Brand marketers want their new beverages to be "shelf stable," "all natural" and "made without chemical preservatives." Beverage developers hear these product requirements each time they embark on a new beverage development project.
Beverages typically have been preserved with chemicals such as sodium, potassium or calcium salts of benzoates and sorbates, resulting in the beverage as benzoic acid or sorbic acid. The preservative effect of these chemicals relates to the pH of the product. The "pH" means the "Potential of Hydrogen" and is a measure of the acidity and alkalinity of a solution. If the "Potential of Hydrogen" is high with a lot of hydrogen ions in the solution, then the product is acid and has a low pH. Alternatively, if the concentration of hydrogen ions is low, then the product is alkaline and the pH is high.
It just so happens that a high concentration of hydrogen ions in a solution can have a germicidal effect on microorganisms. That's why fruit juices have self-preserving properties where microorganisms are inhibited by the hydrogen ion concentration in the juice. These hydrogen ions come from organic acids present in the fruit that reduces the pH of the juice.
Understanding this, the beverage developer through pH control can start to formulate a product that will have properties necessary to eliminate the use of chemical preservatives and maintain shelf stability in the marketplace. We can get back to basics and use these organic acids that are naturally occurring in fruit juices. Not only do the organic acids drive the pH of the beverage down and act as a preservative, but they contribute to the sweetness, tartness and "thirst-quenching" properties of the product as well.
Beverages can be formulated with an array of these compounds. Some examples include citric acid, ascorbic acid, lactic acid, tartaric acid, malic acid, phosphoric acid and fumaric acid. Each of these organic acids have specific properties unto themselves that are synergistic with specific beverage flavors resulting in beneficial sensory properties. Beneficial combinations may include phosphoric acid in cola, tartaric acid with tea or malic acid with apple.
But the world is not perfect, and pH control may have some limiting factors. One is flavor. If the product is too acidic in taste, it may be detrimental to overall acceptability. In addition, some bacteria may survive lower pH's and cause shelf life problems. However, the beverage developer can overcome these imperfections by combining pH control with the appropriate process and package to ensure shelf stability to create a product without chemical preservatives. Carbonation, refrigeration, aseptic processing and packaging, hot pack and pasteurizing all assist in giving pH controlled beverages shelf stability.
Organic acids are available as ingredients both naturally occurring or synthesized. The pH control achieved by using ingredients such as concentrates of lime, lemon, grapefruit, cranberry, white grape or apple provides a cross section of a the organic acids that have synergy with various beverage flavors.
Phil Katz is president of the Food and Pharmaceutical Division of Herbert V. Shuster Inc., a consumer products R&D and testing firm with facilities in Quincy, Mass., and Atlanta.