Food remains in the stomach for 4-5 hours. During this time, it mixes thoroughly with the acidic gastric juice by the churning movements of the muscular wall of the stomach and is now called the chyme.
Digestion in the stomach:
A. Proenzyme pepsinogen -----(HCl)---- → Pepsin (active enzyme).
B. Proteins ------- (Pepsin, pH = 1.8) ---- → Proteoses and peptones (peptides).
C. Rennin (a proteolytic enzyme in gastric juice of infants) helps in the digestion of milk proteins.
D. Lipases are also secreted in small amounts.