Meat Microbiology

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Meat Microbiology

• Why study meat microbiology?
• Food Borne Diseases
• Food Spoilage
• Meat Quality
• Preservation
• Flavor Alteration

Remember -- deep animal tissue is sterile. The
main area of concern is any tissue near the
surface of a carcass and whole muscle cuts.
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Why is Meat is an Ideal Medium?

• High in moisture
• 70 water
• Rich in protein (nitrogenous food)
• 18 20 protein
• Minerals necessary for growth
• Sufficient carbohydrates
• Favorable pH (5.6)

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Sources of Contamination

• Slaughter (Animal)
• Equipment
• Air
• Humans

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Microorganisms of Concern

• Cooked product should be bacteria free.
• Cooking kills 99 of the bacteria.
• Three types of microorganisms of concern in meat
• 1. Bacteria
• Goodteria
• Badteria
• 2. Yeast
• 3. Molds
• toxins

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Bacteria Reproduction

• Via binary fission--splitting into equal parts

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Bacteria Reproduction
If a bacterias generation time is 3
minutes, in one hour 1 bacteria cell will become
one million (106). Spoilage occurs at 107.
Stationary
Log
Number
Death
Lag
Time
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Factors that affect microbial growth

• 1. Temperature -- bacteria grow at temperatures
  from 32 to 150F. However, no single bacteria
  will grow over this entire range. Therefore,
  they are classified according to the range of
  temperature at which they grow best.

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Factors that affect microbial growthTemperature
contd

• A combined temperature-time value must be reached
  to kill a microorganism with heat. Attaining a
  certain temperature to kill the organism is not
  enough. It must be held at a given temperature
  long enough to kill it.

• Temperature abuse is the primary reason for meat
  spoilage. Therefore, never hold meat between 40
  and 140F.

LIFE BEGINS _at_ 40
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Temperatures Effect on Bacteria Growth

• For every 10oF increase in storage temperature
  there is a doubling in growth rate
• For every 10oF decrease in storage temperature
  growth rate is cut in half.

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Factors that affect microbial growth

• 2. Moisture -- the water requirement for
  microbial growth is defined in terms of water
  activity (aw) of the medium.
• Fresh meat has an aw of 0.99 or higher
• The aw minimum for bacteria to grow is 0.90
• aw reduction is a means of food preservation
• drying
• salting
• freezing

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Factors that affect microbial growth

• 3. Oxygen availability --
• Aerobic -- oxygen must be present to grow
• Aerobic psychrophiles are the most
  common meat spoiler.
• Anaerobic -- cannot grow when oxygen is
  present
• Facultative -- growth occurs both in the
  presence or absence of oxygen

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Factors that affect microbial growth

• 4. pH (acidity) --
• pH of 6.5 is normal for bacteria growth
• pH range for most pathogens to grow in is 4.8
  to 7.0

5. Physical properties -- Surface area -- the
more surface area (large area exposed to oxygen)
the more microbial growth Curing
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Review of Growth Factors

• 1. Temperature
• 2. Moisture
• 3. Oxygen Availability
• 4. Acidity
• 5. Physical properties

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REVIEW

• PSYCHROPHILES
• MESOPHILES
• THERMOPHILES
• NEVER KEEP MEAT BETWEEN?
• BACTERIA ARE EVERY WHERE

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Foodborne Illness

• FBI

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Organisms of Concern

• Consumed microorganisms (foodborne
  microorganisms) may cause health problems either
  by intoxication or infection.
• Intoxication -- microbes produces a toxin, which
  when ingested by the host (human), triggers
  sickness
• Infection -- organism is ingested by the host,
  then grows and by its presence it disrupts the
  normal functioning of the system
• Enterotoxins -- Organism grows in the GI tract
  and produces toxins

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WHO ARE AT RISK?

• YOUNG CHILDREN
• Immune system kicks in after 1 yr.
• ELDERLY
• IMMUNOCOMPROMISED
• CANCER AIDS
• PREGNANCY
• 20 SUPRESSION IN IMMUNE SYSTEM

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Incubation Period

• lt 1 hour usually chemical poisoning or
  alergic reaction
• 1 7 hours indicates preformed toxin
• 8 14 hours probable C. perfringens
• gt 14 hours other infectious or enterotoxins
• Can be up to 21 days.

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FBI -- Potential Regulatory Activity
CONTAMINATION OCCURS
REGULATORY ACTIVITY
USDA
Producer
2
FDA
Manufacture
5
STATE
43
HRI
CITY
50
Consumer
MOM
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Organisms of Concern

• Salmonella (infection)
• Source animals or animal products
• Poultry (100) and Swine
• spread by direct contact with contaminated people
  or animals, and by handling during the
  manufacture and transportation of food and food
  ingredients
• killed by pasteurization
• 161 F for 15 sec, 143 F for 30 minutes
• key avoid cross-contamination of cooked product
  with raw product

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SALMONELLA CONT.

• 800,000 TO 4 Million cases per year
• 500 Deaths per year
• lt1 up to 10 elderly
• Symptoms
• Nausea, Vomiting, Abdominal cramps, Diarrhea,
  Fever, Headache
• On Set 6 To 72 Hours
• Infective Dose As Few As 15-20 Cells
• Last 4-7 days

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Escherichia coli

• E. coli is one of the most wide spread organisms
  in nature
• Most strands are goodteria
• E. coli 0157H7 enterotoxin
• contamination occurs usually via improper
  slaughter procedures or improper and unsanitary
  handling of cooked product
• Produces a potent toxin that cause sever damage
  to the lining of the intestine other damage

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E Coli O157H 7 cont.

• Symptoms
• Severe cramping, watery diarrhea which becomes
  grossly bloody occasionally vomiting, low grade
  fever last 8 days
• Very young hemolytic uremic syndrome renal
  failure
• As few as 10 organism
• Associated with undercooked hamburger,
• un-pasteurized fruit juices, dry-cured salami,
  lettuce, game meat, cheese, raw milk
• Mortality rate in elderly as high as 50

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E Coli 0157H7

• Jack in the Box
• Hudson Foods
• Spinach
• Taco Bell
• Topps
• Food Recalls

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Campylobactor jejuni (infection)

• Leading cause of bacterial diarrheal illness in
  U.S.
• Not carried by healthy individuals but is
  isolated from healthy cattle, chickens, birds and
  flies.
• will not grow at temperatures less than 86 F,
  yet is destroyed by pasteurization
• key avoid cross-contamination of cooked product
  with raw product

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Campy cont.

• Associated Foods
• Raw chicken
• 20 to 100 of retail chicken contaminated
• Raw milk
• Bacteria carried by flies
• Non chlorinated water
• Up to 4 million cases/year
• 1 death/1,000 cases
• Children under 5 and young adults most frequently
  afflicted

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Listeria monocytogenes (infection)

• Listeria is everywhere -- in soil, vegetation,
  all types of animals and water
• Cold/Heat/Drying resistant
• Does not form spores
• Key avoid post-cooking contamination
• Big concern in ready to eat (RTE) products
• Lunch meats, Hot Dogs, etc.

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Listeria cont.

• Associated foods
• Raw milk
• Cheeses (soft-ripened varieties)
• Ice cream
• Raw vegetables
• Fermented raw meat sausages
• Raw and cooked poultry
• Raw meats
• Raw and smoked fish

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Clostridium botulinum

• (anaerobic, intoxication)
• Potent, Heat labile Neurotoxin
• A few nanograms of toxin can cause illness
• 180F for 10 minutes
• Spores are heat resistant
• High mortality rate
• Associated with inadequately processed home
  canned food
• Widely distributed in nature

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Clostridium botulinum

• Associated foods
• Low acid canned foods
• Sausages
• Meat products
• Canned vegetables
• Seafood
• Almost any type of food that is not very acidic
  (pH gt 4.6) can support growth and toxin production

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Trichinella spirillis

• (not a bacteria)
• Microscopic parasite
• muscles of rats, dogs, cats, swine,horses, wild
  game, humans
• Humans acquire by eating improperly prepared
  meats of infected animals
• Dosage of concern about 1,000 larvae
• 2 death rate

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Trichina

• Occurrence in commercial swine lt1
• 1940s 400 cases/yr ---- 1994 32/yr
• Garbage feeding
• Home freezer
• Cooking
• Cases associated with eating game increasing
• Bear, wild boar, walrus, cougar

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Trichina

• Control
• Cook to internal temperature of 144F
• Margin of safety 160F
• Curing such as for ham and some sausages
• Freezing retail cuts
• 5F 20 days
• -10F 10 days
• -20F 6 days
• Irradiation FDA approved

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REMEMBER

• KEEP IT
• COLD
• CLEAN
• DRY
• MOVING
• and COOK IT!