperature changes how fast a stabilizer is needed to act.
Formulas and calculations
The books used here give no formula for this comparison, so no formula or worked calculation is given.
Industrial applications
- Emulsifiers are used in mayonnaise, salad dressings and sauces to keep oil and water mixed.
- Stabilizers are used in ice cream to control ice crystals and to give body, as Marshall, Goff and Hartel describe.
- Emulsifiers are used in chocolate and margarine to keep the fat phase smooth.
- Stabilizers are used in yoghurt and sauces to stop serum separation and to thicken.
- Both are used together in ice cream, frozen desserts and whipped toppings.
Advantages and limitations
- Emulsifier: advantage: makes oil and water stay mixed and helps air to be whipped in. Limitation: it cannot stop ice crystals growing or texture changing in storage.
- Stabilizer: advantage: holds texture over storage and gives a smooth, slow melting product. Limitation: too much gives a gummy or slimy texture, and it cannot make oil and water mix in the first place.
- Emulsifier: advantage: used in very small amounts for a large effect. Limitation: the wrong emulsifier for the fat can fail to hold the emulsion.
FAQ
Can a stabilizer replace an emulsifier?
No. A stabilizer thickens the water phase, but it does not sit at the oil and water boundary, so oil and water still separate.
Why does ice cream need both?
The emulsifier builds the fat network that holds air, and the stabilizer binds water so ice crystals stay small in storage.
What is lecithin?
Lecithin is an emulsifier, found in egg yolk and soya, with a water loving end and a fat loving end.
What is guar gum?
Guar gum is a stabilizer, a polysaccharide that thickens the water phase and binds water.
