Rancidity and Food Preservation

📚 Key Concepts

🔹 Real-Life Example

When you leave butter or cooking oil exposed to air for a long time, it develops a bad smell and taste – it becomes “rancid.” This happens because the fats and oils react with oxygen in the air. That’s why potato chips are packed in nitrogen gas instead of air, and why many food packages say “store in a cool, dry place.”

Rancidity: When fats and oils are oxidised, they become rancid and their smell and taste change. Rancidity is the chemical decomposition of fats, oils and other lipids.

🧪 Important Concepts

🔸 Types of Rancidity

1. Oxidative Rancidity: Reaction with oxygen

2. Hydrolytic Rancidity: Reaction with water

3. Microbial Rancidity: Caused by bacteria

🔸 Prevention Methods

1. Antioxidants: BHT, BHA (preservatives)

2. Airtight containers: Prevent oxygen contact

3. Refrigeration: Slow down chemical reactions

4. Nitrogen packaging: Replace air with inert nitrogen

5. Vacuum packaging: Remove air completely

🔹 Common Antioxidants

• Natural: Vitamin C, Vitamin E, Citric acid
• Synthetic: BHT (Butylated Hydroxytoluene), BHA

🔍 Advanced: Why Nitrogen?

Nitrogen is chemically inert (unreactive) and makes up 78% of air. By replacing oxygen with nitrogen in food packaging, oxidation reactions that cause rancidity are prevented.