How come ranch dressing can sit on shelves in grocery store at room temp without going bad. When open it says refrigerate.
Nash County North Carolina
Many items that you purchase are labeled 'refrigerate after opening', this is due to how products are processed and sealed.
When the products are sealed, the amount of oxygen available to the product is reduced, something that most pathogens need to grow. When that seal is broken, and the food has access to all the oxygen it wants, thus allowing pathogens to grow. BUT if we refrigerate that product, it will reduce the growth of pathogens. Pathogens are like most people; to survive, they want good climate, a food source, and, comfy conditions. Reducing oxygen and cooling make it uncomfortable for most pathogens.
The way that we process foods is to help control pathogen growth, spoilage, and food quality.