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Assessment of Microbial Contaminants of Food and Their Remedies
Dr. Quratulain SyedPCSIR, Labs. Complex,Lahore
Objective
To Provide an overview of the
types of microorganisms involved in food
spoilage and food poisoning, their sources and control .
All Microbes Live in Environment
Microbes are minute living things that are usually unable to be viewed with the naked eye
Bacteria, fungi, protozoa, algae, and viruses are examples!
Food For All
What so ever is nutritionally good for us is equally good for microorganisms
Types of hazard in food
Food can be contaminated by:
• Chemical hazard
• Physical hazard
• Biological hazard
Chemical Contamination
Toxic substances ---- naturally or
added during the processing of food Cleaning solutions Food additives – nitrites, sulfites & MSG etc. Pesticides/insecticides – plant/fly sprays etc. Heavy metals – Cu, Cd, Pb, Zn, & brass Drugs – growth hormones, antibiotics Care must be taken ----------------to
prevent chemical contamination
Physical Contamination
Accidental introduction of any foreign objects
into foodSome examples are as follows•Dead insects• Hair• Jewelery• Glass• Pieces of metal• soil from the ground when harvesting;• a bolt from a processing plant when packaging;
Bacterial contamination
As soon as food is harvested or slaughtered or manufactured into a product ------- change. Main processes:
• Autolysis – self destruction--- caused by enzymes present in the food;
• Microbial spoilage – caused by the growth of bacteria, yeasts and moulds.
Natural Desirable Food Changes
• Autolysis and microbial changes are sometimes desirable (and are not referred to as spoilage)
• Enzymes cause fruits to ripen. • Fermented Foods Like
Bread, Yoghurt, cheese, pickle, Food acids etc.
Types of Bacteria
Pathogen – cause disease
Spoilers cause the quality of food to deteriorate
Beneficial used for food production of value added products.
Food Spoilage
Approximately 1/3rd of all food
manufactured in world is lost to
spoilage
Food spoilage –damage to the edible quality of foodSpoilage affects
Appearance
• taste
• texture
• odour Examples: sour milk, moldy cheese, slimy, rancid meat, discolored vegetables
Color change ---- in the spoilage
Black spots on meat ------- Cladosporium spp.
White spots------- Sporotrichum carnis.
Yellow or green spots ----------- Penicillium species.
A rainbow effect on fish---- Photobacteria ----enable raw fish to glow in the dark
Flavour Changes-----in spoilage
Sour /acid flavour/stale----Clostridium.Bitter flavour------ActinomyceteasBurnt/caramel flavour-----St.lactisSoapiness------PseudomonasTurnip like-----E.coliMalty flavour----P. florescenPotato like ----P.mocidoiensMusty flavour----ActinomyceteasAlcoholic -----yeast
Mould
• Common cause of food spoilage.• Some form toxins that can cause
illness.• Grow in a wide range of foods – high
acid, low moisture.• Freezing does not destroy.• Requires air to grow.
Food
Food
spoilage
Food contamination
Food Types
Support rapid growth & reproduction of infectious bacteria• High Risk: Cooked & ready-to-eat hot foods ,meat products mince, burger patties, roasts, stuffed
meats, seafood, poultry• Medium Risk: Uncooked & ready-to-eat: Sandwiches,
cheese• Low Risk: No further preparation – Peanut butter,
crackers, dry food
Biological hazards
The microorganisms us sick include
Viruses (rotavirus, norwalk virus….) Bacteria (Salmonella, E. coli, Listeria…) Parasites (Toxoplasma, Trichinella spiralis.) Mould (Aspergillus flavus….
BACTERIAL FOOD POISONING IS THE MOST COMMON ALL OVER THE WORLD AND CAN BE FATAL
Toxins
Some bacteria release poisons --- toxins which cause food poisoning.
Exotoxins: Remain in food once they have developed. Endotoxins: Toxins inside the human body only after
the food has been eaten
Toxins are not easily destroyed by cooking
Gram +ve. Gram -ve
Types of Food borne Illness
Infection Eating food contaminated with pathogens
Intoxication Eating food contaminated with the exo- toxin (poisons) formed by bacteria Eating food contaminated with other biological or
chemical toxins (poisons)Toxin-mediated infection Eating food contaminated with pathogens that
grow in the body and form toxins (poisons)
Food Poisoning Bacteria
• The multiplication of bacteria within the food plays an important part in causing diseases
• Usually need millions of bacteria to cause illness.
Conditions for bacterial growth
Micro-organisms need conditions to survive and reproduce these can include:
Temperature
Moisture
Food
Time
Oxygen
pH level
Water boils at 100ºC
Temperature of hot food is 82ºC
Danger zone for rapid growth of micro-organisms is 5ºC - 63ºC
Temperature of fridge is 1ºC - 4ºC
Freezing point of water is 0ºC
Temperature of freezer is -18ºC
Microorganisms Reproduce by binary fission dividing in two
This is what happens …………
Common Foodborne Bacteria
Salmonella Staphylococcus Aureus Clostridium Perfingens
Bacillus Cereus Found in soil, vegetation,
cereals and spices
Clostridium Botulinum Found in the soil and associated
with vegetables and meats
Salmonella
Sources – intestines of people and animals, animal food, raw meat, poultry, raw milk, raw eggs. infectious people after recovery becomes carrier –gall bladder. Raw milk may contain salmonellaCommon food vehicles –Low acid food, undercooked or cooked meat, raw milk and eggs.Incubation period – 6 to 72 hrs to produce endotoxin in intestine.Symptom – Abdominal pain, diarrhoea, vomit, feverSpecific characteristics. Multiplies from 5°C to 47°C under aerobic or anaerobic conditions. Survive freezing temp. destroyed by heat at 66°C
Control adequate refrigeration of food
Salmonella
On the basis of pathogencity three types of diseases• Salmonella septicemia• Enteric fever (typhoid)• Food poisoning Salmonella typhimorium Salmonella heidelburgIllness appear afetr 24 hrs of ingestionIllness depends on spp. No. of bacteria health status Children are more prone.
Clostridium botulinum
Clostridium botulinum
Sources – Fish, intestine, soil, and vegetables.raw milk
Common food vehicles – Low acid processed foodcontaminated after canning or vacuum packaging.
Incubation period – 2 hrs to 5 days. Heat resistantneurotoxin produced in foods.
Symptom – Difficulties in swallowing, talking andbreathing. Double vision and paralysis.
Characteristics – Spores and exotoxin will survive under normal cooking Temp.Bacteria multiply between 3.3°C and 48°C.vegataive cells detroy at 80 c and sporea st 120 C
Clostridium botulinum
Characters – heat resistance depends upon oxygen, acidity salt conc.pH = 7.0 spores resist boiling for many hourspH=3.5 spores killed in boiling condition for 10 minutesLow and medium canned /bottled food ,processed meat, fish. Vegetables Control suspected food must boil at 100 c for 15 minutes, gas and off odor food must reject . Don’t reheat food
E. coli has 150 serotypes. Most strains are harmless. 18 strains are pathogenic benificial strains are producing Vit K2 Serotype O157:H7 can cause serious food
poisoning in humans UIT infection Neonatal meningitis (E.coli contain antigen k1. IgM antibodis are primary antibodies and absent
from the mother and body recognizes antigen K1
E.coli
E. coli ability to survive for short periods outside the body makes them an ideal indicator organism to test
Most E. coli strains are harmless, but some, such as serotype O157:H7 can cause serious food poisoning in humans
E.coli
Escherichia coli O157:H7
Sources – Animal intestine, soil, and water.Common food vehicles – Undercooked or raw meat, vegetables, unpasteurized milk and apple juice and contaminated water.Incubation period – 2 to 5 days.Symptom – watery or bloody diarrhea, nausea, vomiting, cramps, fever.Characteristics – Hemolytic Uremic Syndrome (HUS).Acute kidney failure in childrenControl prevent cross contamination cooked and raw foodWashing of food
Staphylococcus aureus
Staphylococcus aureus
Sources – Human nose, mouth, skin, hands, spots, boils, septic cuts, etc. mastitis in animal Common food vehicles – Dairy products, cold cooked meat and poultry, etc.Incubation period – 1 to 7 hrs. Exotoxin produced in foods.Symptom – Abdominal pain, diarrhea, vomiting,subnormal temperature.Characteristics – bacterium is facultative anaerobe. Killed at pasteurized temp. Heat resistant toxin, salt tolerant– Toxin may survive boiling for up to 30 minutes. No foul order in food14 types of enterotoxin, toxin are resistant to photolytic enzymes so survive in stomachCooked food poultry milk cheese desserts barbecue
Bacillus cereus
Bacillus cereus
Sources – Dust and soil.
Common food vehicles – Cereals, corn flour, steamed rice, spices, etc. common in rice eating countries
Incubation period – 1 to 5 hrs. Exotoxin produced In foods. toxin is highly resistant to heat hemolytic and non hemolyticSymptom – Abdominal pain, diarrhea, vomiting,subnormal temperature.
Characteristics – Spores and exotoxin will survive under normal cooking Bacteria multiply between 7°C and 48°C.
Shigella
Shigellosis
Bacillary dysentery Most cases Shigella sonnei cases every year
Sources: Human fecal contamination of food, beverages, vegetables,
water Signs:
Watery or bloody diarrhea, nausea, vomiting, cramps, fever Onset: 2 days Duration: 5-7 days
Campylobacter
Campylobacteriosis
Campylobacter jejuniSources
Raw or undercooked poultry from feces Non-chlorinated water Raw milk mastitis Infected animal or human feces Poultry, cattle, puppies, kittens, pet birds
Clinical signs Diarrhea, abdominal cramps,
fever, nausea headache and muscle pain Duration: 2-5 days Control cross contamination
Campylobacteriosis
Chorionic diarrhoeaDysentery ------bloody diarrhoeaCholera-------dehydration diarrhoeaTyphoid fever---prolonged abdominal painOthers contaminants • Legionella pneumophila ---------upper respiratory
infection (resemble, flu/pneumonia)• Vibro cholerae---choler• Fungus--- Toxicosis---- mycotoxin Aflatoxins( M1 M2 G1 G2 B1 B2) Zeralenone ochratoxin ergotamine citrinin tricho-thecenes
Sources of Food Contamination
Food infection – caused by harmful live microorganisms that are present in food when consumed
Common Causes of Food Spoilage
12 % Food from unsafe sources 63% Improper STORAGE temp. 28% Poor personal hygiene 23% Contaminated equipment 21% Inadequate cooking 20% Other things
How are foodborne illnesses prevented?
Strategies to prevent food poisoning
Good personal hygiene Only allow healthy workers to handle food. Have all workers wash their hands and nails thoroughly with warm, running water and soap properly and frequently. Cover cuts and infections on hands.
Prevent cross-contamination
Store foods properly. Only use cleaned and sanitized utensils and surfaces for food preparation.
Keep the kitchen clean When cleaning plates and equipment, we need
to scrape and rinse off surface food
We need to do---
Wash fruit and vegetables to be eaten raw under running waterCook food immediately after defrosting. keep cooked food at 60°C or above until
served Cook or reheat packaged food strictly in
accordance with any directions on the label.
We need to do---
Thoroughly cook meat (145–165ºF), poultry (165ºF), and eggs (145ºF).
Cooked food should be reheated to 165ºF. Hot foods should be kept hot at 135ºF or
above.
Keeping cold food
We need to take cold groceries home to the refrigerator quickly as possible
Thaw frozen food in the refrigerator or Microwave
Refrigerate leftovers promptly. Separate large volumes of food so
they will cool more quickly. Keep purchased food chilled until
you get home from the store
Pest control and animals
Stop pests such as cockroaches and mice coming into the area where food is kept
Discourage pests by not leaving food or dirty dishes out on the benches
keep animals out of the kitchen.
Prevention of Food Poisoning WHO Ten Golden Rules
Food processed for safety Thoroughly cook Eat immediately Store carefully Reheat thoroughly No contact between raw & cooked Wash hands Keep food preparation surfaces clean Protect from pests Use potable water
Cooking high-risk foods thoroughly
Methods of Food Preservation - remove moisture
Dehydration: removing water under vacuum or by heating it (sun drying). Good for many foods, including vegetables.
Salting: adding salt not only sucks water out of food and microbes, but most organisms cannot live in a high salt environment. Good for fish & meats, changes the taste of the food.
Methods of Food Preservation - remove oxygen
Vacuum packing: get rid of oxygen by sucking it out under a vacuum. Good for many kinds of foods, and lasts as long as the vacuum is good.
Inert gas: storing food under an inert gas like nitrogen prevents many microbes from growing.
Methods of Food Preservation - cooling
Refrigeration or freezing: very common & easy, lasts as long as food stays frozen. Some microbes can survive freezer temperatures, so freezing should be used in combination with another method.
Methods of Food Preservation - heating
Cooking & boiling: one of most effect methods. Often changes taste of food, destroys or removes nutrients. Must be done long enough to ensure microbes are killed, but once done, you don’t have to keep heating.
Pasteurization: is the process of heating foods hot enough to kill bacteria, but not so long that you ruin the taste (e.g. milk & juice)
Methods of Food Preservation cont--
SterilizationKills virtually all microorganisms and their spores.Once food is batch-sterilized, or individually sterilized, must be stored in a hermetically sealed container, like a can, glass bottle, jar, or flexible plastic container.
Methods of Food Preservation - pickling
Pickling: not very common. Most microbes cannot live outside a certain pH range. Storing food in an acidic solution (contains salt & vinegar) kills bacteria, but can still be eaten. Pickling works by lowering the pH in the microbe’s environment
Chemicals Methods
Disinfection: use of chemicals (bleach) to kill microbes to control infectious diseases on surfaces where food is stored or prepared.
Applying insecticides: spraying chemicals onto crops has long been used to control microbes and insects. Chemicals are very effective, easy to apply, but can be harmful to the environment (plants, animals, humans).
Methods of Food Preservation - Irradiation
Irradiation is the deliberate process of exposing an item either packaged or in bulk, to certain types of radiation energy to bring about desirable changes.
Irradiation : Additional Tool for Improving Food Safety
Seriousness of the food safety issues and the lack of adequate
control measures to ensure 100% bacteria free food.
Does not and Can not Make Foods Radioactive It has the potential to significantly reduce both food
production losses and food born illness.
Irradiated foods need to be stored, handled and cooked in the same way as un-irradiated food.
Below 10 kGy there are no known toxicological, microbiological, or nutritional problems
Advantages
1. Reduce food borne disease
2. Reduce food spoilage
3. Reduce insect infestations
4. Prevent spouting/delay ripening
5. Reduce use of fumigants
6. Physical improvement
Irradiation Doses
Sterilize food products above 10 kGy
Pasteurize food 1-10 kGy Insect disinfestatin (less
than 1 kGy) Sprout inhibition in potatoes and
onions (less
than 0.5 kGy) Delay ripening of certain fruits (less than 0.3 kGy)
Changes in Food by Irradiation
Chemical changes
0.01% of the chemical bonds are affected
Biological effects
Biological function is changed by highly reactive hydrogen and hydroxl radicals
1. causes base damage, target DNA strands– broken down lose ability to reproduce.
Changes in Food by Irradiation
Changes in proteins:
▪ opening of peptide chains ▪ polymerization▪ coagulation ▪ precipitation
Enzymes:
Less sensitive to radiation. Complete inactivation requires abt. 5 times
the dose required to destroy microorganisms.
Changes in Food by Irradiation
Carbohydrates:
Depolymerization degradation
Vitamins: Are sensitive to radiation,
destruction similar to
heat process,
Lipids, natural antioxidants and pigments: are also sensitive
Effectiveness of the Process
Depends upon the amount of DNA in target organisms
Parasites and insect /pests large amounts of DNA rapidly killed at extremely low dose of irradiation.
Bacteria takes more irradiation to kill as they have less DNA.
Viruses resistant to irradiation at doses approved for foods
Effectiveness of the Process
Anaerobic conditions /freezing reduce the lethal effect of irradiation
Higher temperatures/oxygen conc. enhance the lethal effect of irradiation
Gram negative bacteria < Gram positive bacteria/molds/yeast < spores and viruses
Some microorganisms logarithmic phase are more susceptible to irradiation at low doses than during the stationary phase
Effect of Irradiation on Spoiled Food
Neither irradiation nor any other food treatment can
reverse the spoilage process
Organizations that Endorse Food Irradiation
World Health Organization
American Medical Association
Institute of Food Technologists
American Council on Science and Health
Food and Agriculture Organization
American Dietetic Association
Some of our hot selling food exports items are:MangoesCitrusApplesPeachesDry fruits and datesRiceVegetablesMedicine herbs and spices
condiments Wild edible mushroomsSeafood
Different Quarantine treatments
Chemical treatments Physical treatments
Fumigation Hot Water treatment
Methyl Bromide High temperature forced Air
Fumigation + Refrigeration of fruits
Vapors Heat
Cold treatment + Fumigation of fruits
Cold Treatment Radio Frequency heating
Control Atmosphere High Temperature
Quick Freeze
Treatments(CATTS) Ionizing Irradiation
MICROBIOLOGY TESTING LAB,PCSIR LABS COMPLEX, LAHORE
ISO-17025 Accredited Lab.NA &PNAC
Demonstrate that the lab. Operates a quality systemTechnically competent to carry
out specific task Able to generate technically
valid results that cold be interpreted globally
Formal and international recognition of the labs.
Facilitates bilateral and multilateral trade
SCOPE OF MICROBIOLOGY TESTING LAB. AT LLC
Water/Drinks testing (APHA)
Enumeration of Heterotrophic Plate
CountEnumeration of Total Coliforms
Enumeration of Fecal coliforms
Enumeration of E.coli
Enumeration of Pseudomonas spp.
FOOD MICROBIOLOGY TESTING
Enumeration of Total coliforms
Enumeration of Total Plate count
Enumeration of Fecal coliforms
Enumeration of E.coli Detection of
Salmonella Enumeration of
Staphylococci aureus Enumeration of Yeast Enumeration of Mould
Key actions for Important Food Issues Food Safety, Quality and Consumer Protection
ELEMENTS OF A NATIONAL FOOD CONTROL SYSTEM.
Food Law and Regulations Food Control Management Inspection Services Laboratory Services: Food Monitoring and
Epidemiological Data Information, Education, Communication
and Training