Some foods are digested quite quickly unlike many others. Fruits, for instance, are pretty fast to digest (that takes only an hour after their consumption) since they go directly into the small intestine. The reason is that they contain ferments which boost the assimilation.
Digestion - a sequential process of breaking down carbohydrates, protein as well as fat by means of enzymes, consisting in saliva, gastric juice, pancreatic and intestinal juices and bile as well. Enzymes are also known as ferments, the biological role of which is to speed up the biochemical processes.