Food Preservation and Spoilage

📚 Key Concepts

🔹 Microbial Food Spoilage

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How Microorganisms Spoil Food:

  • Bacterial growth: Rapid multiplication in favorable conditions
  • Enzyme action: Breaking down food components
  • Toxin production: Harmful chemicals produced
  • Physical changes: Color, texture, smell changes

Favorable Conditions for Spoilage:

  • Temperature: 20-40°C (optimal growth range)
  • Moisture: High water content
  • pH: Neutral pH (6-8)
  • Oxygen: Varies by organism type
  • Nutrients: Rich food sources

🔹 Food Preservation Methods

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Traditional Methods:

1. Salt Preservation

  • Mechanism: Dehydrates microorganisms
  • Applications: Pickles, cured meats
  • Effectiveness: Prevents bacterial growth

2. Sugar Preservation

  • Mechanism: Creates hypertonic environment
  • Applications: Jams, jellies, honey
  • Effectiveness: Inhibits microbial growth

3. Drying/Dehydration

  • Mechanism: Removes water needed for growth
  • Applications: Dried fruits, jerky
  • Effectiveness: Long-term preservation

4. Fermentation

  • Mechanism: Beneficial microbes outcompete harmful ones
  • Applications: Yogurt, sauerkraut, kimchi
  • Effectiveness: Creates acidic environment

Modern Methods:

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1. Refrigeration

  • Temperature: 0-4°C
  • Effect: Slows microbial growth
  • Duration: Days to weeks

2. Freezing

  • Temperature: Below -18°C
  • Effect: Stops microbial growth
  • Duration: Months to years

3. Pasteurization

  • Process: Heat treatment (60-85°C)
  • Effect: Kills harmful microorganisms
  • Applications: Milk, juices

4. Sterilization

  • Process: High heat (121°C) or chemicals
  • Effect: Kills all microorganisms
  • Applications: Canned foods, medical equipment