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Basic-Microbiology1

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Amr Sadek
Amr Sadek

This document provides an overview of basic food microbiology. It discusses the characteristics of bacteria, including their shape, reproduction process, and growth curve phases. It also describes the differences between vegetative cells and spores. Several factors that influence microbial growth are outlined, including pH, moisture, oxygen conditions, nutrients, and temperature. Extrinsic factors like temperature, humidity, and other microorganisms are also noted. The document defines temperature controlled safety foods and provides examples. Finally, it briefly describes different types of foodborne illness.

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BASIC FOOD MICROBIOLOGY
Bacteria Microbiology • Microscopic • Single Cell • Shape – Cocci- Spherical* – Bacilli – Rod * – Sperilli – Corkscrew, Comma • *Most Food Borne Pathogens are Cocci or Rod shape
Bacterial Reproduction • Doubling • Binary Fission • 1 2 4 8 16 32 64 • Under optimal conditions most bacteria can double every 20 minutes.
Growth Curve Phases • Lag – Bacteria adapting to environment • Log – Logarithmic growth reproduce to high numbers in short period of time • Stationary – Death=Growth • Death – Sharp decline in numbers – Ran out of Nutrients – Accumulation of waste – Accumulation of toxin Objective - Extend the Lag Phase
Basic-Microbiology1
Spores vs Vegetative • Vegetative Cells – Living cells, metabolically active (ingest nutrients, secrete waste) • Spores – Endospore – Function – Protection from the environment – Dormant cell – no intake of nutrients, not secreting waste – Resistant to Heat, Cold, Chemicals, Radiation
What Microorganisms Need to Grow • Acronym – FAT TOM – F – Food – A – Acidity – T – Temperature – T – Time – O – Oxygen – M – Moisture
Intrinsic Factors • Intrinsic – pH – Moisture Content – Oxygen Needs – Nutrient Content – Antimicrobial Constituents – Biological Structures
pH • Effects of pH – Enzymes – Nutrients • Other Environmental Factors – Temperature – Salt – Age • No known pathogen grows below pH of 4.6 – Clostridium botulinum
Moisture • Remove and/or Bind Moisture – Humectants – Dehydration • Water Activity – Aw • Most Fresh Foods - Aw > 0.99 0 1 Pure waterNo water
Microbial Growth and Aw • Halophilic 0.75 • Xerophilic molds 0.61 • Osmophilic yeasts 0.61 • Lowest Aw for Pathogen Growth – 0.86 – Stapholococcus aureus
Oxygen Conditions • Aerobic – Requires air to grow and multiple • Anaerobic – Requires no air to grow and multiple • Microaerobic – Requires an atmosphere less than air • Facultative anaerobes – can live in the absence as well as in the presence of atmospheric oxygen
Others Factors • Nutrients – Fastidius vs non-fastidious – unusual and/or complex nutritional needs and must be grown on enriched media. • Biological Structure • Antimicrobial Factors – Naturally occurring factors
Extrinsic Factors • Temperature • Relative Humidity • Gases in the Environment • Presence of Other Microorganisms
Temperature • Microorganisms grow over a wide range of Temperatures • Psychrotrophs • Mesophiles • Thermophiles • Psychroduric • Thermoduric
Other Factors • Relative Humidity of Environment – Can change the Aw • Environmental Gasses – CO2, Ozone, modified atmosphere packaging
Temperature Control for Safety Foods (TCS) • High Moisture (H2O) – AW > 0.85 – AW – Water Activity – water available in a food for microbial growth and chemical reactions • pH > 4.6 • High Protein • High Starch
Examples TCS Foods • Milk/Milk Products • Shell Eggs • Meat: Beef, Pork, Lamb • Shellfish and Crustaceans • Fish • Baked Potatoes • Rice, beans, and vegetables • Poultry • Sliced Melons • Raw Sprouts and Sprout Seeds • Untreated garlic-and-oil mixtures
Types of Illness • Foodborne illness – Illness carried or transmitted to people by food. • Foodborne Infections – result of a person eating food containing pathogens, which then grow in the intestines and cause illness. – typically symptoms of foodborne illness do not appear immediately
Types of Illness • Foodborne intoxication – Result of a person eating food containing toxins (poisons) that cause an illness. The toxins my have been produced by pathogens found on the food or may be result of a chemical contamination, or part of the natural food. – Appear quickly, within a few hours.
Types of Illness • Foodborne Toxin-mediated infection – Result of a person eating food containing pathogens which then produce illness-causing – toxins in the intestines. • Gastrointestinal illness – Illness relating to the stomach or intestine
Questions

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Basic-Microbiology1

  • 2. Bacteria Microbiology • Microscopic • Single Cell • Shape – Cocci- Spherical* – Bacilli – Rod * – Sperilli – Corkscrew, Comma • *Most Food Borne Pathogens are Cocci or Rod shape
  • 3. Bacterial Reproduction • Doubling • Binary Fission • 1 2 4 8 16 32 64 • Under optimal conditions most bacteria can double every 20 minutes.
  • 4. Growth Curve Phases • Lag – Bacteria adapting to environment • Log – Logarithmic growth reproduce to high numbers in short period of time • Stationary – Death=Growth • Death – Sharp decline in numbers – Ran out of Nutrients – Accumulation of waste – Accumulation of toxin Objective - Extend the Lag Phase
  • 6. Spores vs Vegetative • Vegetative Cells – Living cells, metabolically active (ingest nutrients, secrete waste) • Spores – Endospore – Function – Protection from the environment – Dormant cell – no intake of nutrients, not secreting waste – Resistant to Heat, Cold, Chemicals, Radiation
  • 7. What Microorganisms Need to Grow • Acronym – FAT TOM – F – Food – A – Acidity – T – Temperature – T – Time – O – Oxygen – M – Moisture
  • 8. Intrinsic Factors • Intrinsic – pH – Moisture Content – Oxygen Needs – Nutrient Content – Antimicrobial Constituents – Biological Structures
  • 9. pH • Effects of pH – Enzymes – Nutrients • Other Environmental Factors – Temperature – Salt – Age • No known pathogen grows below pH of 4.6 – Clostridium botulinum
  • 10. Moisture • Remove and/or Bind Moisture – Humectants – Dehydration • Water Activity – Aw • Most Fresh Foods - Aw > 0.99 0 1 Pure waterNo water
  • 11. Microbial Growth and Aw • Halophilic 0.75 • Xerophilic molds 0.61 • Osmophilic yeasts 0.61 • Lowest Aw for Pathogen Growth – 0.86 – Stapholococcus aureus
  • 12. Oxygen Conditions • Aerobic – Requires air to grow and multiple • Anaerobic – Requires no air to grow and multiple • Microaerobic – Requires an atmosphere less than air • Facultative anaerobes – can live in the absence as well as in the presence of atmospheric oxygen
  • 13. Others Factors • Nutrients – Fastidius vs non-fastidious – unusual and/or complex nutritional needs and must be grown on enriched media. • Biological Structure • Antimicrobial Factors – Naturally occurring factors
  • 14. Extrinsic Factors • Temperature • Relative Humidity • Gases in the Environment • Presence of Other Microorganisms
  • 15. Temperature • Microorganisms grow over a wide range of Temperatures • Psychrotrophs • Mesophiles • Thermophiles • Psychroduric • Thermoduric
  • 16. Other Factors • Relative Humidity of Environment – Can change the Aw • Environmental Gasses – CO2, Ozone, modified atmosphere packaging
  • 17. Temperature Control for Safety Foods (TCS) • High Moisture (H2O) – AW > 0.85 – AW – Water Activity – water available in a food for microbial growth and chemical reactions • pH > 4.6 • High Protein • High Starch
  • 18. Examples TCS Foods • Milk/Milk Products • Shell Eggs • Meat: Beef, Pork, Lamb • Shellfish and Crustaceans • Fish • Baked Potatoes • Rice, beans, and vegetables • Poultry • Sliced Melons • Raw Sprouts and Sprout Seeds • Untreated garlic-and-oil mixtures
  • 19. Types of Illness • Foodborne illness – Illness carried or transmitted to people by food. • Foodborne Infections – result of a person eating food containing pathogens, which then grow in the intestines and cause illness. – typically symptoms of foodborne illness do not appear immediately
  • 20. Types of Illness • Foodborne intoxication – Result of a person eating food containing toxins (poisons) that cause an illness. The toxins my have been produced by pathogens found on the food or may be result of a chemical contamination, or part of the natural food. – Appear quickly, within a few hours.
  • 21. Types of Illness • Foodborne Toxin-mediated infection – Result of a person eating food containing pathogens which then produce illness-causing – toxins in the intestines. • Gastrointestinal illness – Illness relating to the stomach or intestine