Food Growth Flashcards
What are intrinsic factors affecting microbial growth?
pH,
water activity (Aw)
oxidation-reduction potential,
gases in the atmosphere,
chemicals,
nutrients,
food structure,
and natural microbial inhibitors.
What are extrinsic factors affecting microbial growth?
Temperature,
gases in the atmosphere,
oxidation-reduction potential,
and interactions between microorganisms.
Why is pH important in microbial growth?
determines which microorganisms can grow; most pathogens do not grow below pH 3.8.
Which microorganisms are most tolerant of extreme pH levels?
Molds (0-11) and Yeasts (1.5-8.5).
What is water activity (Aw), and why is it important?
It measures available water for microbial growth. Most fresh foods have Aw > 0.99.
What are the minimum Aw levels for spoilage organisms?
Bacteria: 0.91, Yeasts: 0.88, Molds: 0.80.
How does oxidation-reduction potential affect microbial growth?
Oxygen availability determines if microorganisms grow better under aerobic or anaerobic conditions.
What are the four temperature classifications of microorganisms?
• Psychrophiles (0-15°C, cold-loving)
• Mesophiles (10-45°C, moderate temperature)
• Thermophiles (40-70°C, heat-loving)
• Extreme thermophiles (65-110°C)
What nutrients do microorganisms require?
Carbohydrates, proteins, fats, vitamins, and minerals.
What are some naturally occurring microbial inhibitors?
Lysozyme (egg white), lactoperoxidase (milk), allicin (garlic), thymol (thyme).
How do gases affect microbial growth?
Directly (toxic effects, e.g., CO₂, O₃) or indirectly (modifying gas composition, e.g., modified atmosphere packaging).
What are the two main types of microbial interactions?
• Symbiotic: Microorganisms support each other’s growth. Example: Yogurt production.
• Antagonistic: One microorganism inhibits another, often by producing antimicrobial compounds.
What is food spoilage?
Uncontrolled changes in physical, chemical, or microbiological characteristics of food.
How is food spoilage different from food poisoning?
Spoiled food is usually rejected before ingestion and is not necessarily unsafe, whereas food poisoning occurs when contaminated food is consumed.
What are the five main causes of food spoilage?
- Microbiological (bacteria, fungi, viruses)
- Biological (rodents, insects)
- Enzymatic Reactions (browning, lipolysis)
- Chemical Reactions (oxidation)
- Physical Damage (triggers other spoilage reactions)
What are the two main types of foodborne diseases?
- Food intoxication: Caused by consuming preformed toxins.
- Food infection: Caused by ingesting pathogenic microorganisms.
What is the hurdle concept in food safety?
Using a combination of intrinsic and extrinsic factors to inhibit microbial growth with minimal food processing.
