One of the most widely used colors is caramel, the color of burnt sugar. There are many different types of caramel color, each engineered to serve a particular purpose in food chemistry. They are all based on the cooking of sugars and starches. Sometimes acids such as acetic acid, citric acid, lactic acid, or phosphoric acid, are used to break the bonds between sugars to create invert sugars, or to make sugars from starches, before the sugars are raised to a higher temperature for carmelization. The heat is carefully controlled during carmelization to get the right products from the reaction. Besides acids, alkalies and salts may be used to further control the process. Caramel color is a colloid, a mixture in which solid particles are suspended in water. The particles in colloids have electric charges that keep the particles from clumping together and settling out of solution. The charges can be positive or negative. If a negative coloid is added to a product that has positive colloidal particles in it, the two will attract one another and clump up, making the product cloudy. Caramel color can be made with either positively or negatively charged particles. This allows manufacturers to use negative colloidal caramel in acidic soft drinks, and positive in beers and soy sauces. Beer has positively charged proteins suspended in it, and soy sauce has a high salt content that requires the more salt-tolerant positive caramel color. Caramel color is an emulsifying agent as well as a colorant. In soft drinks, it helps keep the flavor oils suspended in the solution. In chocolate milk, the muddy color of caramel is darkened by the addition of FD&C Red #40 to give what the industry refers to as a "Dutch" chocolate shade. Blues and yellows are sometimes used to give a more brown color. Caramel color is added to baked goods, to poultry, to milk to give an "eggnog" color, to malt vinegars, canned meats, syrups, and soups, stews, and gravies. If caramel color is made in North America it is likely to be gluten-free. The problem with caramel color is that it may or may not contain gluten depending on how it is manufactured. In the USA caramel color must conform with the FDA standard of identity from 21CFR CH.1. This statute says: "the color additive caramel is the dark-brown liquid or solid material resulting from the carefully controlled heat treatment of the following food-grade carbohydrates: Dextrose (corn sugar), invert sugar, lactose (milk sugar), malt syrup (usually from barley malt), molasses (from cane), starch hydrolysates and fractions thereof (can include wheat), sucrose (cane or beet)." Also, acids, alkalis and salts are listed as additives which may be employed to assist the caramelization process.