APPLIED MICROBIOLOGY

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APPLIED MICROBIOLOGY

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Microbes Found in Food
20% of E.R. visits are foodborne illness
Grains
–Claviceps purpurea mildew
–Aspergillus
–Rhizopus
Produce
–Pseudomonas
–Salmonella on cantaloupes
Meats/Poultry
–Salmonella, Clostridium, Staphylococcus
–Helminths
–Molds

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Microbes Found in Food (cont.)
Fish/Shellfish
–Vibrio cholerae, V. parahemolyticus
–Salmonella
Milk
–Staphylococcus aureus (milk handling)
–Pseudomonas
–Mycobacterium bovis

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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

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Canning
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

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Food preservation (cont.)
Refrigeration/ Freezing
–Frig. – few days only – bacteriostatic
–Freezing – also bacteriostatic
•Softer textures due to ice crystals
•May enhance thawed food spoilage
Drying
–Removal of 90% or more of moisture
–Microbes may not be killed
–Osmotic control with salt/sugar adds
bacteriocidal effects

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Preventing Disease and Food Spoilage
Irradiation
–Safe but expensive
–X-rays, γ-rays
–Public education is
needed
Chemical Preservatives
–Organic acids
–Ozone
–Ethylene oxide for dried
foods

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Pasteurization
Destroys vegetative pathogens
High Temperature Short Time (HTST)
–72
o
C, 15 secs
Low Temperature Long Time
– 70
o
C, 30 mins
Ultra High Temperature (UHT)
–88
o
C, 3 secs
–Refrigeration not needed

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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
–South America

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Microbes in Food Production
Bread
–Saccharomyces
cerevisiae
–Carbon dioxide
bubbles create
leavening

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Cheese manufacture
Add rennin to milk (curd)
Add Lactobacillus bacteria
(anaerobic acid fermenters)
–Immature cheese – cottage
cheese
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

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Cheese production
Dairy/Cheese

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Alcoholic Beverages — Beer
Beer/Ales
–Starch from rice,
wheat, barley
–Malting of grains,
–Hop addition
–Yeast
Saccharomyces
cerevisiae
–Alcohol is filtered,
pasteurized (diluted)

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Alcoholic Beverages — Wine
Wine
–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

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Industrial Fermentation
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

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Industrial and Pharmaceutical
Microbiology
Challenges
–Toxicity to microbes
–Extraction from cells
–Aeration
Reactor Types
–Continuous
–pH, temperature,
nutrient levels are
maintained