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Food - Unit 06 Summary.docx

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University of Guelph
Food Science
FOOD 2010
Massimo Marcone

UNIT 06: FOOD SAFETY CHAPTER 11 (Pgs 303-326) Foodborne illness: any illness resulting from ingestion of food  If agent causing disease is detected in sample of food victim has eaten  If there is cluster of cases among people who have nothing in common except food they ate  If intestinal tract is affect  If symptoms are like foodborne illnesses Biological hazards: bacteria, molds, viruses, parasites (protozoa, flatworms, roundworms) Chemical hazards: chemical substances that occur naturally in foods (pplant toxins) and those added to food (antibiotics) Physical hazards: bone, metal, plastic, other foreign matter that can damage consumer if ingested Bacterial Causes Foodborne infection  Invade intestinal tract  During colonization, epithelial cells lining intestine are damaged, disrupting uptake of solutes into body of cells  Results in imbalance in osmotic pressure, causing water to be secreted from tissues back into intestinal tract  Excess of water responsible for loosening of stool (diarrhea)  Damage of intestinal lining sends message to brain that triggers vomiting response  12 hours – 2 days  Examples: Salmonella, Yersinia, Shigella Foodborne intoxication  Produce toxin in food during growth  Foods contaiminated with toxin-producing or ganims (Staphylococcus aureus or Clostridium botulinum)  Onset of disease is very fast  Examples: E. coli Foodborne intoxification  Caused by ingestion of bacteria that once inside small intestine, produces toxin  Toxins absorbed by body, reaching kidneys where they cause substantial damage to convoluted tubules Mycotoxins from molds  Compounds have no apparent usefulness to mold  use up amino acids, acetate, pyruvate to prevent over accumulation of compounds  Range in toxicity (vomiting, to gangrene, bone marrow destruction, renal disorders, liver cancer) Virus Transmission  Incubation period for foodborne viral illness is usually several weeks  time viral particles invade host cells to replicate  Transmission can be through fecal-oral route  Ex. food handler suffering from hepatits A doesn’t wash hand after restroom  hands contaminated with fecal material that contains viral particles  touching foods that are to be eaten transfers virus to unsuspecting consumer Ingestion of parasites Protozoa  Typically harbored in intestinal tract of animals  When parasite is shed in feces of animal, it is in form of a cyst  cysts can contaminate surface of meat, thus be ingested through consumption of undercooked meat  Once inside body, cysts germinate growing cells that persist inside body for life  Onset of disease is typically at least one week Giardia lamblia – giardia occurs in form of pear-shape cyst, which germinates upon ingestion  One cyst yields 2 trophozoites  have 8 flagella that help propel them by falling-leaf type of motility  Trophozoites penetrate intestinal wall but not deep  cramps, nausea, weight loss, severe diarrhea, vomiting, flatulence  Onset is 1-2 weeks and up to 3 months  Highly contagious, with contaminated water and meat being prime sources of infection Toxoplasma gondii – harbored in house cats  Oocysts in fecal material are ingested  pass to intestine where they release 8 sporozoites  Pass through intestinal wall into circulatory system  Able to multiple fast in many parts of body  Referred to as tachyzoites and forms clusters surrounded by protective wall  Then called bradyzoites – don’t grow but persist in body for life o When immunity suppressed, bradyzoites break and release tachyzoites, which multiply rapidly bringing another acute infection  easily transmitted through placenta  Cysts destroyed by heating and freezing Cryptosporidium and cyclospora – exist as oocyts are found in untreated water  Oocysts resistant to chlorine  have implicated in outbreaks related to swimming activities  Once ingested, oocysts give rise to 4 sporozoites in intestinal or respiratory tract o Sporozoites attach to surfaces, developing feeder organelle that helps parasite ingest nutrients from host o Sporozoite transforms into trophozoite and then to schizont o Schizont releases several merozoites  penetrate other epithelial cells of intestine o Merozoites undergo cell division and give rise to 8 oocysts (some thin wall and some have thick wall) o Thin-wall oocysts give rise to autoinfection since they penetrate the intestinal wall o Thick walled oocysts shed in feces of sputum and infect other people who ingest material contaminated with feces  Symptoms develop within 2-14 days with water diarrhea, anorexia, weight loss, dehydration, abdominal discomfort lasting 3 weeks Flatworm  Exists in form of eggs in soil  Cattle ingest eggs and once inside, eggs release embryo, which penetrate intestinal tract of animal  Embryos will travel to other tissues, such as muscle and develop into larvae  Consumption of meat from these animals will result in ingestion of larvae by humans, causing disease Taenia saginata (beef) and taenia solium (pork) – intermediate hosts for parasites with humans being definitive hosts  Worms do not have vascular, respiratory, or digestive systems  use host to obtain nourishment  Eggs in soil ingested by cattle or swine  also ingestion can occur by coprophagy (feces infected with eggs directly eaten by animal) o Eggs called oncospheres  release embryos inside intestinal tract of host o Embryos penetrate intestinal wall and carried to muscles, tongue, heart by circulation o In tissues, larvae called cysticerci over 3 month period  In this stage, larvae called cysticercus bovis (beef tapeworm) and Cysticercus Cellulosae (swine tapeworm)  Humans ingest in undercooked beef and pork  Adul
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