How does a refrigerator preserve foods?
Bacterial activity is inhibited at low temperatures. When they're cold, their chemical processes slow down, so they aren't able to reproduce and eat like they do at room temperature, so the food lasts longer.
Sugar is used to preserve fruits as jam/jelly. Salt is used to preserve foods such as fish and meats like bacon. Vinegar is used to preserve many different foods such as onions, cabbage, beetroot etc. Other methods of preserving include drying and smoking but these are not specifically answering your question. Examples are mushrooms and meats.