Podcast
Questions and Answers
What effect does a low temperature have on metabolism in microorganisms?
What effect does a low temperature have on metabolism in microorganisms?
- Decreases production of unsaturated fatty acids
- Increases production of saturated fatty acids
- Inhibits all metabolic functions
- Produces more unsaturated and short-chain fatty acids (correct)
Which of the following can be considered a hurdle for microbial growth?
Which of the following can be considered a hurdle for microbial growth?
- Low pH (correct)
- High humidity
- High protein content
- Low light
Which type of microorganisms is associated with spoilage in seafood from warm waters?
Which type of microorganisms is associated with spoilage in seafood from warm waters?
- Lactobacillus spp.
- Salmonella spp.
- Micrococcus spp. (correct)
- Pseudomonas spp.
In the context of food spoilage, what action does pectinase perform?
In the context of food spoilage, what action does pectinase perform?
What characteristic does lactic acid bacteria have when found in unpasteurized milk?
What characteristic does lactic acid bacteria have when found in unpasteurized milk?
Which of the following microorganisms is primarily responsible for the sour odor in milk?
Which of the following microorganisms is primarily responsible for the sour odor in milk?
What is a primary source of microbial flora in food during handling?
What is a primary source of microbial flora in food during handling?
Which of the following is a characteristic of spoilage organisms in muscle foods?
Which of the following is a characteristic of spoilage organisms in muscle foods?
Which of the following statements accurately describes bacteria?
Which of the following statements accurately describes bacteria?
What is the optimal pH range for the growth of most bacteria?
What is the optimal pH range for the growth of most bacteria?
What factor most significantly affects the microbial growth of bacteria?
What factor most significantly affects the microbial growth of bacteria?
Which group of microorganisms can survive in very low pH environments?
Which group of microorganisms can survive in very low pH environments?
Which type of microorganism requires a specific low level of oxygen for growth?
Which type of microorganism requires a specific low level of oxygen for growth?
At what temperature range do psychrophiles thrive?
At what temperature range do psychrophiles thrive?
What is the primary consequence of low water activity for bacterial survival?
What is the primary consequence of low water activity for bacterial survival?
Which classification of bacteria survives best at temperatures around 30-37C?
Which classification of bacteria survives best at temperatures around 30-37C?
What compound is produced from lysine during protein degradation?
What compound is produced from lysine during protein degradation?
Which microorganism is utilized in the fermentation of yogurt?
Which microorganism is utilized in the fermentation of yogurt?
What is the primary end product of cereal grain fermentation during beer production?
What is the primary end product of cereal grain fermentation during beer production?
At what temperature and duration is whole milk heated during yogurt preparation?
At what temperature and duration is whole milk heated during yogurt preparation?
Which enzyme is added to milk to facilitate rennet coagulation in cheese making?
Which enzyme is added to milk to facilitate rennet coagulation in cheese making?
What role does pH play in the fermentation process mentioned in the content?
What role does pH play in the fermentation process mentioned in the content?
Which of the following statements about Clostridium laramie is true?
Which of the following statements about Clostridium laramie is true?
What happens to proteins when they are spoiled anaerobically by microorganisms like Pseudomonas and Acinetobacter?
What happens to proteins when they are spoiled anaerobically by microorganisms like Pseudomonas and Acinetobacter?
Flashcards
Microorganisms
Microorganisms
Small living things like bacteria, viruses, protozoa, and fungi that use organic matter to create inorganic compounds.
Bacteria
Bacteria
Single-celled organisms found everywhere. They can be different shapes (coccus, bacillus, spirillum) and have different responses to oxygen.
Water Activity (aw)
Water Activity (aw)
A measure of water availability for microbial growth, bacteria need higher aw than yeasts and molds
Factors affecting microbial growth
Factors affecting microbial growth
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Aerobes
Aerobes
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Mesophiles
Mesophiles
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Water Activity
Water Activity
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Temperature Class of Microbes
Temperature Class of Microbes
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Hurdle Concept
Hurdle Concept
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Sources of Microorganisms
Sources of Microorganisms
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Spoilage Microorganisms
Spoilage Microorganisms
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Pathogenic Microorganisms
Pathogenic Microorganisms
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Useful Microorganisms
Useful Microorganisms
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Muscle Food Contamination
Muscle Food Contamination
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Fruit and Vegetable Spoilage
Fruit and Vegetable Spoilage
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Dairy Microorganisms
Dairy Microorganisms
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Protein Spoilage
Protein Spoilage
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Cadaverine
Cadaverine
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Putrescine
Putrescine
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Milk Fermentation
Milk Fermentation
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Chymosin (Rennet)
Chymosin (Rennet)
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Yogurt Fermentation
Yogurt Fermentation
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Beer Fermentation
Beer Fermentation
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Lactic Acid Bacteria (LAB)
Lactic Acid Bacteria (LAB)
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Study Notes
Microorganisms
- Small living entities (bacteria, viruses, protozoa, fungi)
- Utilize organic matter to form inorganic compounds
- Eukaryotes (true nucleus) vs. prokaryotes (no true nucleus)
- Scientific names use genus and species names
- Example: Escherichia coli
Bacteria
- Unicellular organisms
- Size: 1 μm in length
- Ubiquitous (found everywhere)
- Classified by crystal violet retention (Gram-positive or Gram-negative)
- Different shapes (cocci, bacilli, spirilla)
- Sporulation: response to unfavorable conditions
Factors Affecting Microbial Growth
- Nutrients: Chemotrophic (lithotrophic or organotrophic) vs. phototrophic
- Water activity (aw): Measure of unbound water availability; bacteria require higher aw than other organisms (>0.9).
- Acidity/Alkalinity (pH): Optimal growth ranges vary by organism (e.g., bacteria 4.5-9.0, optimal 6.5-7.5; yeasts 3.0-8.5, optimal 4.0-6.5; molds 2.0-11.0, optimal 4.5-6.8)
Sources of Microorganisms
- Air, soil, water, surfaces
- Human colon
- Food: raw materials, handling, processing, storage
- Categorized as spoilage, pathogenic, or useful microorganisms
Muscle Foods (e.g. beef, pork, seafood)
- Microbial sources of spoilage
- Psychrotrophic aerobes
- Salmonella, Vibrio, and Aeromonas (pathogens in specific types)
Fruits and Vegetables
- Spoilage from acid-tolerant, or spore-forming microorganisms (e.g., Bacillus, Clostridium, Lactobacillus, Leuconostoc)
Dairy
- Lactic acid bacteria are important (found in unpasteurized milk)
- Pathogens like Mycobacterium, Coxiella, Listeria, Pseudomonas can cause problems during processing
Food Spoilage (Carbohydrates & Proteins)
- Carbohydrate spoilage: use of pectinase, cellulase, etc.
- Protein spoilage: breakdown to amino acids, foul-smelling compounds
Microbial Fermentation
- Milk fermentation (cheese, yogurt) uses bacteria and enzymes for different results
- Cereal grain fermentation (beer): uses yeast and enzymes to produce ethanol.
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Description
Test your knowledge about microorganisms, including bacteria, fungi, and viruses. This quiz covers their characteristics, classification, and the factors that affect their growth. Challenge yourself to identify different types and understand their ecological significance.
