How does coffee remain frothy?

A cup of hot coffee with a thick layer of froth on it is delightful when you serve it sprinkled with a little chocolate powder. A pretty sight too. But what makes the froth and keeps it? 

When you beat coffee powder with granulated sugar with a few drops of water, there are two things that happen…the sugar granules mingle with the coffee grains as they melt allowing for the flavours to develop fully. So by the time the hot milk is ready to be poured into this mixture, the full flavour is ready! Secondly, while beating the coffee powder with the sugar a lot of air is incorporated. This air forms the bubbly froth on the top of the cup. For best results, use full cream milk. The froth is thicker, creamier and lasts till you finish drinking it all up!

Unfortunately, frothy coffee is not possible for those who favour skimmed milk! There is no fat to sustain the air bubbles inspite of beating the coffee with sugar. But, yes, the coffee flavour will be much stronger.