FOOD-SCI 150 Study Guide - Fall 2018, Comprehensive Midterm Notes - Ph, Bacteria, Yeast
12 Oct 2018
School
Department
Course
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FOOD-SCI 150
MIDTERM EXAM
STUDY GUIDE
Fall 2018
GI Tract has 13 trillion “bugs”
Soil has 2.5 billion
Sponge/Month has 7.2 million/Clean: 1,000-100,000 per tooth Dirty: 100 million-1 billion per
tooth
Phone has 25,000 microbes
Toilet has 49 microbes
History of Microbiology
● Anton Van Leeuwenhoek 1632-1723
○ One of the first scientists to observe microorganisms
○ Microscope survived but he never told anyone how to use it
● Spontaneous generation (life will spontaneously arrive)
● Louis Pasteur 1822-1895
○ Developed pasteurization to pasteurize wine
○ Disproved spontaneous generation
● Robert Koch 1843-1910
○ First to conceptualize and prove germ theory
○ Took the blood from the sick sheep and grew it outside of the animal
○ Koch’s postulates
■ The microorganism must be demonstrable in all cases of the disease
■ The microorganism must be isolated from the diseased animal and grown
in pure culture
■ The microorganism from this pure culture must cause the same disease
when inoculated into a healthy animal
■ The experimentally infected animal must contain
● Types of microorganisms in foods
○ Fungi
■ Molds
● Multicellular- from tubular structures called hyphae
● Tend to produce colors
● Fuzzy-cotton-like
● Produce many spores which can be transported via dust
● Can withstand extremes in pH, water activity, temperature for
growth
● Spoilage, mycotoxins, fermentation
■ Yeast
● Single cell
● Larger than bacteria
● Divide by budding
● More resistant to extremes in pH, water activity, temperature than
bacteria
● Fermentations, spoilage
■ Bacteria
find more resources at oneclass.com
find more resources at oneclass.com
● Bacterial shapes can vary, rod or bacillus or cocci (round) or spiral
● Some bacteria are motile, flagella
● Some bacteria produce spores
○ Spores are dormant (non-growing) forms of bacteria that
are highly resistant to heat, drying, and cleaning agents
Bacteria Growth
● Bacteria
○ Single cell
○ Division by binary fission
Microbial growth curve
● Lag phase
○ Period of adjustment
● Exponential growth phase
○ Period of rapid growth (1 → 2,2, 4,4, 8…)
● Stationary phase
○ Lack of nutrients signal period of little-to-no growth but cells are still metabolically
active
● Death phase or sporculation
○ Long after stationary phase, cells die due to lack of nutrients and metabolic waste
○ Cells that sporculate will do so in stationary phase under the right conditions
Generation time
● The amount of time it takes for 1 bacterium to divide into 2 bacteria
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Sponge/month has 7. 2 million/clean: 1,000-100,000 per tooth dirty: 100 million-1 billion per tooth. One of the first scientists to observe microorganisms. Microscope survived but he never told anyone how to use it. First to conceptualize and prove germ theory. Took the blood from the sick sheep and grew it outside of the animal. The microorganism must be demonstrable in all cases of the disease. The microorganism must be isolated from the diseased animal and grown in pure culture. The microorganism from this pure culture must cause the same disease when inoculated into a healthy animal. Produce many spores which can be transported via dust. Can withstand extremes in ph, water activity, temperature for growth. More resistant to extremes in ph, water activity, temperature than bacteria. Bacterial shapes can vary, rod or bacillus or cocci (round) or spiral. Spores are dormant (non-growing) forms of bacteria that are highly resistant to heat, drying, and cleaning agents.
