Mod 4 B

• Project planning (Asynchronous)

  March 12
• Quiz 4 (Module 4)

  March 15
• Second LT (Modules 3 and 4)

  March 19
• Project Planning Output

  1. Title

  2. General Objective

  3. Objective 1

  4. Methods (general)

  5. Objective 2

  6. Methods (general)
• Submit to Canvas (March 12) – 10 points
• Intrinsic Parameters

  • pH
  • Moisture content
  • Oxidation–reduction potential
  • Nutrient
  • Antimicrobial constituents
  • Biological structures
• Antimicrobial Constituents are naturally occurring substances that possess and express antimicrobial activity
• Antimicrobial Constituents contribute to food stability
• Examples of Antimicrobial Constituents

  • Essential oils (e.g. Allicin in garlic)
  • Lactoferrin in cow’s milk – Iron-binding glycoprotein
  • Rotavirus inhibitor in raw milk – Destroyed by Pasteurization
  • Milk casein
  • Lysozyme in eggs and milk
• Biological Structures provide excellent protection against the entry and subsequent damage by spoilage organisms
• Examples of Biological Structures

  • Testa of seeds
  • Outer covering of fruits and nuts
  • Shell of eggs
  • Hide of animals
  • Scales of fish
• Storage Temperature is the most important extrinsic parameter that affects the spoilage of highly perishable foods
• Extrinsic Process Variables


  • Properties of the storage environment
  • Affect both the foods and their microorganisms
• Relative Humidity of the Storage Environment affects the water activity within the food and the ability of microbes to grow at the surfaces
• Gases in the Storage Environment influence the growth of microorganisms
• Examples of Gases in the Storage Environment

  • CO2 – Controls microorganisms in foods
  • O3 – Antimicrobial properties, Strong oxidizing agent (Makes lipid-rich food rancid)
• Presence and Activities of Other Microorganisms: Some foodborne organisms produce substances that are either inhibitory or lethal to others, e.g. antibiotics, bacter
• CO2


  • Controls microorganisms in foods
• O3


  • Antimicrobial properties
  • Strong oxidizing agent (Makes lipid-rich food rancid)
• Substances produced by some foodborne organisms

  • Antibiotics
  • Bacteriocins
  • Hydrogen peroxide
  • Organic acids
• Module 4: The Microbiota of Food Products

  1. Intrinsic Food Properties

  2. Extrinsic Process Variables

  3. Implicit Microbial Characteristics
• Implicit Microbial Characteristics

  1. Microbial interactions

  2. Beneficial or adverse effects
• Competition

  1. Limited energy and nutrient sources

  2. Competition outcome depends on the growth rate of competitors

  3. Fast-growing outcompetes slow-growing microorganisms

  4. Competitive exclusion
• Metabiotic

  1. Changes on food due to the metabolic activity of predominant microorganisms

  2. Succession of microorganisms

  3. Initial optimal growth of 1 or 2 types

  4. Creates an environment not optimal for their growth

  5. Changes favorable for other types of microorganisms
• Metabiotic


  • Ground meat in an air-tight bag with a little bit of air
  • Aerobes will grow first
  • Environment becomes anaerobic
  • Colonization of anaerobes
• Mutualism

  1. Two or more microorganisms help one another

  2. Metabolic by-products as a growth requirement
• Mutualism

  • Growth of Lactobacillus arabinosus (Phe) and Enterococcus faecalis (Folic acid) in minimal media
• Commensalism


  One microorganism benefits from the other microorganism
• Commensalism

  • Vinegar production
  • S. cerevisiae produces alcohol from sugar
  • Acetobacter aceti use ethanol to produce acetic acid
• Antagonism

  1. Microorganisms can adversely affect each other in growth environment

  2. One may kill the other

  3. Production of one or more antimicrobial components
• Antagonism

  • Nicin from L. lactis kills other Gram-positive bacteria and inhibits Gram-negative bacteria