This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Microbes in food: The good, the bad, and the ugly • Bacteria appear 3.5 billion years. YEAST • Different types of microorganisms : one is yeast. More like humans than bacteria. Have membrane, nuclei, chromosomes. Used in food science to make bread, beer, wine Fungi and Molds Positive roles: Flavor in cheese, Oriental fermented foods, Mushrooms. Generally spoilage/quality issue: mycotoxins, aflatoxins Viruses • are not alive they need human cells to grow …difficult to study on a petri dish. Viruses don’t grow in food ..they are just transmitted. 60% foodborne illness are caused by viruses • Foodborne viruses: Norwalk viruses (now Norovirus), Hepatitis A. Transmission of Foodborne Viruses: The “fecal oral” route, Bad water, Shell fish from polluted water, “Finger licken good” Bacteria • grows by doubling Yeast grows by budding …bud off another yeast then become another. Then bud off again . Get bud scares and then can’t reproduce again .Molds grow by hyphoelongation- just get longer and longer • Good bacteria: Nitrogen fixation in plants; Legumes –bean that has bacteria in the roots ,Corn-nitrogen users ,Soybeans-nitrogen fixers • We have ten times more bacteria in us or on us than we do human cells … bc bacteria is extremely small • The bacterial growth cycle has four phases: lag, logarithmic or exponential, stationary, death • Bacteria grow by doubling. One bacterium can grow to one million bacteria in 20doublings! • Philosophies of Microbial Control; The 5 K's: Keep it hot. Keep it cold. Keep it moving. Keep it clean. Kill it. CommodityApproach: Know which organisms are associated with which foods and focus on them. Hitchhiker's Guide to the Galaxy: Everything is related to everything else.(Foods are ecosystems) if a farmer puts up fences, for instance. Hazard Analysis Critical Control Points - Uses 20:20 hindsight and Murphy's Law to our advantage. Cant test all of the food The Miracle (or curse) of Exponential Growth N = Noe kt . o N = Number of bacteria at any time, t o No= Initial number of bacteria o k= Rate constant, influenced strongly by temperature, also influenced by environmental conditions o The initial is equal to the final number o In the exponent temperature is included as well as time • THE "40-140" RULE. FOODS SHOULD BE HELD: BELOW 40° FOR ABOVE 140°F. COROLLARY: WHEN HEATING OR COOLING, BRING FOODS THROUGH THE 40-140°F REGION AS RAPIDLY AS POSSIBLE. • FDA estimates poor hand washing contributes to 80 million cases in U.S. • Top Ten Causes of Outbreaks 1. Improper cooling 43.7%. Harder to cool than heat. Improper cleaning of equipment/utensils 5.4% • Old Model - Safety At Some Place (Do What Government Tells You) Pinpoint Problem, Provide Solution, Promulgate Regulation, Punish Violators • New Model - Safety Depends on Whole System. “Farm to Fork” (Achieve Government Dictated Outcome ) Seed Soil Fertilization Agricultural practices Climate Harvest Storage...
View Full Document
- Fall '08
- Bacteria, Food processing, Shelf life, high hydrostatic pressure, non-thermal food processing