Food Microbiology

1
Milk and Dairy Products

• Food Microbiology

2
Modern Dairy Processing

• Pasteurization
• Fermentation
• Dehydration
• Refrigeration
• Freezing
• Wide Variety of Products

3
Milk as Growth Media

• Carbon and Nitrogen Sources
• Minerals and Micronutrients
• Growth Inhibitors
• 2SCN- H2O2 2H (SCN)2 H20
• (SCN)2 H2O HOSCN SCN-
  H
• HOSCN H OSCN-
• SCN- H2O2 OSCN- H2O

1
Lactoperoxidase
2
Lactoperoxidase
4
Dairy Products

• VERY Different from Fluid Milk
• Nutrients Removed/Concentrated
• Different Aw
• Different pH

5
Spoilage Organisms

• Psychrotrophs
• 3-7 C storage
• Proteolytic and lipolytic
• Sources
• Spoilage Rates
• Pasteurization Kills all Pathogens, not
  necessarily all spoilage
• Recontamination can occur from equipment
• Spoilage occurs at 106 to 107

6
Spoilage-Psychrotrophs

• Off-Flavors and Odors
• Texture and Appearance Changes
• Protein
• Bitter and Putrid Flavors
• Coagulation
• Fat
• Rancid and Fruity Flavors

7
Fermentative Spoilage

• Lactic Acid Bacteria
• Lactobacillus
• Lactococcus
• Leuconostoc
• Enterococus
• Pediococcus
• Streptococcus
• Coliforms
• LAB Usually out compete

8
Control

• Prevent Contamination
• Rapid Cooling
• Refrigeration
• Cleaning and Sanitizing
• Pasteurization
• Prevent Recontamination of Pasteurized Products

9
Fruits, Vegetables and Grains
10
Spoilage of Plant Materials

• Three Types
• Active Spoilage
• Passive/Wound Induced
• Passive/Plant Pathogen
• Induced
• Manifestations

11
Internal Defense Mechanisms

• Epidermal Layer
• Internal Tissues
• Lamella
• Primary Cell Wall
• Secondary Cell Wall
• Physiological State
• Microbial Enzymes

12
Vegetable Spoilage

• Natural Flora
• Bacteria, Yeast and Molds
• Post-Harvest Spoilage
• Land Use
• Water Sources
• Processing
• Short-term Preservation
• Long-Term Preservation

13
Fruit Spoilage

• Natural Flora
• Both Bacteria and Fungi
• Processing
• Washing
• Cutting
• Drying
• Fruit Concentrates
• Canning and Freezing
• Fruit Juices

14
Grain Spoilage

• Differ from Fruits and Vegetables
• Low Aw
• Natural Flora
• Bacteria still out-populate molds
• Molds Field Spoilage
• Processing
• Spoilage