Under certain conditions, two immiscible liquids, one with particles (droplets or liquid crystals) dispersed in the other in the formation of the system called emulsion. Emulsions are widely used in industrial and agricultural production, daily life and physiological phenomena. Emulsion is thermodynamically unstable system, in order to carry out emulsification and get a certain stability of the emulsion, to add a third substance that can reduce the interfacial energy ‘this substance is called emulsifier.

The emulsifier is the key to the stability of the emulsion, mostly various types of surfactants. However, not all surfactants are suitable as emulsifiers, so how to choose emulsifiers in the preparation of emulsions becomes a key issue.

According to the different properties of oil dispersed in water or water dispersed in oil, emulsifiers are roughly divided into water-in-oil (W/O) type and oil-in-water (O/W) type, and the stability of emulsification is mainly determined by the balance of hydrophilic and lipophilic groups in the molecules of emulsifiers. This balance is usually expressed as HLB value. This value is usually 1~20, the closer to 1 the more lipophilic, the closer to 20 the more hydrophilic.

The role of food emulsifiers are mainly divided into three aspects: ① reduce oil – water interfacial tension, promote emulsification, in the oil – water – emulsifier interface to form a phase equilibrium, stabilization of emulsifiers; ② interaction with starch and protein and other components to improve the structure and rheological properties of the food; ③ improve the crystallization of the fat oil.

Summary of HLB value of commonly used emulsifiers

Trade name

Chinese Name

Type

HLB

—

Oleic acid

Anion

1

Span 85

Sorbitan trioleate, anhydrous

Nonionic

1.8

Arlacel 85

Sorbitan trioleate

Nonionic

1.8

Atlas G-1706

Polyoxyethylene sorbitol beeswax derivative

Nonionic

2

Span 65

Sorbitan tristearate, anhydrous

Nonionic

2.1

Arlacel 65

Sorbitan tristearate

Nonionic

2.1

Atlas G-1050

Polyoxyethylene sorbitan hexastearate

Nonionic

2.6

Emcol EO-50

Ethylene Glycol Fatty Acid Ester

Nonionic

2.7

Emcol ES-50

Ethylene glycol fatty acid ester

Nonionic

2.7

Atlas G-1704

Polyoxyethylene sorbitol beeswax derivative

Nonionic

3

Emcol PO-50

Propylene glycol fatty acid ester

Nonionic

3.4

Atlas G-922

Propylene glycol monostearate

Nonionic

3.4

“Pure”

Propylene Glycol Monostearate

Nonionic

3.4

Atlas G-2158

Propylene Glycol Monostearate

Nonionic

3.4

Emcol PS-50

Propylene Glycol Fatty Acid Ester

Nonionic

3.4

Emcol EL-50

Ethylene glycol fatty acid ester

Nonionic

3.6

Emcol PP-50

Propylene glycol fatty acid ester

Nonionic

3.7

Arlacel C

Sorbitan sesquioleate, anhydrous

Nonionic

3.7

Arlacel 83

Sorbitan sesquioleate, anhydrous

Nonionic

3.7

AtlasG-2859

Polyoxyethylene sorbitan 4.5 oleate

Nonionic

3.7

Atmul 67

Glycerol monostearate

Nonionic

3.8

Atmul 84

Glycerol monostearate

Nonionic

3.8

Tegin 515

Glycerol monostearate

Nonionic

3.8

Aldo 33

Glycerol monostearate

Nonionic

3.8

“Pure”

Glycerol monostearate

Nonionic

3.8

Ohlan

Hydroxylated lanolin

Nonionic

4

AriasG-1727

Polyoxyethylene sorbitol beeswax derivative

Nonionic

4

Emcol PM-50

Propylene glycol fatty acid ester

Nonionic

4.1

Span 80

Sorbitan monooleate

Nonionic

4.3

Arlacel 80

Sorbitan monooleate

Nonionic

4.3

Atlas G-917

Propylene glycol monolaurate

Nonionic

4.5

AtlasG-385l

Propylene glycol monolaurate

Nonionic

4.5

EmcolPL-50

Propylene Glycol Fatty Acid Ester

Nonionic

4.5

Span 60

Sorbitan monostearate

Nonionic

4.7

Arlacel 60

Sorbitan monostearate

Nonionic

4.7

AtlasG-2139

Diethylene glycol monooleate

Nonionic

4.7

Emcol DO-50

Diethylene glycol fatty acid ester

Nonionic

4.7

AtlasG-2146

Diethylene glycol monostearate

Nonionic

4.7

Emcol DS-50

Diethylene glycol fatty acid ester

Nonionic

4.7

Ameroxol OE-2

Polyoxyethylene (2EO) oleyl ether

Nonionic

5

AtlasG-1702

Polyoxyethylene sorbitol beeswax derivative

Nonionic

5

Emcol DP-50

Diethylene glycol fatty acid ester

Nonionic

5.1

Aldo 28

Glycerol monostearate

Nonionic

5.5

Tegin

Glycerol monostearate

Nonionic

5.5

Emcol DM-50

Diethylene glycol fatty acid ester

Nonionic

5.6

Glucate-SS

Methyl glucoside sesquistearate casein

Nonionic

6

AtlasG-1725

Polyoxyethylene sorbitol beeswax derivative

Nonionic

6

AtlasG-2124

Diethylene glycol monolaurate

Nonionic

6.1

Emcol DL-50

Diethylene glycol fatty acid ester

Nonionic

6.1

Glaurin

Diethylene glycol monolaurate

Nonionic

6.5

Span 40

Sorbitan monopalmitate

Nonionic

6.7

Arlacel 40

Sorbitan monopalmitate

Nonionic

6.7

AtlasG-2242

Polyoxyethylene dioleate

Nonionic

7.5

AtlasG-2147

Tetraethylene glycol monostearate

Nonionic

7.7

AtlasG-2140

Tetraethylene glycol monooleate

Nonionic

7.7

AtlasG-2800

Polyoxypropylene mannitol dioleate

Nonionic

8

Atlas G-1493

Polyoxyethylene sorbitan lanolin oleic acid derivative

Nonionic

8

Atlas G-1425

Polyoxyethylene sorbitol lanolin derivative

Nonionic

8

Atlas G-3608

Polyoxypropylene stearate

Nonionic

8

Solulan 5

Polyoxyethylene (5EO) lanolin ether

Nonionic

8

Span 20

Sorbitan Laurate

Nonionic

8.6

Arlacel 20

Sorbitan Laurate

Nonionic

8.6

Emulphor VN-430

Polyoxyethylene fatty acid

Nonionic

8.6

Atbs G-2111

Polyoxyethylene oxypropylene oleate

Nonionic

9

Atlas G-1734

Polyoxyethylene sorbitol beeswax derivative

Nonionic

9

Atlas G-2125

Tetraethylene glycol monolaurate

Nonionic

9.4

Brij 30

Polyoxyethylene Lauryl Ether

Nonionic

9.5

Tween 61

Polyoxyethylene (4EO) sorbitan monostearate anhydrous

Nonionic

9.6

Atlas G-2154

Hexaethylene Glycol Monostearate

Nonionic

9.6

Splulan PB-5

Polyoxypropylene (5PO) lanolin ether

Nonionic

10

Tween 81

Polyoxyethylene(5EO) sorbitan monooleate

Nonionic

10

Atlas G-1218

Polyoxyethylene esters of mixed fatty acids and resin acids

Nonionic

10.2

Atlas G-3806

Polyoxyethylene cetyl ether

Nonionic

10.3

Tween 65

Polyoxyethylene (20EO) sorbitan tristearate anhydrous

Nonionic

10.5

Atlas G-3705

Polyoxyethylene Lauryl Ether

Nonionic

10.8

Tween 85

Polyoxyethylene (20EO) Sorbitan Trioleate Anhydrous

Nonionic

11

Atlas G-2116

Polyoxyethylene Oxypropylene Oleate

Nonionic

11

Atlas G-1790

Polyoxyethylene lanolin derivative

Nonionic

11

Atlas G-2142

Polyoxyethylene monooleate

Nonionic

11.1

Myrj 45

Polyoxyethylene monostearate

nonionic

11.1

Atlas G-2141

Polyoxyethylene monooleate

Nonionic

11.4

P.E.G.400 monooleate

Polyoxyethylene monooleate

Nonionic

11.4

Atlas G-2076

Polyoxyethylene monopalmitate

Nonionic

11.6

S-541

Polyoxyethylene monostearate

Nonionic

11.6

P.E.G.400 monostearate

Polyoxyethylene monostearate

Nonionic

11.6

Atlas G-3300

Alkaryl sulfonate

Anionic

11.7

–

Triethanolamine oleate

anionic

12

Ameroxl OE-10

Polyoxyethylene (10EO) oleyl ether

Nonionic

12

Atlas G-2127

Polyoxyethylene monolaurate

Nonionic

12.8

Igepal CA-630

Polyoxyethylene alkyl phenol

Nonionic

12.8

Solulan 98

Polyoxyethylene (10EO) acetylated lanolin derivative

Nonionic

13

Atlas G-1431

Polyoxyethylene sorbitol lanolin derivative

Nonionic

13

Atlas G-1690

Polyoxyethylene alkyl aryl ether

Nonionic

13

S-307

Polyoxyethylene monolaurate

Nonionic

13.1

P.E.G 400 monolurate

Polyoxyethylene monolaurate

Non-ionic

13.1

Atlas G-2133

Polyoxyethylene Lauryl Ether

Nonionic

13.1

Atlas G-1794

Polyoxyethylene castor oil

Nonionic

13.3

Emulphor EL-719

Polyoxyethylene Vegetable Oil

Nonionic

13.3

Tween 21

Polyoxyethylene (4EO) Sorbitan Monolaurate Anhydrous

Nonionic

13.3

Renex 20

Polyoxyethylene ester with fatty acids and resin acids

Nonionic

13.5

Atlas G-1441

Polyoxyethylene sorbitol lanolin derivative

Nonionic

14

Solulan C-24

Polyoxyethylene (24EO) cholesteryl ether

Nonionic

14 Solulan PB-20

Solulan PB-20

Polyoxypropylene(20PO) lanolin ether

Nonionic

14

NP10

TX10

Non-ionic

14.5

Atlas G-7596j

Polyoxyethylene sorbitan monolaurate anhydrous

Nonionic

14.9

Tween 60

Polyoxyethylene (20EO) sorbitan monostearate anhydrous

Nonionic

14.9

Ameroxol OE-20

Polyoxyethylene (20EO) oleyl ether

Nonionic

15

Glucamate SSE-20

Polyoxyethylene(20EO)methyl glucoside sesquioleate

Nonionic

15 Glucamate

Solulan 16

Polyoxyethylene(16EO) lanolin ether

Nonionic

15

Solulan 25

Polyoxyethylene(25EO) lanolin ether

Nonionic

15

Solulan 97

Polyoxyethylene (9EO) acetylated lanolin derivative

Nonionic

15

Tween 80

Polyoxyethylene (20EO) Sorbitan Monooleate Anhydrous

Nonionic

15

Myrj 49

Polyoxyethylene monostearate

Nonionic

15

Altlas G-2144

Polyoxyethylene monooleate

Nonionic

15.1

Atlas G-3915

Polyoxyethylene oleyl ether

Nonionic

15.3

Atlas G-3720

Polyoxyethylene octadecanol

Nonionic

15.3

Atlas G-3920

Polyoxyethylene oleyl alcohol

Nonionic

15.4

Emulphor ON-870

Polyoxyethylene fatty alcohol

Nonionic

15.4

Atlas G-2079

Polyethylene Glycol Monopalmitate

Nonionic

15.5

Tween 40

Polyethylene Oxide (20EO) Sorbitan Monopalmitate Anhydrous

Nonionic

15.6

Atlas G-3820

Polyoxyethylene Cetyl Alcohol

Nonionic

15.7

Atlas G-2162

Polyoxyethylene oxypropylene stearate

Nonionic

15.7

Atlas G-1741

Polyoxyethylene sorbitol lanolin derivative

Nonionic

16

Myrj 51

Polyoxyethylene monostearate

Nonionic

16

Atlas G-7596P

Polyoxyethylene anhydrous sorbitan monolaurate

Nonionic

16.3

Atlas G-2129

Polyoxyethylene monolaurate

Nonionic

16.3

Atlas G-3930

Polyoxyethylene oleyl ether

Nonionic

16.6

Tween 20

Polyoxyethylene (20EO) Sorbitan Monolaurate Anhydrous

Nonionic

16.7

Brij 35

Polyoxyethylene Lauryl Ether

Nonionic

16.9

Myrj 52

Polyoxyethylene monostearate

Nonionic

16.9

Myrj 53

Polyoxyethylene monostearate

Nonionic

17.9

-Sodium oleate

Sodium oleate

Anionic

18

Atlas G-2159

Polyoxyethylene Monostearate

Nonionic

18.8

-Potassium Oleate

Potassium oleate

Anionic

20

Atlas G-263

Sodium N-hexadecyl-N-ethylmorpholinoethyl sulfate

Cationic

25-30

Texapon K-12

Pure sodium lauryl sulfate

Anionic

40

HLB value and selection of the optimal emulsifier[1]

Each emulsifier has a specific HLB value, and it is often difficult for a single emulsifier to meet the emulsification requirements of a multi-component system. Usually, a variety of emulsifiers with different HLB values are mixed together to form a hybrid emulsifier, which can not only meet the requirements of complex systems, but also greatly improve the emulsification effect. To emulsify an oil-water system, the following steps can be taken to select the best emulsifier.

I. Determination of optimal HLB value for oil-water system

Select a pair of emulsifiers with large differences in HLB values, for example, Span-60 (HLB = 4.3) and Tween-80 (HLB = 15), formulated into a series of mixed emulsifiers with different HLB values in different proportions, and then use this series of mixed emulsifiers to make a series of emulsions from a specified oil-water system. The emulsification efficiency of each emulsion (can be represented by the stability time of the emulsion, can also be represented by other stable properties), and the calculated HLB of the mixed emulsifier, graph, a bell-shaped curve, and the curve with the highest peak of the corresponding HLB value that is emulsifying the specified system of the required HLB value.

Obviously, the most suitable HLB value can be obtained by using a mixed emulsifier, but this emulsifier may not be the best efficiency. The efficiency of an emulsifier means that the concentration of emulsifier required to stabilize the specified emulsion is the lowest and cheapest. The emulsifier that is expensive but requires much lower concentration may also be more efficient than the emulsifier that is cheaper and more concentrated.

II. Determination of emulsifier

On the premise of maintaining the required HLB value of the selected emulsification system, several pairs of emulsifiers are selected and mixed so that the HLB value of each mixed emulsifier is the value determined by the above method. The specified system is emulsified with these emulsifiers, the stability is measured, and the emulsification efficiency is compared until the most efficient pair of emulsifiers is found.

It is worth noting that the concentration of the emulsifiers is not mentioned here, but this does not affect this method of selection, since the HLB value required for the preparation of a stable emulsion has little to do with the concentration of the emulsifiers. It is in the region of emulsion instability, when the emulsifier concentration is very low or the concentration of the internal phase is too high, that this method is affected [2].

When selecting an emulsifier using the HLB method, not only the optimum HLB value should be considered, but also the affinity of the emulsifier to the dispersed phase and the dispersing medium should be taken into account. An ideal emulsifier should not only have a strong affinity with the oil phase, but also have a strong affinity with the aqueous phase.

By mixing an emulsifier with a small HLB value with an emulsifier with a large HLB value, a mixed film is formed with a strong affinity for both the oil phase and the water phase, which can take care of both requirements at the same time. Therefore, the use of mixed emulsifiers is more effective than the use of a single emulsifier.

To summarize, the method of deciding the emulsifier formula required for emulsification of a specified system is to choose a pair of emulsifiers arbitrarily, change the mixing ratio within a certain range, and then change the types and ratios of the compound emulsifiers to get the highest HLB value, but still need to maintain the required HLB value, until the highest efficiency of the compound emulsifier is found.

In the preparation of stabilized emulsions, the selection of the most suitable emulsifier to achieve the best emulsification effect is the key issue. There is no perfect theory for the selection of emulsifiers.

The HLB value of surfactants has great value in selecting emulsifiers and determining the dosage of compound emulsifiers, and its advantage is mainly reflected in its additivity, which can be calculated simply; the problem is that other factors are not taken into account on the HLB value, especially the influence of temperature, which is especially prominent in the nonionic emulsifiers with great dosage in recent years.

In addition, the HLB value can only roughly predict the type of emulsion to be formed, and cannot give the concentration of emulsifier at the time of optimal emulsification, nor can it predict the stability of the resulting emulsion. Therefore, applying the HLB value to select emulsifiers is a more effective method, but it also has certain limitations and needs to be referred to in combination with other methods in practical applications.