Cream is the part of milk that contains the butterfat which naturally rises to the top. It is separated by centrifical force from the milk. The degree of butterfat in the cream depends on the speed of the centrifuge.
According to Dairy Australia "Cream is categorised according to its milk fat content and comes in two forms ? pure and treated. Cream must contain no less than 350g/kg of milk fat or 35% milk fat. It may be adjusted by the addition of milk or products obtained from milk.
"Rich or Double Cream Does not contain any thickening agents and usually has a fat content of around 48% or more.
"Regular or Pure Cream Does not usually contain any thickening agents and has a fat content of around 40%.
"Thickened Cream With 35% contains additives such as gelatin, vegetable gum or other modifying agents. The additives act as thickening agents, making it easier to whip and less likely to separate or curdle.
"18% Milk Fat Content May be called Lite, Lite Thick (thickened).
"Sour Cream To make sour cream, a culture is added and the cream is heated to about 20?C for 12?14 hours. The lactic acid produced in this process gives a slightly sour taste and a thicker than normal consistency."