Fermentation: The Science Behind Yogurt

Fermentation: The Science Behind Yogurt

Understanding the microbiology of fermentation From milk to yogurt: A scientific journey Year 10 Biology - Food Technology

What do you already know about fermentation?

Think about foods you've heard are 'fermented' What happens to milk when it goes 'bad'? Have you ever made bread or seen it rise?

What is Fermentation?

A metabolic process where microorganisms break down organic compounds Occurs in the absence of oxygen (anaerobic) Produces energy for microorganisms and useful byproducts for humans Has been used for thousands of years in food preservation

Aerobic vs Anaerobic Respiration

{"left":"Aerobic: Uses oxygen\nProduces CO₂ and water\nYields 38 ATP molecules\nComplete breakdown of glucose","right":"Anaerobic: No oxygen required\nProduces lactic acid or alcohol\nYields only 2 ATP molecules\nIncomplete breakdown of glucose"}

Types of Fermentation

Lactic Acid Fermentation: produces lactic acid (yogurt, cheese) Alcoholic Fermentation: produces ethanol and CO₂ (wine, beer, bread) Acetic Acid Fermentation: produces vinegar Each type uses different microorganisms

The Yogurt Making Process

The Star Players: Yogurt Bacteria

Lactobacillus bulgaricus: rod-shaped bacteria Streptococcus thermophilus: spherical bacteria Work together in symbiotic relationship Convert lactose (milk sugar) into lactic acid Lactic acid gives yogurt its tangy taste and thick texture

Laboratory Investigation: pH Changes

Measure pH of milk before and after fermentation Record temperature throughout the process Observe texture and smell changes Create a data table to track your observations Predict what will happen and test your hypothesis

The Science Behind the Transformation

"Fermentation is one of the oldest biotechnologies, where living organisms transform simple ingredients into complex, nutritious foods through their natural metabolic processes."

Why Fermentation Matters

Food preservation: lactic acid prevents harmful bacteria growth Nutrition: creates probiotics beneficial for gut health Digestibility: breaks down lactose for lactose-intolerant people Sustainability: extends shelf life, reduces food waste Cultural significance: traditional foods worldwide