Bacterial Fermentation

Curriculum Area

New Zealand Curriculum – Level 6, Science (Biology & Chemistry)

• Nature of Science: Understanding how microorganisms contribute to food production through fermentation.
• Living World: Explore the role of microorganisms in ecosystems and human applications.
• Material World: Investigate the chemical processes involved in fermentation.

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Lesson Duration: 30 minutes

Class Size: 30 students
Age Group: Year 11

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Learning Objectives

By the end of this lesson, students will be able to:

1. Define fermentation and explain its role in food/kai production.
2. Identify key microbial players in fermentation, including probiotics and starter cultures.
3. Describe the process of making coconut yoghurt using fermentation.
4. Record fermentation observations and interpret their meaning.
5. Explain how environmental factors influence fermentation.
6. Evaluate how fermentation alters the environment of coconut milk to produce yoghurt.

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Lesson Structure

1. Introduction & Engagement (5 minutes)

Activity: Think-Pair-Share

• Pose a question: "Have you ever eaten food that has been fermented? What do you think happens during the process?"
• Students briefly discuss their ideas in pairs, then share key points with the class.
• Teacher introduces fermentation as a biochemical process where microorganisms break down substances, often to create food products like yoghurt, cheese, bread, or even kānga wai (fermented corn).

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2. What is Fermentation? (5 minutes)

• Explain that fermentation is an anaerobic process (no oxygen) where bacteria and yeast consume sugars and produce acids and/or gases.
• Introduce symbiotic microorganisms, explaining how bacteria and yeast work together in food production.
• Discuss practical applications, using kōrero around kaitiakitanga (guardianship) in traditional Māori fermentation practices such as kānga pirau (fermented corn).

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3. Coconut Yoghurt & Microbiology (5 minutes)

• Define probiotic (beneficial bacteria that aid digestion and immunity).
• Define starter culture (microorganisms added at the beginning of fermentation to trigger the process).
• Describe how coconut yoghurt is made:
  • Start with coconut milk.
  • Add a bacterial starter culture containing Lactobacillus species.
  • Bacteria consume sugars and create lactic acid, thickening the mixture.

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4. Hands-On Experiment: Preparing Coconut Yoghurt (10 minutes)

(Students Work in Small Groups – 5 Students per Group)

1. Set up stations with: small jars, coconut milk, a commercial probiotic capsule (starter culture), and a clean spoon.
2. Steps:
   • Pour coconut milk into a jar.
   • Open the probiotic capsule, sprinkle contents into the milk, and stir.
   • Seal the jar and label it with student names.
3. Explain environmental effects on fermentation:
   • Temperature: Warm environments speed up the process.
   • Time: Fermentation occurs over 12–24 hours.
   • Oxygen levels: Too much exposure may kill beneficial bacteria.
4. Students record initial observations (colour, consistency, smell).

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5. Discussion & Conclusion (5 minutes)

• Each group shares predictions: "What will happen to the yoghurt overnight?"
• Reiterate how bacteria break down sugars and transform the coconut milk into yoghurt.
• Discuss sustainability: Reduced dairy consumption benefits the environment, and fermentation preserves food naturally.

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Assessment & Follow-Up

• Student Portfolio: Each student records observations over 24 hours (changes in texture, smell, pH).
• Class Discussion (Next Lesson): Compare final results across different jars (Was the yoghurt thicker in warmer conditions? Did it taste different?).
• Extension Task: Research and present another fermented food from a different culture.

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Resources & Materials

• Coconut milk
• Probiotic starter cultures (capsule or powder)
• Mason jars
• Spoons & labels
• Printed observation sheets for students

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Teacher Notes

• Store yoghurt samples in a warm, stable environment overnight (e.g., a controlled incubator or warm space).
• Use a pH indicator strip the next lesson to analyse how acidity increases.
• Link lesson to local Māori fermentation traditions to integrate mātauranga Māori.
• Encourage students to taste the yoghurt safely in the next session if they wish (ensuring allergies are checked).

This lesson not only teaches fermentation but also connects science with real-world applications, sustainability, and cultural knowledge, delivering an engaging and memorable experience for students! 🚀