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, lifethreatening conditions
Causes of Food Poisoning Related to Meat and Meat
Products
A. Pathogenic Microorganisms:
1) Bacteria:
 Salmonella: Found in poultry, Carabeef, and pork. Causes salmonellosis, with
symptoms appearing 6–72 hours after consumption.
 Escherichia coli (e.g., E. coli O157:H7): Common in ground meat and
undercooked meat 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.
.
Causes of Food Poisoning continued..
 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
Causes of Food Poisoning continued..
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.
Causes of Food Poisoning continued..
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
Causes of Food Poisoning continued..
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.
Causes of Food Poisoning continued..
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
Causes of Food Poisoning continued..
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), cross-contamination, 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.
 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 fails to kill pathogens.
 Cross-contamination from raw meat to ready-to-eat foods (e.g., via cutting boards,
knives).
 Reheating leftovers inadequately.
Risk Factors………..
 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:
 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., off-odors,
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 crosscontamination.
 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:
 Immediately after slaughter, endogenous enzymes (e.g.,
proteases, lipases) begin breaking down proteins and
fats. This is initially beneficial, as it tenderizes meat
during aging.
 Over
time, unchecked autolysis leads to tissue
breakdown, producing a soft, mushy texture and offflavors.
Mechanisms of Meat Decomposition
 Microbial Activity:
 Bacteria:
Spoilage bacteria like Pseudomonas and Brochothrix
proliferate in aerobic conditions, while Clostridium and
Lactobacillus dominate in anaerobic environments (e.g., vacuumpacked meat).
 Yeasts and Molds: These grow on meat surfaces, especially in
high-humidity environments, causing sliminess or fuzzy growth.
 Microbial metabolism produces byproducts like ammonia, hydrogen
sulfide, and organic acids, leading to foul odors (e.g., "rotten egg"
smell) and discoloration (e.g., green or gray hues).
Mechanisms of Meat Decomposition
 Chemical Oxidation:
 Oxygen
exposure causes oxidative rancidity in meat,
particularly in fats. This results in off-flavors described as
"cardboard-like" or "stale."
 Myoglobin, the protein responsible for meat’s red color,
oxidizes to metmyoglobin, turning meat brown or gray.
Mechanisms of Meat Decomposition
 Environmental Factors:
 Temperature: Decomposition accelerates above 40°F/4°C,
with optimal microbial growth at 77–104°F (25–40°C).
 Moisture: High water activity in meat supports microbial
growth.
 Oxygen: Aerobic bacteria thrive in oxygen-rich environments,
while anaerobic bacteria dominate in low-oxygen settings.
 pH: Fresh meat has a pH of 5.5–6.5, ideal for most spoilage
microbes. As decomposition progresses, pH may rise due to
ammonia production.
STAGES OF MEAT DECOMPOSITION
 Fresh: Meat is firm, moist, and has a mild odor.
 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 off-flavors.
 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.
Prevention of Decomposition cont……
 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.
Prevention of Decomposition cont……
 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).
THANK YOU!