Food additives are substances added to food to maintain or improve its safety, freshness, taste, texture, or appearance. They can be natural or synthetic and serve numerous functions. For instance, preservatives such as sodium benzoate extend the shelf life of products by inhibiting the growth of bacteria, mold, and yeast. Emulsifiers, like lecithin, help to maintain a uniform mixture of ingredients that would otherwise separate, such as oil and water in salad dressings.