1. APPLIED MICROBIOLOGY CHAPTER 26
Copyright © 2012 John Wiley & Sons, Inc. All rights reserved.

2. Microbes Found in Food 20% of E.R. visits are foodborne illness Grains
Claviceps purpurea mildew
Aspergillus
Rhizopus
Produce
Pseudomonas
Salmonella, Listeria on cantaloupes
Meats/Poultry
Salmonella, Clostridium, Staphylococcus
Helminths
Molds
© 2012 John Wiley & Sons, Inc. All rights reserved.

3. Microbes Found in Food (cont.)
Fish/Shellfish
Vibrio cholerae, V. parahemolyticus
Salmonella
Milk
Staphylococcus aureus (milk handling)
Pseudomonas
Mycobacterium bovis
© 2012 John Wiley & Sons, Inc. All rights reserved.

4. Preventing Disease and Food Spoilage
Canning
Commonest method
Moist heat under pressure
Balances flavor/safety
Thermophilic (flat sour) food spoilage
Bacillus stearothermophilus
Avoid temperature abuse to cans
Acid taste, no gas production
© 2012 John Wiley & Sons, Inc. All rights reserved.

5. Mesophilic Canned Spoilage
Mesophilic food spoilage
Improper cooking
Flaws in cans
Gas often seen
Botulism is a risk in canned meats
Home canners need to follow USDA guidelines
© 2012 John Wiley & Sons, Inc. All rights reserved.

6. Modern Food Preservation Methods
Refrigeration/ Freezing
Frig. – few days only – bacteriostatic
Freezing – also bacteriostatic
Softer textures due to ice crystals
May enhance thawed food spoilage
© 2012 John Wiley & Sons, Inc. All rights reserved.

7. Dessication Drying Removal of 90% or more of moisture
Microbes may not be killed
Osmotic control with salt/sugar adds bacteriocidal effects
© 2012 John Wiley & Sons, Inc. All rights reserved.

8. Food Preservation Methods
Irradiation
Safe but expensive
X-rays, γ-rays
Public education is needed
Chemical Preservatives
Organic acids
Ozone
Ethylene oxide for dried foods
© 2012 John Wiley & Sons, Inc. All rights reserved.

9. Pasteurization Destroys vegetative pathogens
High Temperature Short Time (HTST)
72oC, 15 secs
Low Temperature Long Time
70oC, 30 mins
Ultra High Temperature (UHT)
88oC, 3 secs
Refrigeration not needed
© 2012 John Wiley & Sons, Inc. All rights reserved.

10. Microbes as Food Fungi Yeast supplements Limited tolerance by humans
Algae
Chlorella
Shortened food chain
Some disease risks from sewage growth
Bacteria
Spirulina
65% protein
Origin S. America
© 2012 John Wiley & Sons, Inc. All rights reserved.

11. Microbes in Food Production
Baked goods
Bread
Saccharomyces cerevisiae
Carbon dioxide bubbles create leavening
© 2012 John Wiley & Sons, Inc. All rights reserved.

12. Cheese/Dairy Cheese Manufacture Add rennin to milk (curd)
Immature cheese – cottage cheese
Add Lactobacillus bacteria (anaerobic acid fermenters)
Allow ripening (aging) to decrease water, increase flavor
Classified by consistency
Very hard – Parmesan, Romano
Hard – Cheddar, Swiss
Semi-hard – Stilton, Danish Blue
Soft – Camembert, Brie
© 2012 John Wiley & Sons, Inc. All rights reserved.

13. Other Fermented Foods Vinegar Sauerkraut and pickles Green olives Poi
Soy products
Fermented meats
Yoghurt
© 2012 John Wiley & Sons, Inc. All rights reserved.

14. Fermented Beverages - Beer
Beer/Ales
Starch from rice, wheat, barley
Malting of grains,
Hop addition
Yeast Saccharomyces cerevisiae
Tank storage (lagering)
Alcohol is filtered, pasteurized (diluted)
© 2012 John Wiley & Sons, Inc. All rights reserved.

15. Fermented Beverages – Wine and Spirits
Monosaccharides from fruit juice
Yeast added after sulfites/pasteurization
Filtration, clarification, wood aging
Spirits
Alcoholic mash is “distilled” to boil off alcohol
Fruit or grains may be used
© 2012 John Wiley & Sons, Inc. All rights reserved.

16. Industrial and Pharmaceutical Biology
Valuable commodities
Acetone/ glycerol
Vitamins
Antibiotics, vaccines
Monoclonal Ab, human insulin (Humulin)
Metabolic Processes are modified for commercial production by
Altered nutrition/ environment
Citric acid from molds in iron free media
Altered gene regulation
Overproducers of penicillin
Recombinant genes
Humulin from bacteria
© 2012 John Wiley & Sons, Inc. All rights reserved.

17. Industrial Fermentation
Challenges
Toxicity to microbes
Extraction from cells
Aeration
Bioreactor Types
Continuous
pH, temperature, nutrient levels are maintained
© 2012 John Wiley & Sons, Inc. All rights reserved.

18. Additional Organic Products
Biofuels
Oils from algae
Ethanol
Thermophilic Clostridium species
Zymomonas
Ethanol from 5-carbon sugars
Other fungal species
Enzymes
Proteases, amylase, invertase
Amino acids (Essential)
© 2012 John Wiley & Sons, Inc. All rights reserved.

19. Useful Organic Products
© 2012 John Wiley & Sons, Inc. All rights reserved.