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Food safety
INTOXICATION VS INFECTION
Food Intoxication- toxins/ toxicants responsible
◦ Produced in foods as by-products of microorganisms, plants or animals
◦ Cause disease upon ingestion
Food Infection- multiplication of pathogenic Microorganisms responsible
◦ Viable microorganisms in the food at the time of consumption-> grow in the host- cause illness.
microorganisms
We can find them everywhere
Microorganisms cause a great deal of food spoilage throughout the world
This has major economic consequences and as well as loss of potential sources of nutrients,
since the food typically is discarded.
microorganisms
Examples of microorganisms:
◦ Bacteria, mold and yeast
◦ Viruses can be agents of food borne disease but
◦ VIRUSES DO NOT CAUSE FOOD SPOILAGE, NOR DO THEY PRODUCE FERMENTED FOODS
MICROORGANISMS
The Good--◦ Used in food processing (cheese, yogurt, olives)
The BAD--◦ Can cause food spoilage
◦ Food preservation, packaging and storage technology kills or delays metabolic activities of MO
The ugly--◦ MO that can cause foodborne disease
◦ Food processing, packaging and storage techniques are designed to kill these MO or prevent their
growth
Bacteria, yeast, molds
Bacteria- unicellular organism-1 micron or less in length
◦ Gram staining- classify bacteria based on whether the bacteria retain crystal violet in their cell
membrane
◦ Gram positive ( violet/blue)- thick cell wall, with no outer membrane
◦ Gram negative( pink) – thin cell wall and have an outer membrane
◦ Rods (long and narrow)
Bacteria, yeast, molds
Bacteria- fast growth
◦ Generation time fir 1 cell division cycle
◦ Eg) if 7 min,then in 3.5 hrs (210 min), one cell would multiply to 2 30= 1 billion cells!
◦ Vegetative cells (active) or spores (dormant)
◦ Cocci (circular shape) and rods (long and narrow)
Bacteria
Vegetative cells ( active) or spores ( dormant)
Cocci (circular shape) and rods (long and narrow)
Clostridium botulinum
Yeasts
Yeasts- slower growth but more toleratnt
◦ Tolerant lower pH or water activity
◦ Reproduced by budding
Molds
Molds- even more tolerant of low pH and water activity
Grow by network of hairlike fibres (mycelia)  spores
Spores
mycelia
Bacteria & mold Spores
Spores- dormant form
◦ Very resistent to various conditions
◦ Germinate under favorable conditions -> active vegetative cells
◦ Notorious example: clostridium botulinum
◦ Spores are very heat resistant
◦ Germinate-> Toxin-> Botulism (pathogenic)
◦ Spores do not change flavors
◦ Stomach acid will not allow spores to release
◦ BoTox- botulism toxin
Classification of microrganisms by
Oxygen and Temperature requirements
for growth
Oxygen requirements:
◦ Faculative anaerobe- in presence / absence of oxygen
◦ Bacteria, yeasts
◦ Small amount of oxygen ( not Mold)
◦ Mold may only grow on top in jar
◦ Anaerobic- only in the absence of oxygen
◦ Bacteria only
◦ Aerobic- only in presence of oxygen
◦ Bacteria, yeast, molds
Classification of microorganisms
temperature requirements
min
max
optimum
Psychrophiles
0-5
18
Psychrotrophs
0 to -5
30-35
21
cause food spoilage in frig (listeria—deli meats)
Mesophiles
10
45-50
35
pathogens- cause disease/ grow in danger zone
Thermophiles
50
80-100
65
spores of c.botulism
Spoilage of refrigerated foods- psychrotrophs
Many disease causing bacteria are mesophiles
10 o C
What contributes to microbial growth?
F= Food
F=Food (Carbohydrates, Proteins and Fats)
A= Acidity ( pH higher than 4.6)
T= Temperature ( outside danger zone 41o F to 135o F)
( keep hot foods hot, cold foods cold)
T= Time (longer exposure = greater MO growth)
O= oxygen (greater exposure faster MO growth)
M= Moisture (water activity)
Microorganisms and Foodborne Disease
Foodborne Illness Outbreaks | Food Safety News
FACTS
5200 PEOPLE DIE EVERY YEAR FROM FOODBORNE ILLNESS
76 million cases of foodborne disease occur each year in the US
◦ cdc
Foodborne disease etiology (causes)
Parasitic
◦ Cryptosporidium (water)
◦ Anisakiasis (fish)
◦ Acquired from consumption of infested food/ water
Plant
◦ amanita mushrooms, taro leaves, green potatoes, etc
Animal
◦ Poisonous animals
◦ Shellfish containing paralytic toxins, puffer fish, etc
Chemical
◦ Tin in corrosive metal cans, cleaning and sanitizing agents, etc
Microbiology= food/Waterborne Diseases (FBD)
Parasitic
◦ Cryptosporidium (water)
◦ Anisakiasis (fish)
◦ Acquired from consumption of infested food/ water
◦ Parasites such as Trichinella (pork)
Plant
amanita mushrooms, taro leaves, green potatoes,…
FBD example- solanine from green potatoes inhibit the action of enzyme ( cholinesterase) and
interfers with nerve transmissions and impulses
Potatoes cont.
Low levels (potato skin= 2.13mg/ 100g fresh weight)
“green” potatoes ( sunlight)-> 80-100 mg/ 100 g fresh weight
Solanine is insoluble in water
Lower the concentration by simply peeling potato
Not destroyed by heat ( cooking)
At 2-8 mg/kg baking weight humans display drowsiness, difficulty breathing, increased sensory sensitivity
Toxic ( LD50= 42mg/kg)
LD =lethal dose
But relatively low hazard /risk unless -> green potatoes
Animal
◦ Poisonous animals
◦ Shellfish containing paralytic toxins, puffer fish, etc
Seafood toxins
Saxitoxin- paralytic shellfish poisoning (psp)
◦ Neurotoxin in microscopic plankton (dinoflagellates)
May bloom under certain conditions (red tide)
◦ Found in shell fish ( muscles, clams, oysters)
◦ ‘filtering’ organisms- absorb toxins from water
and concentrate it in their tissues
◦ Both on east and west coasts of US
◦ Muscular and nerve paralysis
◦ Toxicity LD 5 mg/kg body wt (LD50 )
◦ Hazzard: know source of seafood, heed red tide signs
Chemical
◦ Tin in corrosive metal cans, cleaning and sanitizing agents, etc
Reasons why only some FBD are
reported?
Lack of reporting- Only 1-4 % are reported
Mistakenly diagnosed
◦ Mild cases blamed on 24 hour flu, a virus, overeating
Doctors fail to report to local health dept due to lack of evidence/ research available
Who is most at risk?
Very old
Very young
Immunocompromised
Expectant mothers ( pregnant)
Mold toxins (mycotoxins)produced by molds
Ergotism-(claviceps purpurea)= st Anthony’s fire
Rye and other cereal grains
Chemical ergot
Similar to LSD ( hallucinogens, insanity)
peanuts, corn, wheat, rice, cottonseed, nuts, milk, eggs, cheese
Highly toxic and potentially carcinogenic
Contains vaso constricting alkaloids (precursors for LSD 25)
Believed to be part of the salem witch hunt hysteria (1692)
◦ Mouldy rye bread … Science, 1976 v. 192
Mycotoxins- produced by molds
Aflatoxins (aspergilus flavus)
◦ Peanuts, corn, wheat, rice, cotton seed, nuts, milk, eggs, cheese
◦ Highly toxic and potently carcinogenic
◦
liver cancer
Examples of
food intoxication
Clostridium botulinum
E coli
Food infection
Salmonella
Listeria
Virus
Hepatitus a
norwalk
haccp
Factors in fbd
Prep food too far in advance and store improperly
Insufficient cooking/ reheating
Inadequate cooling
Cross contamination
**most pathogenic MO do not alter color, aroma, flavor, or texture of foods
Poster project
Choose one pathogen and create an illustrated poster with detailed information to present to the
class.
Include:
Scientific name
Picture or drawing of pathogen
Common name
Classification
Food sources
Symptoms/ results
Possible Prevention/ elimination methods or steps
Other information