Tapioca, cornstarch, SAGO, and YOLK are all common ingredients used as thickeners for pudding. TAPIOCA is a starch extracted from the cassava root and is often used in puddings and other desserts. Cornstarch is a powder made from the endosperm of corn kernels and is also used to thicken sauces, gravies, and puddings. SAGO is a starch extracted from the spongy center, or pith, of various tropical palm stems and is used to thicken soups, stews, and puddings. Finally, egg yolks are a common ingredient used to thicken custards and other creamy desserts.