Lecithin's talent comes from its amphipathic nature.(1) The compound's hydrophilic polar head dissolves in water while its hydrophobic polar tail dissolves in the triglycerides, thus, acting in a way of suspending triglycerides in water.(1p568)
As an emulsifier in ice cream, lecithin keeps ice cream smooth with fat globules evenly distributed throughout the solution.(2) It serves to bring fat and ice crystals together, which normally don't mix. Before commercial lecithin was available, egg yolks were used.(2)
Another useful application:
Want to know how to make your own salt air foam to a homemade margarita? The secret is soy lecithin. You can buy it at any health food store and mix about a teaspoon with water, salt and lime juice.
1. Denniston, KJ, Topping, JJ & Caret, RL. General, Organic, And Biochemistry, 5th ed. New York: McGraw Hill; 2007, p568.
2. Halford, B. Ice cream: The finer points of physical chemistry and flavor release make this favorite treat so sweet. Science & Technology. 2004;82(45):51. Available at: http://pubs.acs.org/cen/whatstuff/stuff/8245icecream.html. Accessed on November 1, 2008.