Osmotic stress

Osmotic stress is the stress exerted on cells or tissues when they are subjected to osmotic pressure, typically from high concentrations of salt or sugar in their surroundings. Water is drawn out across the cell membrane, causing plasmolysis in plant tissues and growth inhibition or death in microorganisms that cannot compensate. In food preservation this principle is a deliberate hurdle: salting, sugaring, and drying impose osmotic stress that suppresses spoilage and pathogenic bacteria. Microbes counter it by accumulating compatible solutes, which is why extremely sugary or salty foods can still harbour osmophilic yeasts and Staphylococcus aureus. Effective preservation therefore combines osmotic stress with acidity, heat, or refrigeration to defeat even tolerant organisms.