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24 Cards in this Set

  • Front
  • Back
What is water activity and how does it pertain to bacteria?
It is a comparison of the residual humidity of water to a particular food. Bacteria like Aw above 0.60
How can you control water activity in manufacturing
drying, concentrating, adding salt, add sugar, add glycols
What is +Eh? -Eh, +/-Eh?
It is the oxi-red potential. Anerobes like -Eh, Aerobes like +Eh.
What nutrients do microorganisms require to grow?
energy source (carbos, am acids)
Carbon source
N source
Describe extrinsic factors and how you can control each.
1. Temperature (refridgeration, freezing)
2. Relative Humidity (packaging, modified atmosphere)
3. Prescense of Gases (packaging, modified atmospheres (CO2 + O3 = antimicrobial)
Name the "KILL STEPS"
Pasteurization, Canning, Cooking, Irradiation, High-Pressure Treatment, Fumigation
Name the two main sporeforming bacteria genera
Bacillus (cereus), Clostridium (botulism)
Draw a picture of a spore and name the main parts of its structure
Why is DPA so important? *What does it stand for?
Dipicolinic Acid, Prevalent in spore cortex, dehydrates and protects spore core. Main resistance front to outside conditions. Is building block of peptidoglycan.
What is a vegetative, dormant, activated, and germinated spore?
Vegetative= bacteria in growth phase. Can reproduce with nutrients. (exp phase, lag phase, etc.)

Dormant Spore=After sporulation in less than optimal condition. Conserves cell DNA for time when conditions improve.

Activated Spore= Metabolism started again when conditions are optimal. DPA excretion, SASP degradation, loss of spore resistance, initiation of protein synth.

Germinated Spore= Synth of Amino Acids and Nucleotides, Cell Wall and Membrane Synth. DNA replication. Cell outgrowth.
What are two micro-organisms with zero tolerance standards?
L. monocytogenes (RTE Meat) - 0/25g
E. coli O157:H7 (Ground Beef) - 0/25g
Enterobacter sakazakii (infant form) - 0/25g
Name the different types of microbiological methods. Name prominent examples.
Culture (TPC, Petrifilm), Microscopic, Chemical, Physical, Biochemical, Molecular (PCR, TAP-PCR), Immunological (Preggy Test, ELISA), Bioassays
What is the equation for plate count?
what is an antigen
a protein (foreign substance) that triggers antibody production as part of an immune response
Describe how an ELISA works
Describe Ribotyping
Use of nucleic acid probes to recognize ribosomal genes. Reproducable.
Describe PFGE
Pulsed Field Gel Electrophoresis. Discriminating typing method that features 360 degree electrical current to get the best resolution for large stranded DNA strands.
Describe PCR
Typing test. Two primers (short nucleotides) that are complementary to a double stranded helix are added. Denaturation (unraveling double stranded DNA), Annealing (attachment of primers to DNA), Polymerization (extension and duplication of DNA).
What is an Infection, Intoxication, Toxico-Infection?
Infection- Cells ingested and cause symptoms

Intoxication: Cells produce toxin on food matrix which makes host sick

Toxico-Infection: When cells are ingested and produce toxins IN BODY.
What is an indicator organism?
Naturally occuring organism in food or food processing where it's presence is used as an assessment of the occurence of other organisms or conditions
Why are indicator organisms tested rather than testing for pathogens?
Indicators are usually present in higher concentrations, so they are easier to detect
What are the characteristics of an ideal indicator microorganism
1. Present and detectable in foods whose quality is assessed

2. Growth or #'s should have negative correlation with quality

3. Easily detected, distinguishable

4.Grows in short period of time

5. Growth not affected by other components in food

6.Ability to survive and grow like target

7.Stable characteristics - no mutations
What is difference between indicator and surrogate microorganism
surrogate is added, indicator naturally present
Name some pathogen indicators
E.coli for O157H7

Listeria spp. for Listeria monocytogenes