Food poisoning and
decomposition of meat and fat
Prepared by :
Dr. Chandra Bikram Kunwar
Food poisoning
Introduction
Food poisoning, or foodborne illness, related to
meat and meat products is a significant public
health concern due to the high nutrient content of
meat, which makes it an ideal medium for microbial
growth.
Food poisoning occurs when meat or meat products
contaminated with pathogenic microorganisms,
their toxins, or harmful chemicals are consumed.
Symptoms can range from mild gastrointestinal
discomfort to severe, life-threatening conditions
Causes of Food Poisoning Related to
Meat and Meat Products
A. Pathogenic Microorganisms:
1) Bacteria:
• Salmonella: Found in poultry, beef, and pork. Causes
salmonellosis, with symptoms appearing 6–72 hours after
consumption.
• Escherichia coli (e.g., E. coli O157:H7): Common in ground
beef and undercooked beef products. Can lead to
hemolytic uremic syndrome (HUS), causing kidney damage.
• Listeria monocytogenes: Found in processed meats (e.g.,
deli meats, hot dogs). Causes listeriosis, particularly
dangerous for pregnant women, newborns, and
immunocompromised individuals.
.
• Campylobacter jejuni: Prevalent in poultry. Causes
campylobacteriosis, a leading cause of bacterial
gastroenteritis
• Clostridium botulinum: Rare but severe, associated with
improperly canned or vacuum-packed meats. Produces
botulinum toxin, causing botulism (paralysis).
• Clostridium perfringens: Found in cooked meats held at
improper temperatures. Causes gastroenteritis with rapid
onset (6–24 hours).
• Staphylococcus aureus: Contaminates meat via improper
handling. Produces heat-stable toxins causing rapid-onset
vomiting
2) Viruses
Less common but include:
• Norovirus: Transmitted through contaminated
meat during handling or processing.
• Hepatitis A: Rare, linked to poor hygiene
during meat processing.
3. Parasites:
• Toxoplasma gondii: Found in undercooked pork, lamb, or
wild game. Causes toxoplasmosis, risky for pregnant
women and immunocompromised individuals.
• Trichinella spiralis: Associated with undercooked pork or
wild game (e.g., bear). Causes trichinellosis, with muscle
pain and fever.
• Taenia spp.: Tapeworms from undercooked Buffalo meat
(T. saginata) or pork (T. solium), causing taeniasis or
cysticercosis
4. Molds:
Rare, but some molds on cured meats produce mycotoxins,
which can cause illness if ingested in large amounts
B. Toxins:
• Bacterial toxins, such as those produced by
Staphylococcus aureus, Clostridium botulinum,
or Bacillus cereus, can remain in meat even
after cooking, as many are heat-stable.
• Toxins from spoilage processes (e.g., biogenic
amines like histamine in aged meats) may
cause mild poisoning symptoms.
C. Chemical Contamination:
• Pesticides, antibiotics, or hormones used in
animal farming can contaminate meat if not
properly managed.
• Heavy metals (e.g., lead, mercury) from
environmental exposure.
• Cleaning agents or packaging materials
contaminating meat during processing
D. Improper Handling and Storage:
• Meat is highly perishable, with a high water
activity (Aw) and neutral pH (5.5–6.5), ideal
for microbial growth.
• Storage
above
40°F
(4°C),
crosscontamination, or inadequate cooking allows
pathogens to proliferate.
Symptoms of Food Poisoning
• Symptoms vary by pathogen, toxin, or contaminant but typically
include:
• Common Symptoms:
– Nausea, vomiting, diarrhea (watery or bloody), abdominal cramps,
fever, and fatigue.
– Onset: Ranges from 1–6 hours (e.g., Staphylococcus aureus toxins) to
1–7 days (e.g., Salmonella, Listeria).
• Severe Symptoms:
– Dehydration (from prolonged vomiting/diarrhea).
– Neurological symptoms (e.g., blurred vision, paralysis in botulism).
– Kidney failure (e.g., E. coli-related HUS).
– Miscarriage or stillbirth (e.g., listeriosis or toxoplasmosis in pregnant
women).
– Chronic complications like reactive arthritis (Salmonella,
Campylobacter) or Guillain-Barré syndrome (Campylobacter).
• Duration: Most cases resolve in 1–7 days, but severe infections (e.g.,
listeriosis, botulism) may require hospitalization.
Risk Factors for Meat-Related Food
Poisoning
• Type of Meat:
– Poultry: High risk for Salmonella and Campylobacter due to natural gut
flora in birds.
– Ground meat: Susceptible to E. coli because grinding mixes surface
bacteria (where pathogens reside) throughout the product.
– Pork: Risk of Trichinella, Salmonella, and Toxoplasma.
– Processed Meats: Vulnerable to Listeria due to post-cooking
contamination during slicing or packaging.
– Game Meats: Higher risk of parasites (Toxoplasma, Trichinella) due to
less regulated processing.
• Preparation and Cooking:
– Undercooking (e.g., rare burgers or poultry) fails to kill pathogens.
– Cross-contamination from raw meat to ready-to-eat foods (e.g., via
cutting boards, knives).
– Reheating leftovers inadequately.
• Storage:
– Holding meat at 40–140°F (4–60°C), the "danger zone," promotes
pathogen growth.
– Prolonged storage, even in refrigeration, allows slow-growing
pathogens like Listeria to multiply.
• Processing and Supply Chain:
– Contamination during slaughter, butchering, or packaging.
– Poor hygiene in meat processing plants or retail settings.
– Improper canning or vacuum-packing, leading to anaerobic pathogen
growth (e.g., C. botulinum).
• Consumer Practices:
– Poor handwashing or kitchen hygiene.
– Ignoring "use-by" dates or consuming meat with off-odors or
sliminess.
Prevention of Food Poisoning from
Meat and Meat Products
• Safe Cooking:
– Use a food thermometer to ensure safe internal temperatures:
• Poultry: 165°F (74°C).
• Ground meats: 160°F (71°C).
• Whole cuts ( pork, lamb): 145°F (63°C) with a 3-minute rest.
• Processed meats (e.g., hot dogs): Reheat to 165°F (74°C).
– Avoid consuming raw or undercooked meat, especially poultry or
ground meat.
• Proper Storage:
– Refrigerate meat at or below 40°F (4°C). Freeze at 0°F (-18°C) for
long-term storage.
– Use fresh meat within 1–2 days (refrigerated) or freeze promptly.
– Store raw meat on the bottom shelf to prevent drips
contaminating other foods.
– Thaw meat in the refrigerator, cold water, or microwave—not at
room temperature.
• Hygiene and Handling:
– Wash hands, utensils, and surfaces thoroughly after handling raw meat.
– Use separate cutting boards for raw meat and ready-to-eat foods.
– Avoid rinsing raw poultry or meat, as it spreads bacteria via splashing.
• Processing and Purchase:
– Buy meat from reputable sources with proper refrigeration.
– Check "use-by" or "sell-by" dates and inspect for signs of spoilage (e.g., offodors, sliminess).
– Ensure processed meats are stored correctly and not consumed past
expiration.
• Special Considerations:
– Pregnant Women: Avoid deli meats unless reheated to 165°F (74°C) to
prevent listeriosis.
– Canned/Vacuum-Packed Meats: Discard bulging cans or packages with
unusual odors.
– Restaurants: Ensure meat is cooked to safe temperatures, especially burgers
or poultry.
•
•
Specific Considerations for Meat Types
Poultry:
– Highest risk for Salmonella and Campylobacter.
– Often contaminated during slaughter due to intestinal flora.
– Requires thorough cooking and strict hygiene to prevent cross-contamination.
•
Ground Meats:
– Greater surface area and mixing of surface bacteria increase E. coli and Salmonella risk.
– Must be cooked to 160°F (71°C) throughout, unlike whole cuts.
•
Processed Meats:
– Susceptible to Listeria due to post-cooking handling (e.g., slicing, packaging).
– Vacuum-packed or cured meats (e.g., sausages, bacon) risk C. botulinum if improperly stored.
•
Pork and Wild Game:
– Parasites (Trichinella, Toxoplasma) are a concern, especially in undercooked or improperly
processed meat.
– Freezing or thorough cooking eliminates parasitic risks.
•
Cured/Smoked Meats:
– May harbor Listeria or Staphylococcus if mishandled.
– Biogenic amines (e.g., histamine) in aged meats can cause mild poisoning symptoms.
Decomposition of Meat and Fat
• Introduction: Decomposition is the natural
process by which organic matter, such as meat
and fat, breaks down into simpler compounds
due to microbial activity, enzymatic processes,
and chemical reactions. This process renders
meat unsafe and unpalatable.
Mechanisms of Meat Decomposition
• Enzymatic Autolysis:
• Microbial Activity:
• Chemical Oxidation:
• Environmental Factors:
STAGES OF MEAT DECOMPOSITION
• Fresh: Meat is firm, moist, and has a mild odor.
Myoglobin gives it a bright red color (in beef).
• Early Spoilage: Surface sliminess, slight off-odor,
and color changes (e.g., dull red or brown).
Bacterial counts increase.
• Advanced Spoilage: Strong putrid odors, sticky or
slimy texture, discoloration (green, gray, or black
patches), and gas production in vacuum packs.
• Putrefaction: Complete breakdown with foul
smells (e.g., ammonia, sulfur), liquefied tissues,
and high pathogen risk.
Decomposition of Fat
• Fat in meat (intramuscular, subcutaneous, or
intermuscular)
undergoes
specific
decomposition
processes, primarily oxidative and hydrolytic rancidity.
• Oxidative Rancidity:
• Mechanism: Unsaturated fatty acids in meat fat react with
oxygen, forming peroxides and secondary breakdown
products like aldehydes and ketones. This is catalyzed by
heat, light, or metal ions (e.g., iron from blood)
• Effects: Produces rancid, "off" flavors (e.g., fishy, metallic,
or soapy tastes). Common in fatty meats like pork or
poultry.
• Factors: Accelerated by exposure to air, high temperatures,
and prolonged storage
• Hydrolytic Rancidity:
– Mechanism: Lipases (from meat or microbes)
break down triglycerides into free fatty acids,
glycerol, and other compounds. This is more
common in high-fat meats or processed products
like sausages.
– Effects: Results in sour or bitter flavors. Free fatty
acids may further oxidize, compounding offflavors.
• Factors: High moisture and microbial activity
promote lipase activity
• Microbial Degradation:
 Certain bacteria and molds metabolize fats, producing
volatile compounds that contribute to rancid odors.
 In anaerobic conditions, fats may ferment, producing
acidic or cheesy smells.
• Consequences of Fat Decomposition:
 Loss of palatability due to rancid flavors and odors.
 Reduced shelf life of meat products.
 Potential formation of toxic compounds (e.g., lipid
peroxides) in extreme cases.
• Stages of Fat Decomposition
• Fresh Fat:
– White or creamy, neutral odor, and firm texture.
– Minimal oxidation or hydrolysis due to low microbial/enzymatic activity.
• Early Rancidity:
– Slight yellowing or off-odor (e.g., faint stale or oily smell).
– Peroxide formation begins, detectable only by chemical analysis or sensitive
tasters.
• Advanced Rancidity:
– Pronounced rancid, fishy, or soapy odors and flavors.
– Visible discoloration (yellow or brown fat) and soft, greasy texture.
– High levels of free fatty acids and oxidative byproducts.
• Severe Degradation:
– Overwhelmingly rancid, acrid, or putrid smells.
• Fat becomes sticky, discolored, and inedible, with potential microbial
overgrowth
• Environmental Factors Influencing Fat Decomposition
• Oxygen Exposure:
– Aerobic conditions accelerate oxidative rancidity. Vacuum packaging reduces
oxygen but may promote hydrolytic rancidity in high-moisture meats.
• Temperature:
– Higher temperatures increase oxidation and lipase activity. Freezing slows
both processes significantly.
• Light:
– UV light catalyzes oxidation, especially in exposed fat (e.g., in display cases).
• Moisture:
– High moisture enhances hydrolytic rancidity by supporting lipase activity and
microbial growth.
• Fat Composition:
– Meats with more unsaturated fats (e.g., pork, poultry) are more prone to
oxidative rancidity than those with saturated fats (e.g., Buffalo meat).
Prevention of Decomposition
•
Refrigeration (32–40°F/0–4°C): Slows microbial growth, enzymatic activity,
and oxidation. Use within 1–2 days for fresh meat.
• Freezing (0°F/-18°C): Halts decomposition. Store for 6–12 months (beef) or 3–
6 months (pork, poultry) for best quality.
• Rapid Cooling: Chill meat immediately after slaughter to reduce initial
microbial growth.
• Packaging:
– Vacuum Packaging: Removes oxygen, inhibiting aerobic bacteria
(Pseudomonas) and oxidative rancidity. However, monitor for anaerobic
spoilers (Clostridium).
– Modified Atmosphere Packaging (MAP): Uses gas mixtures (e.g., CO₂, N₂) to
suppress microbial growth.
– Opaque Packaging: Shields fat from light-induced oxidation.
• Hygiene and Processing:
– Minimize contamination during slaughter, butchering, and processing by
maintaining sterile equipment and environments.
– Remove excess surface moisture to reduce microbial growth.
• Antioxidants:
– Add natural (e.g., vitamin E, rosemary extract) or synthetic antioxidants (e.g.,
BHA, BHT) to inhibit fat oxidation.
– Common in processed meats like sausages.
• pH Control:
– Lower pH (e.g., through fermentation in cured meats) inhibits spoilage
microbes.
• Drying and Curing:
– Reduce water activity through drying (e.g., jerky) or curing (e.g., salami) to
prevent microbial growth.
– Salt and nitrites in cured meats inhibit spoilers and pathogens.
• Consumer Practices:
– Store meat on the bottom fridge shelf to prevent drips.
– Check for spoilage signs (odor, texture, color) before cooking.
– Avoid prolonged storage or temperature abuse (e.g., leaving meat at room
temperature).