Food Emulsions

Food emulsions

Food emulsifiers belong to the class of surface-active chemicals (surfactants); specifically, they are surfactants with affinity for both water and fat. By lowering surface tension and making droplets smaller and more stable, emulsifiers create emulsions, and they are divided into ionic and non-ionic types. They have a water-loving (hydrophilic) head and a water-repelling (lipophilic) tail, which is why they can interact with both water and fat.

There are different kinds of emulsions, but the most common classification is oil-in-water (O/W) and water-in-oil (W/O). In oil-in-water emulsions, oil droplets are dispersed in water (the continuous phase), while in water-in-oil emulsions, water droplets are dispersed in oil (the continuous phase).

The most widely used food emulsifiers

An emulsion is a mixture of two or more immiscible liquids with two phases: a continuous (external) phase and a dispersed (internal) phase, with one liquid dispersed within the other.

In an oil-in-water emulsion, the external phase is water and the internal phase is oil. This type has a light texture, feels moist on contact and mixes easily with water. Emulsifiers create and stabilise such emulsions (for example mayonnaise). In products such as ice cream, they also help limit ice crystal formation and improve volume and uniformity.

In a water-in-oil emulsion, the external phase is oil and the internal phase is water; in other words, water droplets are dispersed in oil. These emulsions are usually thicker and heavier, do not mix with water and feel greasy.

The basic structure of an emulsifier has two parts: a fat-loving part that repels water (usually a long fatty acid chain) and a water-loving part (which may be charged or neutral). The fat-loving part sits in the oil phase and the water-loving part in the water phase, so small oil droplets stay dispersed. Emulsifiers are closely related to stabilisers, which maintain the emulsion state. Adding thickeners can also improve the consistency of foods; besides improving texture, these additives improve keeping quality and can extend shelf life.

Lecithin

Lecithin is one of the most widely used emulsifiers in cooking and baking. It is obtained from the fatty compounds found in egg yolk and other sources such as soy and sunflower. Its emulsifying ability comes from the phospholipids it contains, which prevent water and oil from separating. Lecithin keeps oil droplets dispersed in water and improves the stability and shelf life of food. It is a source of choline and phospholipids, but health claims for it at the levels used in food have not been proven.

Fatty acid derivatives

This group includes many emulsifiers derived from fatty acids, such as polyglycerol esters (PGE), polysorbates, stearoyl lactylates, propylene glycol esters and sucrose esters. PGE is used in desserts such as cakes and frozen desserts, and propylene glycol monostearate (PGMS) is used mainly in whipped toppings. Other products such as chewing gum, coffee products and sauces use sucrose esters to keep their particles dispersed.

Polyglycerol polyricinoleate (PGPR) is used in chocolate and confectionery. It reduces the viscosity and yield stress of molten chocolate so that it flows better and coats well with less cocoa butter. Added to foods, PGPR improves the flow of chocolate coatings and enhances the effect of lecithin, so manufacturers use it to maintain the quality of chocolate and other products that need a specific viscosity.

Ammonium phosphatide (E442)

This compound is made from vegetable oils such as rapeseed or sunflower and is used mainly in chocolate and confectionery. It helps achieve a uniform texture and stabilise the mixture, resulting in high-quality products, and it plays an important role in maintaining properties such as texture, aroma and consistency.

Mono- and diglycerides

Mono- and diglycerides are a varied group of compounds used in many industrial processes, especially in making foams. They help control fat aggregation by spreading fat evenly. In water-in-oil emulsions, monoglycerides help distribute the water droplets evenly in the oil. They improve structure and particle size, giving products a smooth, uniform texture. Other substances such as citric acid, propylene glycol and glycerin are used as processing aids alongside emulsifiers.

Factors affecting the stability of food emulsions

• Droplet size: finer droplets (from a homogeniser) give a more stable emulsion.
• Type and amount of emulsifier and its HLB value.
• Viscosity of the continuous phase: thickeners such as xanthan and guar slow droplet movement and separation.
• Temperature, pH and salt: sharp changes can break the emulsion.
• Freezing and thawing in products such as sauces.

Common examples of food emulsions

Conclusion

Food emulsions consist of two or more immiscible liquids, such as oil and water, with oil droplets dispersed in water or the reverse. Food emulsifiers, including natural emulsifiers, act as emulsifying agents or stabilisers and are used in many products such as confectionery, juices, chocolate, sauces and edible creams. They give foods uniformity, stability and smoothness and improve the eating experience. For more information, contact Mehr Gostar.

Frequently asked questions

What is a food emulsion?

A stable mixture of two immiscible liquids such as water and oil, made with the help of an emulsifier; examples are milk, mayonnaise, butter and ice cream.

What types of food emulsions are there?

Oil-in-water (O/W), such as milk and mayonnaise, and water-in-oil (W/O), such as butter and margarine.

What are the most widely used food emulsifiers?

Lecithin, mono- and diglycerides, polysorbates, sucrose esters, stearoyl lactylates and PGPR.

Why do food emulsions separate?

Because of large droplets, insufficient or unsuitable emulsifier, changes in temperature, pH or salt, and freezing and thawing.

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