1. Extrinsic factors
1.1. • Temperature • Key Terms: Refrigeration (1-4°C), high temperatures, psychrotrophs (e.g., Pseudomonas), mesophiles (e.g., Listeria monocytogenes) • Connections: • Slows Microbial Activity: Refrigeration inhibits psychrotrophic bacteria, essential for spoilage management. • Pasteurization and UHT: Reduces
1.2. Relative Humidity (RH) • Key Terms: Moisture control, condensation, packaging stability • Connections: • Surface Microbial Activity: High RH increases surface moisture, promoting microbial growth. • Packaging Stability: Controlled RH prevents contamination, maintaining packaging integrity.
2. Implicit factors
2.1. Microbial Interactions
2.1.1. • Key Terms: Competition, antagonism, mutualism
2.1.2. • Connections:
2.1.3. • Shapes Microbial Ecology: Balances microbial populations within milk.
2.1.4. • Influences Spoilage and Preservation: Microbial relationships impact spoilage rates and fermentation processes.
2.1.5. • Inhibitory Substances
2.1.6. • Key Terms: Bacteriocins, lactic acid, organic acids
2.1.7. • Connections:
2.1.8. • Suppresses Pathogens and Spoilage Organisms: Bacteriocins and acids contribute to microbial stability by reducing spoilage risks.
2.1.9. • Produced by Specific Microbes: Lactobacillus produces lactic acid, influencing microbial communities.
3. Relative Humidity (RH) • Key Terms: Moisture control, condensation, packaging stability • Connections: • Surface Microbial Activity: High RH increases surface moisture, promoting microbial growth. • Packaging Stability: Controlled RH prevents contamination, maintaining packaging integrity.
4. Intrinsic factors
5. • Nutrient Content
5.1. Key Terms: Proteins (casein, whey), lactose, fats, vitamins and minerals
5.1.1. • Connections:
5.1.2. • Energy Source for Microbes: Nutrients like lactose feed microbes (Lactobacillus, Streptococcus), while proteins and fats support Pseudomonas.
5.1.3. • Degradation by Spoilage Organisms: Nutrient breakdown by spoilage organisms affects sensory qualities.
5.1.4. • Outcome: Nutrient richness supports diverse microbial communities.
6. • Natural Antimicrobial Components
6.1. Lactoferrin, lactoperoxidase, immunoglobulins, iron-binding, reactive molecules
6.2. • Connections:
6.3. • Inhibits Spoilage and Pathogens: Iron-binding and oxidative mechanisms inhibit E. coli and Listeria.
6.4. • Natural Defense Layer: Adds protection against microbial contamination.
6.5. • Outcome: Enhances stability under controlled storage.
7. Intrinsic
8. • Water Activity (Aw)
8.1. High water content, Aw ~0.98, psychrotrophic microorganisms
8.2. e Pseudomonas.
9. • pH and Buffering Capacity
9.1. Slightly acidic to near-neutral (pH 6.5-6.7), casein, lactate fermentation
9.1.1. • Connections:
9.1.2. • Supports Microbial Growth: Connects to Lactobacillus and Streptococcus through lactose fermentation.
9.1.3. • Stabilizes pH Changes: Buffering helps maintain milk stability, influencing curdling and acidity shifts.
9.1.4. • Outcome: pH shifts with microbial growth, impacting curdling and acidity.
9.1.5. • Redox Potential (Eh)
10. • Redox Potential (Eh)
10.1. Oxidative-reductive balance, positive Eh (fresh milk), anaerobes vs. aerobes
10.1.1. • Connections:
10.1.2. • Aerobic vs. Anaerobic Growth: Positive Eh supports aerobic growth (e.g., Pseudomonas), while negative Eh favors anaerobes like Clostridium.
10.1.3. • Storage Impact: Vacuum packaging or low oxygen decreases Eh, affecting microbial populations.
10.1.4. • Outcome: Storage environment impacts microbial dominance.