The ingredients to make dried pasta usually include water and semolina flour; egg for colour and richness (in some types of pasta), and possibly vegetable juice (such as spinach, beet, tomato, carrot), herbs or spices for colour and flavour. After mixing semolina flour with warm water the dough is kneaded mechanically until it becomes firm and dry. If pasta is to be flavoured, eggs, vegetable juices, and herbs are added at this stage. The dough is then passed into the laminator to be flattened into sheets, then compressed by a vacuum mixer-machine to clear out air bubbles and excess water from the dough until the moisture content is reduced to 12%. Next, the dough is processed in a steamer to kill any bacteria it may contain.