6 Emulsifiers for the food industry
Dhinal Patel
11.1 Introduction
Emulsifiers are additives that allow normally immiscible liquids, such as oil and water, to form a stable mixture.
An emulsion is a blend of two immiscible liquids, with droplets of one phase (dispersed phase) distributed in the other phase (continuous phase). In general these are unstable systems in which the dispersed phase droplets tend to agglomerate or coalescence and separate out. The boundary between the two phases is called the interface.
Emulsifiers contain both hydrophilic and lipophilic parts. The hydrophilic head is easy to hydrate (water soluble) and the lipophilic tail is impossible or very difficult to hydrate (oil soluble). Emulsifiers concentrate at the interface between oil and water and reduce the surface or interfacial tension, thereby making the emulsion more stable (Figure: 11.1). In many industries emulsifiers are referred to as “surfactants”, which is an abbreviation of surface active agents.
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Figure: 11.1 Working of Emulsifier
In commercial food emulsifiers the hydrophilic part can consist of glycerol, sorbitol, sucrose, propylene glycol or polyglycerol. The lipophilic part is formed by fatty acids derived from fats and oils such as soybean oil, rapeseed oil, coconut oil and palm kernel oils.
The stability of an emulsion depends on:
- Droplet size: a smaller droplet size facilitates emulsion stability. The droplet size can be influenced by homogenization.
- Viscosity of continuous phase: a higher viscosity facilitates emulsion stability. The viscosity of the water phase can be influenced by the addition of hydrocolloids or thickening agents.
- Specific density of the two phases: if the difference in density between the two phases is small, the emulsion will be more stable. For essential oils in beverages weighting agents can be used to increase the density of the essential oil.
- Quality of the interfacial film: the film can consist of emulsifiers and / or proteins.
11.2 HLB: Hydrophilic Lipophilic Balance Concept
Emulsifiers can be characterized by the Hydrophilic Lipophilic Balance. The balance is measured on molecular weight and is an indication of the solubility of the emulsifier. The HLB scale varies between 0 and 20.
An emulsifier with a low HLB value is more soluble in oil and promotes water-in-oil emulsions. An emulsifier with a high HLB value is more soluble in water and promotes oil-in-water emulsions.
The HLB value is a somewhat theoretical value, it only considers water and oil, and food systems are more complicated. But the HLB value of an emulsifier can be used as an indication about its possible use.
11.3 Emulsifiers used in the food processing industry
Following emulsifiers are generally used in the food processing industry
11.4 Functions of emulsifiers:
- Formation of emulsion: Reduction of surface as interfacial tension at the surface or interface, which promotes mixing of two immiscible liquids. (Emulsification)
- Stabilization of emulsion: Formation of phase equilibrium between water-emulsifier-oil at the interface which stabilizes the emulsion.
- Modification of textural and rheological properties of foods: By interaction with starch and protein components in foods.
- Modification of the crystallization of fats and oils.
- Other: aeration, agglomeration, antisplattering, coating, creaming, crumb softening, dough strengthening, extrusion aid, fat distribution , fat sparing, foam stabilizing, foam stiffing, increase hat stability, moisture retention, plasticity, decrease stickiness, release, viscosity increase or decrease.
In addition to their major function of producing and stabilizing emulsions, food emulsifiers (or surfactants) contribute to numerous other functional roles. Table 11.1 is a list of functional properties of food emulsifiers compiled from a variety of sources.
Table 11.1 Functional Properties of Food Emulsifiers
| Functions | Product examples |
| Emulsification, water-in-oil emulsions | Margarine |
| Emulsification, oil-in-water emulsions | Mayonaise |
| Aeration | Whipped toppings |
| Whippability | Whipped toppings |
| Inhibition of fat crystallization | Candy |
| Softening | Candy |
| Antistaling | Bread |
| Dough conditioner | Bread dough |
| Improve loaf volume | Bread |
| Reduce shortening requirements | Bread |
| Pan-release agent | Yeast-leavened and other dough and batter products |
| Fat stabilizer | Food oils |
| Antispattering agent | Margarine and frying oils |
| Antisticking agent | Caramel candy |
| Protective coating | Fresh fruits and vegetables |
| Surfactant | Molasses |
| Control viscosity | Molten chocolate |
| Improved solubility | Instant drinks |
| Starch complexation | Instant potatoes |
| Humectant | Cake icings |
| Plasticizer | Cake icings |
| Defoaming agent | Sugar production |
| Stabilization of flavor oils | Flavour emulsions |
| Promotion of ‘‘dryness’’ | Ice cream |
| Freeze–thaw stability | Whipped toppings |
| Improve wetting ability | Instant soups |
| Inhibition of sugar crystallization | Panned coatings |
11.5 Emulsifier Selection Criteria
Several parameters should be considered during emulsifier selection. These parameters include
- Approval of the emulsifier by the appropriate government agency
- Desired functional properties
- End product application
- Processing parameters
- Synergistic effect of other ingredients
- Cost
11.6 Desirable Characteristics of Food Emulsifiers
- Ability to reduce surface or interfacial tension.
- Ability to be readily absorbed at the interface.
- Possessing the proper balance at hydrophilic and lipophilic parts (groups), so that desirable type of emulsion (O/W or W/O) can be stabilized.
- Ability to impact a large electro kinetic potential to dispersed phase (droplets)
- Ability to function effectively at low concentration.
- Resistance to chemical changes.
- Lack of odour, colour, etc.
- Safe non toxic.
11.7 Application of Emulsifier
It should be noted that in many food applications combination of emulsifiers are used to achieve the optimal performance.
11.6.1 Bakery
11.8 Conclusion
Food emulsifiers have versatile application in food industry. Food emulsifiers exert several technical effects and can be useful tools to address new product trends. Some trends that may impact on demands for new and modified emulsifier compositions and applications.
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Web links
- http://www.rikenvitamin.com/foodingredients/emulsifier/app_function.html
- http://www.rikenvitamin.com/foodingredients/emulsifier/kind.html