With the improvement of people’s living standard, consumers’ requirements for food are not only limited to reasonable nutritional value, but also require food to have satisfactory quality in appearance, color, aroma, taste, consistency, freshness and other sensory characteristics.

Emulsifiers, as tempering food additives, play an important role in the food industry. Let’s take a look at the mechanism of emulsifiers!

Emulsion

Commonly found in food emulsions, one phase is water or aqueous solution, collectively known as the hydrophilic phase; the other phase is immiscible with water in the organic phase, or lipophilic phase. Two immiscible liquids, such as water and oil phase can form two types of emulsion when mixed, that is, oil-in-water (O/W) and water-in-oil (W/O) emulsion.

In the oil-in-water emulsion oil to tiny drops dispersed in water, oil droplets for the dispersed phase, water for the dispersing medium, such as buttermilk that is an O/W type emulsion; in the water-in-oil emulsion is the opposite, water to tiny droplets dispersed in oil, water for the dispersed phase, oil for the dispersing medium, such as margarine that is a W / O type emulsion.

The mechanism of emulsifier

Food emulsifiers, also known as surfactants, or that is to make the immiscible liquid into a uniformly dispersed phase (emulsion) of the substance, added to the food can significantly reduce the interfacial tension between the oil and water phases, so that the immiscible oil (hydrophobic substances) and water (hydrophilic substances) to form a stable emulsion of the food additives.

Emulsifier on the one hand, through the two mutually exclusive phase surface, the formation of a thin molecular layer, reduce the surface free energy of the entire system, and the formation of new interfaces, emulsifier molecules with hydrophilic and lipophilic two types of groups, these two types of groups can be adsorbed in the oil and water respectively on the surface of the two mutually exclusive phases, the formation of a thin layer of molecules to reduce the interfacial tension of the two phases, that is, oil molecules with the lipophilic portion of emulsifier on one side, and the hydrophilic portion of water molecules with the other side of the emulsifier on the other side. In other words, the lipophilic part of oil molecules and emulsifier is on one side, and the hydrophilic part of water molecules and emulsifier is on the other side;

On the other hand, by forming a protective adsorption layer on the surface of the droplets, it gives the droplets a strong spatial stabilization effect. Generally, the more emulsifier is added, the greater the reduction of interfacial tension. In this way, the original immiscible substances can be evenly mixed to form a homogeneous state of the dispersion system, changing the original physical state, and then improve the internal structure of the food, improve the quality.

Hydrophilic-Lipophilic Equilibrium Value

Hydrophilic Lipophilic Balance (HLB)

Generally, emulsifiers with strong hydrophilicity become oil/water emulsions, and emulsifiers with strong lipophilicity become water/oil emulsions. In order to express the hydrophilic and lipophilic balance of an emulsifier, the HLB value (Hydrophilic Lipophilic Balance) is usually used and the hydrophilicity of an emulsifier is expressed in terms of the HLB value.There are various ways of calculating the HLB value.

Difference formula: HLB = hydrophilicity of hydrophilic group – hydrophobicity of lipophilic group

Ratio formula: HLB = hydrophilicity of hydrophilic group / hydrophobicity of lipophilic group

The HLB value of each emulsifier can be determined by experimental method, and it is stipulated that the HLB of the emulsifier with 100% lipophilicity is 0 (represented by paraffin wax), and the HLB of the emulsifier with 100% hydrophilicity is 20 (represented by potassium oleate), and it is divided into 20 equal parts, which indicates the strength of hydrophilicity and lipophilicity, and the bigger the value of HLB, the stronger the hydrophilicity, and the smaller the value of HLB, the stronger the lipophilicity.

The majority of edible emulsifiers are non-ionic surfactants with HLB values of 0-20, and the different HLB values of non-ionic emulsifiers and their related properties are shown in the table, while the HLB values of ionic surfactants range from 0-40. Therefore, all emulsifiers with an HLB value of <10 are mainly lipophilic, whereas emulsifiers with HLB values of ≥10 have a hydrophilic character.

For mixed emulsifiers, their HLB values are additive. Therefore, when two or more emulsifiers are mixed, the HLB value of the mixed emulsifier can be obtained by the mass fraction of each emulsifier in its composition:

HLBa,b =HLBa-A%+HLBb-B%

Where HLBa,b is the HLB value of emulsifier a, b after mixing; HLBa and HLBb are the HLB values of two emulsifiers a and b, respectively; A% and B% are the percentages of a and b in the mixed emulsifier, respectively (this formula applies only to non-ionic emulsifiers).

Preparation methods of emulsifiers and influencing factors

There are four preparation methods for emulsifiers, i.e., dry glue method, wet glue method, oil phase water phase mixing method, and mechanical method.

Dry glue method, that is, the water phase added to the oil phase containing emulsifier, the preparation of the first glue powder (emulsifier) and oil mixed well, add a certain amount of water, grinding emulsification into the colostrum, and then add water to dilute to the full amount.

Wet glue method, that is, the oil phase added to the water phase containing emulsifier, the preparation of the glue (emulsifier) first dissolved in water, made of slurry as the water phase, and then the oil phase added to the water phase in stages, grinding into colostrum, in the addition of water to the full amount.

The oil phase water phase mixed and added to the emulsifier, a certain amount of oil, water, mixed.

Gum arabic to the emulsifying bowl to be finely ground, and then add the oil-water mixture into it to be rapidly ground into colostrum, and then diluted with water.

Preparation of emulsifiers is mainly two liquids emulsified, and emulsification is good or bad on the quality of the emulsion has a great impact. Factors affecting emulsification are mainly interfacial tension, viscosity and temperature, emulsification time, the amount of emulsifier. Generally use the emulsifier that can significantly reduce the interfacial tension; the most suitable emulsification temperature of the emulsifier is about 70 ℃, if the nonionic surfactant is used as the emulsifier, the emulsification temperature should not exceed the blip point; generally, the more the dosage of the emulsifier, the more stable the emulsion is formed.