Green papaya is another way of saying "unripe papaya." This oblong green fruit can vary greatly in size and shape but are usually oblong, and range from about 1 foot to 1 1/2 feet in length. To use a green papaya, remove the green outer skin. Inside you will find a milky, sticky sap. Inside the sap is an enzyme that aids in the process of breaking down proteins. For this reason, it is often used in Thai cooking, in both a cooked and raw form, for tenderizing meats.