Icing: A sweet mixture of sugar and other ingredients used to coat and fill cakes, cookies and other pastries. The other ingredients may include butter or other shortening, milk, eggs and flavorings such as vanilla extract, chocolate or citrus. Frosting may be uncooked (simple buttercream, made by creaming shortening with sugar) or cooked (boiled frosting, in which hot sugar syrup is combined with egg white, and Italian and French buttercream, in which hot sugar syrup is combined with whipped egg whites or yolks, respectively, and butter). Frosting can be very thick and unctuous or thin and glossy, but it must be thick enough to adhere to the surface of the item being coated. Depending on its consistency it may be spread in a smooth, even layer, swirled with the back of a spoon of spatula, or piped in decorative shapes and designs. Irradiated foods: Irradiation is the process of exposing foods to ionizing radiation to destroy bacteria or slow ripening or maturation, thereby preventing some kinds of microbial contamination and extending the treated item's shelf-life. In the United States foods treated with irradiation must have labels that include a radura, the international symbol for irradiation, and the words "treated by irradiation" or "treated with radiation." Products that include irradiated ingredients, such as spices, do not have to be labeled. The USDA has approved a wide variety of foods for irradiation, including spices and dry vegetable seasoning, fruits and vegetables, fruit and vegetable juices, pork, beef, lamb, poultry and eggs, and approval for other items is pending. Many of the approved items are not yet on the market; about 10% of the spices and less than 1% of poultry and pork on the market have been irradiated, although those percentages vary from state to state. Some consumer and other groups oppose food irradiation, claiming that the long-term effects have not been sufficiently studied and that the process destroys vitamins and other nutrients, creates new and as yet unstudied chemicals in the treated foods and masks unsanitary conditions in processing plants. The American Dietetic Association and The World Health Organization are two of the groups that approve of irradiation.