The chocolate candies M&M's are made of two ingredients: liquid milk chocolate and candy shell. The milk chocolate is made from cocoa butter, sugar and milk. The candy shell is made from corn syrup and sugar. First, the liquid milk chocolate is mixed (some ingredients not included because of proprietary information), then poured into small molds to form the interior of the candy. The chocolate is rolled to make it smooth, then left to cool and harden.
The chocolate centers are transferred from one area in a factory by conveyor belt to the area where the candy shell is applied. Applying the candy shell is called "panning." Each chocolate candy receives several coats of a neutral-color candy coating. The candies are rotated in a large holding unit to ensure each piece receives the same amount of coating. The color is applied last, and each large batch is one particular color so as to produce large numbers of candies.
A finishing machine weighs the candies and packages them into individual bags. The breakdown for regular milk chocolate M&M's generally is: one-third brown, one-eighth yellow, one-eighth red and negligible percentages for green, orange and blue. The machine then heat seals the packages to ensure taste and freshness. Carried on a conveyor belt, the sealed packages are dumped into shipping packages and sealed mechanically.