Making ice cream - it's physical chemistry Look at ice cream
magnified several hundred times in a scanning electron
microscope and you will see that it has a complex structure on
length scales of 1 µm to 1 mm (Fig 1). There are ice crystals
(ca 30 per cent by volume), air bubbles (50 per cent) and fat
droplets (5 per cent) from the cream, held together by a viscous
sugar solution (15 per cent). Ice cream thus contains all three
states of matter simultaneously and is both a foam and an oil-
in-water emulsion. The quality of ice cream depends on its
microstructure: small ice crystals and air bubbles give the ice
cream a smooth, soft texture. If the ice crystals are too large,
the ice cream becomes gritty and unpleasant to eat. Creating
this microstructure is the key to making good ice cream - and to
understand how to do this, you need to know some physical
chemistry. Fig 1 A scanning electron micrograph of ice cream ©
Courtesy of M. Kirkland, Unilever R&D Colworth Creating a
microstructure The first step is to k