The enzyme ptyalin is present in which of the following?

Each digestive fluid in the human digestive tract is secreted by a specific gland and carries enzymes suited to breaking down particular nutrients. Saliva, secreted by the salivary glands into the mouth, contains the enzyme ptyalin (salivary amylase), which hydrolyses starch into maltose and begins carbohydrate digestion even before food reaches the stomach.

Since ptyalin is specifically the starch-digesting enzyme secreted with saliva in the mouth, it is present in Saliva juice.

Checking the other digestive juices confirms that none of them contain ptyalin:

• Gastric juice — secreted by gastric glands in the stomach; contains pepsin and hydrochloric acid, which digest proteins, not starch.

• Pancreatic juice — secreted by the pancreas into the duodenum; contains trypsin, lipase, and pancreatic amylase, which act on proteins, fats, and carbohydrates at a later digestive stage, not in the mouth.

• Bile juice — produced by the liver and stored in the gallbladder; contains no digestive enzymes and only emulsifies fats.

Therefore, Saliva juice is the option that contains the enzyme ptyalin.