Edexcel iGCSE Biology-6.7 Role of Bacteria in Yoghurt Production- Study Notes- New Syllabus

Role of Bacteria (Lactobacillus) in Yoghurt Production

🌱 Introduction

Yoghurt is a fermented milk product made using specific bacteria.
The main bacteria used: Lactobacillus spp.
These bacteria convert milk sugars into lactic acid through fermentation.
Lactic acid thickens milk and gives yoghurt its sour taste.

⚡ Process of Yoghurt Production

• Milk Preparation:
  Fresh milk is pasteurized → kills harmful bacteria.
  Milk is cooled to ~40–45°C → ideal for bacterial growth.
• Inoculation with Lactobacillus:
  Starter culture of Lactobacillus is added.
  Bacteria ferment lactose (milk sugar) → lactic acid.
• Fermentation:
  Lactic acid lowers pH of milk → causes proteins to coagulate.
  Milk thickens → develops smooth, creamy texture.
• Cooling & Storage:
  Fermentation is stopped by cooling.
  Yoghurt is then ready for consumption.

🌾 Importance of Lactobacillus

• Preservation: Lactic acid inhibits growth of harmful microbes
• Texture & Taste: Gives thick, creamy consistency and sour flavour
• Health Benefits:
  • Acts as probiotics → improves gut health
  • Enhances digestibility of milk proteins and lactose

📊 Summary Table

💡 Quick Recap 
Lactobacillus = key bacteria in yoghurt → ferments lactose
Sugar → Lactic acid → thick, sour yoghurt
Low pH preserves yoghurt & improves gut health
🧠 Mnemonic: “Lacto Loves Milk → Acid Thickens & Protects”