The adding of preservatives is common in the food manufacturing, prepared and fast food to extend the shelf life of perishable foods, such as dairy, soups, fruit-based pie filling and salad creams. Campbell's Soups use sodium and acids as chemical preserving agents for its products, percentages of which can vary depending on the type of soup. Some of its preservatives also double as flavor enhancers—for example many Campbell's Soups contain sodium-rich monosodium glutamate (MSG).
The flavor enhancer Monosodium Glutamate (MSG) is the sodium component of glutamic acid, isolated by chemist Kikunae Ikeda in the early 1900s. Hailing from Japan, the white powdery substance has a similar visual appearance to salt, and is commonly found in pre-made stocks, condiments, powdered and canned soups. Campbell's Soups tends to use MSG in conjunction with other preservatives like sodium in its canned and powdered soups according to the book "The Whole Food Bible: How to Select & Prepare Safe, Healthful Foods" by Christopher Kilham.
Adding sodium to canned soups as a preservative is a common practice – some manufacturers add as much as 1,200 milligrams per can. Campbell's Soup is not exception, with soups containing around 480 to 800 grams per can, according to the article "Salty Spat: Campbell's Sued Over '25 percent Less Sodium' Soup Label." One of the more common sodiums used in Campbell's Soup is potassium sorbate, which is a salt derived from potassium chloride and sorbic acid. This form of preservative is often found in some of its beef stock-based soups and its tomato soup.
Many of Campbell's Soup's chicken and bean based soups carry large amounts of another salt category known as sodium phosphate. This salt group is the umbrella term for any sodium that derives from phosphoric acid, including: monosodium, disodium hydrogen phosphate and trisodium phosphate. The salt is used in canned soups to change the texture of the soup and sometimes help it to keep the oil from separating from the other liquids.
For the preservation of its dairy-based soups, Campbell Soups employs the use of lactic acid. It is a milk acid found in sour milk, molasses and fruit which is produced by exposing carbohydrates to lactic acid bacteria. When adding it to Campbell Soup's "Cream of Mushroom" or "New England Clam Chowder" the acid actually helps to prohibit the growth of fungal or macrobiotic organisms, helping to keep the canned product safe for ingestion.