Exam 4.3

• What methods are used to preserve food?

  *Desiccation (beans, rice)

  *High-osmotic pressure (salt-cured foods, high sugar content)

  *Fermentation (acid production from ferm increases longevity)
• What are the three classes of food spoilage?

  *Perishable food (fresh fruit/vegetables/meat)

  *Semiperishable food (potatoes, nuts)

  *Stable/nonperishable food (flour, sugar)
• Industrial food canning

  *Blanching = hot water treatment (lowers microbial load - can't kill spore formers)

  *Retort = huge autoclave (12D treatment, remaining bacteria are thermophilic)
• Canned food spoilage

  *Flat sour spoilage = thermophiles grow, can doesn't swell

  *Thermophilic, anerobic spoilage = food not stored correctly, thermophiles grow + can swells

  *Putrefactive anaerobic spoilage = retort not working correctly (can could leak, mesophiles grow, botulism)
• How are aseptic packaging, radiation treatment and high-pressure treatment used in food prep?

  *Aseptic packaging = heat or UV sterilized, heat treated foods are added to them

  *Radiation treatment = highly lethal to microbes, forms of ionizing radiation (x-rays, gamma rays, e- beams), irradiated food is marked w/radura --> not high-throughput

  *High-pressure treatment = pre-cooked, pre-packaged foods, submerge them in water at high pressure
• Why are hops added to beer?

  *To act as antibacterial compounds

  *Contain humulones
• Food poisoning

  Disease resulting from ingestion of foods containing microbial toxins
• Food infection

  Microbial infection resulting from the ingestion of pathogen-contaminated food, followed by growth of pathogen in the host
• Where would you expect to pick up each type of poisoning/infection?

  *Staphylococcal food poisoning: common foods (custard, poultry, eggs), heat stable enterotoxins

  *Clostridial food poisoning: usually in meats, botulism (exotoxin), soilborne + in sewage, canning + cooking usually kills these

  *Salmonellosis: chickens + pigs à custards, sausages, meringues, eggnog

  *Pathogenic Escherichia coli: all intestinal pathogens, produce verotoxin, uncooked or under-cooked meat

  *Campylobacter: poultry, pork + shellfish, invades epithelium of small intestine

  *Listeria: causes listeriosis, infects phagocytes, ready-to-eat meats, fresh soft cheeses, unpasteurized dairy products

  *Yersinia: contaminated meats + dairy

  *Bacillus: food that is cooked + left to cool slowly

  *Norovirus

  *Protists = enteritis: from fresh fruits

  *Prions: from cows
• Know the selective/differential characteristics of Eosin Methylene Blue Agar (EMB)

  *Selective: Eosin and methylene blue inhibit growth of Gram-positive cells

  *Differential: lactose fermenters form nucleated colonies
• Know the selective/differential characteristics of Hektoen Enteric Agar (HEA)

  *Selective: Bile salts (inhibit most Gram +)

  *Differential: lactose/sucrose/salicin fermentation gives lighter colonies

  *Differential: thiosulfate/Fe (sulfate reducers develop black centers)