Shelf stable refers to food of a type that would normally be stored refrigerated but which has been processed so that it can be safely stored in a sealed container at room or ambient temperature for a usefully long shelf life. For instance, the first shelf stable formulation of ranch dressing, created in 1983, had a shelf life of 150 days.
Various food preservation and packaging techniques are used to extend a food's shelf life. Decreasing the amount of available water in a product, increasing its acidity, or irradiating or otherwise sterilizing the food and then sealing it in an air-tight container, can all extend a food's shelf life without unacceptably changing its taste or texture.
For some foods alternative ingredients can be used. Common oils and fats become rancid relatively quickly if not refrigerated; replacing them with trans fats (when trans fats are not banned), delays the onset of rancidity - increasing shelf life. This approach was common in industrial-scale factory production in many countries, but research results on the health hazards of trans fats in human diets has made them unacceptable and they are being or already have been banned in many jurisdictions.