Food Preservation and Storage: notes

Why food spoils

• Microorganisms: bacteria, yeast and moulds need warmth, moisture, food and time.
• Enzymes: cause ripening, then rotting.

Methods

• Drying: removes water. Used for matemba, kapenta and vegetables (mufushwa).
• Salting and smoking: salt draws water out; smoke dries and flavours.
• Freezing: at minus 18 degrees Celsius germs stop growing but are not killed.
• Canning and bottling: heat kills germs, then a seal keeps new ones out.
• Pickling and jam: vinegar, or a high concentration of sugar, stops growth.
• Pasteurising: milk is heated to kill harmful bacteria.

Storage

• Stock rotation: use the oldest stock first.
• Dry foods: cool, dry, covered containers. Fresh foods: fridge at 5 degrees Celsius or below.