Food Microbiology Exam (2)

  • Spontaneous Generation: Disproven idea that life arises from non-living matter.

  • Germ Theory: Microbes cause diseases.

  • Scientific Method: Observation → Hypothesis → Experiment → Conclusion.

  • Taxonomy: Classification of organisms (Domain, kingdom, etc.).

  • Infectious Disease Terms:

    • Reservoir: Where a pathogen naturally lives.

    • Source: Immediate origin of infection.

  • Food Infection vs. Food Intoxication:

    • Food Infection: Caused by consuming live microbes (e.g., salmonella).

    • Food Intoxication: Caused by toxins produced by microbes (e.g., staphylococcus aureus).

  • Molds and Mycotoxins:

    • Fungal pathogens: Found in soil, plants, and decaying matter; humans are relatively resistant.

    • Thermal dimorphism: Ability to grow as yeast (warm) or mold (cold).

  • Portals of Entry:

    1. Skin (cutaneous entry): Through cuts, abrasions, or wounds.

    2. Respiratory tract (inhalation): Inhalation of fungal spores from the air.

    3. Gastrointestinal tract (ingestion): Consumption of contaminated food or water.

    4. Mucous membrane (eye, mouth, nose): Early entry through mucosal surfaces during exposure to contaminated environments.

    5. Systemic (opportunistic entry): Occurs in immunocompromised individuals, leading to systemic fungal infections.

  • Mycotoxins Overview:

    • Aflatoxins: Found in grains, peanuts; produced by Aspergillus; stable in heat; causes liver damage.

    • Ochratoxin: Found in cereals, coffee (Aspergillus and Penicillium); targets kidney.

    • Patulin: Found in apples; causes gastrointestinal issues.

    • Fumonisins: Found in corn; affects the nervous system.

    • Deoxynivalenol (DON): Found in wheat; causes vomiting.

  • Mycotoxin Control:

    • Mycotoxin production in storage:

      • Moisture Content: High water activity (aw > 0.7) promotes mold growth.

      • Temperature: Warm temperatures (25-30°C) accelerate production.

      • Oxygen Availability: Aerobic conditions encourage fungal growth.

      • Storage Time: Longer storage increases the risk of mycotoxin buildup.

      • Grain Damage: Damaged or improperly harvested grains are more susceptible.

    • Mycotoxin control:

      • Pre-Harvest Measures:

        • Use resistant crop varieties.

        • Apply fungicides when necessary.

        • Practice crop rotation and proper field management.

      • Harvesting Measures:

        • Harvest crops at the correct maturity stage.

        • Minimize damage during harvesting.

      • Post-Harvest Storage and Handling:

        • Drying: Reduce moisture content to below 13% for grains.

        • Cooling: Store products at low temperatures (< 10°C).

        • Aeration: Ensure proper ventilation to reduce moisture buildup.

        • Packaging: Use airtight, moisture-proof containers.

        • Sorting and Cleaning: Remove contaminated or damaged grains.

      • Processing and Treatment:

        • Physical Methods: Heat treatment (roasting), UV radiation, and irradiation can reduce mycotoxins.

        • Chemical Methods: Additives like organic acids (e.g., propionic acid) or preservatives (e.g., sulfites) can inhibit fungal growth.

        • Biological Methods: Use of beneficial microbes to degrade mycotoxins.

  • Viruses:

    • Characteristics of viruses:

      • Size: 20-300 nm.

      • Structure: Capsids (protein coat), envelope (lipid layer), spikes (attachment).

    • Virus multiplication steps:

      1. Adsorption: The virus binds to host receptors.

      2. Penetration: Enveloped (fusion or endocytosis) and naked (endocytosis only).

      3. Synthesis: DNA viruses replicate in the nucleus, RNA viruses in the cytoplasm.

      4. Release: Budding (enveloped) or lysis (naked).

    • Key Takeaways:

      • Naked Viruses: More environmentally resistant, spread through harsh environments.

      • Enveloped Viruses: More vulnerable to external conditions but better at evading the immune system.

  • Potential Food Sources for Viruses:

    • Fresh Produce: Leafy greens, berries (due to water contamination).

    • Shellfish: Oysters, clams, and mussels (filter-feeding can concentrate viruses).

    • Ready-to-Eat Foods: Salads, sandwiches, and deli items (via infected food handlers).

    • Contaminated Water: Used for irrigation or as drinking water.

  • Control of Viruses in Foods:

    • Good Hygiene Practices: Handwashing by food handlers, proper sanitation in food processing environments.

    • Safe Food Handling: Avoid cross-contamination between raw and cooked foods.

    • Cooking and Heating: Cook foods to appropriate temperatures to inactivate viruses (e.g., 85-90°C for Norovirus).

    • Water Quality Control: Use clean water for irrigation, processing, and consumption.

    • Monitoring and Testing: Regular testing for viral contamination in food production facilities.