Preparation of emulsions depends on the scale at which it is produced.
- On a small scale, mortar and pestle can be used but their efficiency is limited. To overcome this drawback small electric mixers can be used although care must be exercised to avoid excessive entrapment of air.
- For large-scale production mechanical stirrers are used to provide controlled agitation and shearing stress to produce stable emulsions.
- The methods commonly used for preparation of emulsions can be divided into two categories:
(A) Trituration Method:
This method consists of the dry gum method and wet gum method.
(1) Dry Gum Method:
In this method, the oil is first triturated with gum with a little amount of water to form the primary emulsion. The trituration is continued till a characteristic ‘clicking’ sound is heard and thick white cream is formed. Once the primary emulsion is formed, the remaining quantity of water is slowly added to form the final emulsion.
(2) Wet Gum Method:
As the name implies, in this method first gum and water are triturated together to form a mucilage. The required quantity of oil is then added gradually in small proportions with thorough trituration to form the primary emulsion.
Once the primary emulsion has been formed remaining quantity of water is added to make the final emulsion.
(B) Bottle Method
This method is employed for preparing emulsions containing volatile and other non-viscous oils. Both dry gum and wet gum methods can be employed for the preparation.
As volatile oils have a low viscosity as compared to fixed oils, they require a comparatively large quantity of gum for emulsification.
In this method, oil or water is first shaken thoroughly and vigorously with the calculated amount of gum. Once this has emulsified completely, the second liquid (either oil or water) is then added all at once and the bottle is again shaken vigorously to form the primary emulsion. More water is added in small portions with constant agitation after each addition to produce the final volume.
Formulae for Primary Emulsion
Dry gum method or continental method
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