• Emulsifier

Emulsifiers are food additives which combine ingredients that would otherwise separate, ensuring stability and texture in a wide range of foods. They achieve this by positioning themselves at the interfacial layers where the 2 substances meet. Each emulsifier molecule has 2 ends, including the hydrophilic end which is attracted towards the water phase and hydrophobic end which is attracted towards the oil phase. 

This allows emulsifiers to stabilise mixtures, preventing them from separating. They are naturally present in egg yolks and dairy products and are commonly added to packaged, frozen and processed food to prevent oil separation and to prolong shelf life.

Examples of emulsifiers include monoglycerides and diglycerides, with its use dating back to 1930s. Monoglycerides and diglycerides consist of a glycerol molecule bonded to 1 or 2 fatty acid(s), in which the hydroxyl group(s) is the hydrophilic end attracted to polar water molecules whereas the the fatty acid(s) is the hydrophobic end attracted to non-polar oil molecules. Monoglycerides and diglycerides are produced through a process called interesterification or glycerolosis, which involves rearranging the fatty acids on the glycerol backbone of triglyceride molecules when reacted with glycerol. This process is performed at a high temperature in the presence of an inorganic catalyst, producing an equilibrium mixture consisting of a varying ratio of triglycerides, diglycerides and monoglycerides. The ratio is dependent on the amount of glycerol added to triglyceride and is summarised in the table below:

There are various common applications of emulsifiers in food, with some listed below:

  • Mayonnaise: Permanent emulsion makes the mixture highly stable.
  • Frozen desserts such as ice cream, sorbet, milkshake and frozen mousse: Emulsifiers promote a smoother texture and ensure it does not melt rapidly after serving. Common emulsifiers used include monoglycerides and diglycerides of fatty acids (E471), lecithin (E322), ammonium phosphatide (E442).
  • Chocolate: Emulsifiers can provide the right consistency. Sorbitan tristearate (E492) is an emulsifier which can delay the development of bloom. Bloom is the process that causes the chocolate surface to appear dull or white after being stored at temperatures (refer to the article on chocolate). All chocolate products contain up to 0.5% of lecithin (E322) or ammonium phosphatide (E442).
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