How Long Does It Take For Food To Digest?
The stomach holds a little under two quarts (1.9 liters) of semi-digested food that stays in the stomach three to five hours. The stomach slowly releases food to the rest of the digestive tract. Fifteen hours or more after the first bite started down the alimentary canal, the final residue of the food is passed along to the rectum and is excreted through the anus as feces.
[Source : The Handy Science Answer Book]