Based on the book by Stephen T. Beckett "Industrial Chocolate Manufacture and Use", lactones and methyl ketones are formed when milk fat is heated. this is very important in the flavor of milk chocolate. When the low melting triglycerides in milk are mixed with cocoa butter, the triglycerides have a diluting effect on the cocoa butter, softening it. it is also shown that milk has lipases which hydrolyse triglyceride molecules that release fatty acids. These fatty acids create a buttery and creamy flavor in the milk chocolate. sourceT. Beckett, Stephen . "Ingridents from milk ." Industrial chocolate manufacture and use. 4th ed. Malden, MA: Blackwell Publishing, 2009. 82, 83, 84, 85. Print.