The answer is carbohydrates.
Food in the mouth is moistened and lubricated with saliva. Saliva contains an enzyme called salivary amylase.
Salivary amylase is an enzyme that breaks down complex carbohydrates molecules into simple or smaller carbohydrate molecules called maltose. The enzyme acts on carbohydrates in the mouth, initiating the process of digestion.
Salivary amylase is made by the salivary glands in the mouth. Maltose is later converted to glucose in the small intestine by another type of amylase called pancreatic amylase.