There are many examples of both direct additives and indirect additives. Examples of direct additives that help maintain or improve freshness and safety include:

• Antimicrobial agents. Help prevent microbes that may cause foodborne illness. Salt and sugar are the most commonly used antimicrobial agents. Salt helps preserve meat and fish while sugar used as part of the canning process can help preserve canned fruits, frozen fruits and jams and jellies. Both salt and sugar absorb water so that it is not available to microbes. Potassium sorbate and sodium propionate help preserve baked goods, cheeses, beverages, mayonnaise and margarine. Nitrates are added to foods to preserve color, enhance flavor by slowing rancidity (decomposition of fats) and protect against bacterial growth (including the bacteria that cause botulism).
  
  
• Antioxidants. Prevent oxidation, the process that causes rancidity and flavor changes in foods, fats and oils upon exposure to oxygen. Antioxidants include vitamin C and vitamin E. Sulfites are antioxidants that prevent oxidation in processed foods, alcohol and drugs. They cannot be used on foods that are eaten raw (except grapes) because this may cause adverse reactions. They also cannot be used in foods that are important sources of thiamin (e.g., enriched grain products), because sulfites are known to destroy this vitamin. Foods and drugs that contain sulfites must indicate the additive on the labeling. This may be referred to as sulfur dioxide, sodium sulfite, sodium bisulfite, sodium metabisulfite and potassium metabisulfite. The antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are widely used to prevent spoiling, and rancidity in baked goods, snack foods and breakfast cereals.

Examples of direct additives that help improve taste, texture and appearance include:

• Natural flavors, artificial flavors and flavor enhancers. These substances help foods taste better. Natural flavors include spices, herbs, essential oils, fruits and fruit juices. Some spices provide antioxidant protection. Artificial flavors include artificial sweeteners such aspartame. Flavor enhancers are products that help bring out a food’s sweet, salty, bitter or sour taste. Examples include monosodium glutamate (MSG).
  
  
• Food preparation and processing additives. These products help foods to maintain a certain consistency. For example, emulsifiers help keep mayonnaise stable and allow powdered coffee cream to dissolve more easily. Gums are used to thicken foods and help form gels. Examples include xanthan gum, bicarbonates and acids. Anti-caking agents keep food from absorbing moisture so it does not clump together, while leavening agents (e.g., yeast) release acids during heating that react with baking soda to help foods to rise.
  
  
• Nutrient additives. Nutrients are sometimes added to fortify or maintain the nutritional quality of foods. These include nutrients added to refined grains (riboflavin, thiamine, folic acid, niacin, iron), the iodine added to salt, the vitamins A and D added to milk, and the nutrients added to fortified breakfast cereals.
  
  
• Colors. Both synthetic colors and colors derived from natural pigments may be added to foods to improve appearance. Most processed foods contain color additives. For example, margarine would not be yellow without color additives. Color additives may be used to offset color loss resulting from exposure to air, light, moisture, temperature extremes and storage conditions. They also may be used to correct natural variations in color, enhance naturally occurring colors and provide color to foods (e.g., foods that naturally lack an appealing color).
  
  Color additives are divided into two categories: certified colors and colors exempt from certification. Certified colors are synthetic substances that provide a uniform color to foods. Most of these colors do not change a food’s taste. They are often used to give more intense color to food and to create various hues.
  
  Colors that are exempt from certification are derived from natural sources (e.g., animals, vegetables or minerals). They typically are more expensive than certified colors and may alter the taste of a food. Annatto extract and dehydrated beets are examples. In the United States, 33 colors have been approved for use and nine of those are synthetic. The manufacturer and the FDA test every batch of synthetic color for purity.
  
  Examples of artificial colors include two forms of blue (brilliant blue and indigotine), two reds (allura red and erythrosine), two yellows (tartrazine and sunset yellow) and a green (fast green). Natural-color additives include annatto (yellow), caramel (yellowish brown), carotenoids (yellowish orange), dehydrated beets (reddish brown) and grape skins (red, green).

Indirect additives are usually present in tiny amounts and may include bits of plastic, glass, paper, tin and chemicals from processing (e.g., the solvent used to decaffeinate coffee). Examples of indirect additives found in foods include:

• Acrylamide. A compound that forms when foods rich in carbohydrates are cooked at high temperatures. For example, potatoes formed into French fries contain acrylamide. This substance has been shown to cause cancer in animals, but scientists are unsure of whether or not there is enough acrylamide in foods to pose a health threat to humans. FDA researchers are studying this question.
  
  
• Dioxins. Packaging made of bleached paper can contaminate foods with tiny quantities of dioxins. These compounds form during chlorine treatment of wood pulp during the manufacturing of paper. Packaging that may contain dioxins include coffee filters, milk cartons, paper plates, and frozen-food packages. However, these amounts are believed to be too low to cause a health threat.
  
  
• Hormones. The FDA has approved a dozen hormones for use in food-producing animals. This produces leaner meats, and higher outputs of milk from dairy cows. Traces of hormones such as bovine growth hormone (BGH) find their way into the foods and milk people consume. However, organizations such as the National Institutes of Health (NIH) have declared that meat and milk from animals treated with hormones is as safe as that of untreated animals.
  
  
• Antibiotics. Similar to hormones, antibiotics given to animals may eventually be found in foods in trace amounts. Some people who have allergies to antibiotics may experience an allergic reaction as a result. For most other people, the levels of antibiotics in these foods pose no threat. The FDA requires a specified time between the times an animal is treated with antibiotics and when the animal is slaughtered. This time should allow for the drug to be metabolized in the animal’s body and excreted so only a minimal amount is passed into food.
  
  
• Microwave packaging. Microwave products that contain “active packaging” are used as part of the cooking process (e.g., frozen pizzas). In such instances, packaging materials may be found in the foods. The FDA requires the manufacturers prove that this packaging is safe for human consumption. Packaging that simply holds the food while it cooks also may pass into the food. This, too, is safe according to the FDA, but the packaging should not be reused.
  
  
• Decaffeinated coffee. Methylene chloride is used to remove caffeine from coffee. This process leaves this chemical in the coffee. The levels that are present pose no threat to people, according to the FDA. For those who remain concerned, decaffeinated coffee is available in formulations where the caffeine is removed during a steam process.