Which digestive organ mechanically and chemically transforms a food bolus into chyme?

Mechanically and chemically, stomach transforms a food bolus into chyme. The bolus of food is carried down the oesophagus by peristalsis, and finally reaches the stomach. The stomach stores food for 4 - 5 hours, then the food mixes thoroughly with the acidic gastric juices of the stomach by the churning movements of its muscular wall and is called chyme.