Final answer:
Pepsin is not found in saliva; it is an enzyme active in the stomach for protein digestion, whereas salivary amylase is the enzyme in saliva responsible for the initiation of carbohydrate digestion.
Step-by-step explanation:
The ingredient in saliva that is not found is pepsin. Saliva contains a mix of water, ions, glycoproteins, enzymes, growth factors, and waste products. The enzyme salivary amylase is responsible for initiating the breakdown of carbohydrates in the mouth. Salivary amylase continues its activity until it is inactivated by stomach acids. Bicarbonate and phosphate ions help maintain the pH of saliva for optimal enzyme activity, with chloride ions being responsible for activating salivary amylase. Salivary mucus aids in lubricating and facilitating the movement of food. Notably, there's no mention of pepsin in the saliva, as it is an enzyme active in the stomach for protein digestion.