Edexcel iGCSE Biology-6.5 Yeast in Food Production- Study Notes- New Syllabus

Role of Yeast in Food Production (Including Bread)

🌱 Introduction

Yeast is a unicellular fungus widely used in food production due to its ability to ferment sugars.
Key products made using yeast:

• Bread
• Alcoholic beverages (beer, wine)
• Other fermented foods (some pastries)

⚡ How Yeast Works in Bread Making

• Fermentation Process:
  Yeast feeds on sugars in flour or dough.
  Produces carbon dioxide (CO₂) and ethanol:
  Sugar → CO₂ + Ethanol + Energy
  CO₂ forms bubbles in dough, making it rise and become soft.
• Baking Process:
  Dough is baked → ethanol evaporates.
  CO₂ bubbles → light, fluffy bread.

🌾 Steps in Bread Making with Yeast

• Mix flour, water, yeast, sugar, and salt
• Knead the dough → develops gluten
• Leave dough to rise → yeast ferments sugar → CO₂ forms
• Bake in oven → CO₂ trapped → bread rises
• Final product → soft, spongy bread

🧠 Other Roles of Yeast in Food Production

• Alcoholic beverages: Ferments sugars to produce ethanol
• Fermented foods: Enhances flavour and texture
• Nutritional benefits: Yeast adds vitamins (B-complex) and protein

📊 Summary Table

💡 Quick Recap 
Yeast = unicellular fungus → ferments sugars
Sugar → CO₂ + Ethanol → energy
CO₂ makes bread rise, ethanol evaporates during baking
🧠 Mnemonic: “Yeast Eats Sugar → CO₂ Up → Bread Puff”