Deli meats in sandwiches often go unrefrigerated until lunchtime or on deli platters left for hours at room temperature. In these products, as in many others, formulators long have relied on acidifiers to control microbes.
As a product's pH is lowered, the amount of an organic acid in its undissociated form increases. The undissociated forms have the greatest ability to keep microbial growth under control. Some organic acids, such as benzoic and sorbic acid, are extremely effective microbial inhibitors and are considered “preservatives.”