Why Is There Little or No Digestion of Starch in the Stomach?

There is little to no digestion of starch in the stomach because the necessary enzymes do not function well in an acidic environment, according to class materials from the University of Maine. Salivary amylase, an enzyme, begins to break down starch as soon as the starch mixes with saliva, says Dr. Michael Gregory.

The pH of the stomach ranges from 1.0 to 3.0, but it is usually somewhere around 2.0, reports UCSB ScienceLine. Saliva has a pH ranging from 6.5 to 7.5 due to the presence of bicarbonate ions that act as buffers, says Dr. Gregory. This pH range is close to neutral, allowing salivary amylase to begin the process of breaking down starch into maltose before food reaches the stomach. Chewing breaks the food apart, speeding up chemical digestion. Then the mucins in saliva bind the chewed food together to form a bolus.

Digestion continues when the food bolus travels through the esophagus and into the stomach. Protein digestion begins when the hydrochloric acid in the stomach triggers the action of pepsin, a protein-digesting enzyme. Once food reaches the small intestine, it mixes with digestive juices and continues to move through the intestinal tract. The small intestine is where the byproducts of carbohydrates, proteins and fats are absorbed, according to Midlands Technical College.