Food Microbiology Exam 2


Terms in this set (...)

Plan variable letter that represents the total number of samples to be tested.
Plan variable letter that represents the number of samples having counts lower than M
Plan variable letter that represents minimum counts
Plan variable letter that represents maximum counts
Direct count, dye reduction test, MPN, Standard Plate Count,
4 Conventional methods
Less materials, little training, organism not diluted out.
3 primary advantages of spiral plater
Expensive, Food particles may block stylus
2 primary disadvantages of sprial automated plater
Cellulose, polycarbonate
2 most commonly used membranes for membrane filtration food analysis
Direct epifluorescent filter technique
Type of membrane filtration where viewing is done with special microscopy
acridine orange
DEFT membranes are stained with
3 to 6
DEFT membranes are grown on agar for _____ hours
Hydrophobic Grid Membrane Filtration
Method of filtration that employs a membrane filter with 1600 wax grids
12 to 24
HGMF membranes are grown on agar for ____ hours
restricts growth and colony size to individual grid
HGMF unique feature
Flow Cytometry, Impedance, Microcalorimetry
3 primary physical methods of detection/analysis
ATP, Limulus lysate assay for endotoxins, Lux gene
3 common chemical methods of detection/analysis
Resistance in an electric circuit to the flow of AC corresponding to the actual electric resistance to a direct current.
10 to 100 cells in 5 to 7 hours
Impedance sensitivity
IDT - impedance detection time
Time required to attain a threshold of 10⁶ to 10⁷ cells per mL (inversely proportional to the initial inoculum
Malthus assay
Type of assay using media based on metabolism of trimethyl-amine oxide (TMAO) to trimethyl amine (TMA) for detecting _____
impedance splitting
BacTrac System operates on ______ method and may be used to detect Salmonella
Method using measurement of enthalpy changed involved in the breakdown of growth substrates
Batch, Flow
2 Types of calorimeters
Flow cytometry
Measures cell components by fluorescence, absorbance, and light scatter
fluorescence isothiocyanate
When flow cytometry is being used to detect both proteins and DNA, the cell protein is stained with
propidium iodide
When flow cytometry is being used to detect both proteins and DNA, the cell DNA is stained with
lipid A
LPS is lipopolysaccharide and
Lysate protein
Most sensitive substance known for endotoxin from horse shoe crab
1.0 pg of LPS, less than 300 gram neg cells
Limulus Lysate sensitivity
both viable and non-viable cells detected
Limitation of Limulus Lysate test
ATP is measured by _______ system
In the presence of ATP ____ emits light
ATP - luciferase photon emission is measured by ____
Relative light units
Unit of measurement for luminometry
apyrase and triton x-100
Treatment of food samples with ____ and ____ can selectively destroy nonbacterial ATP
lux A and lux B
Two genes responsible for luciferase activity which produces photons
Lux gene luminescence
Method of transferring lux gene bearing phages
10 cells of E. coli in 10 minutes
Example of Lux gene luminescence sensitivity
End point or Quantal
Type of bioassay where the threshold dose required to elicit response is determined and compared with standard
End point
LD50 is what type of assay
lowest dose causing lethality
lowest toxic dose
Lethal concentration for 50 percent of test population
3M TECRA system is used to detect
3M TECRA is what type of test
Enterobacteriaceae, gram negative oxidase negative bacteria
BD EnteroPluri test detects
18 to 24 hrs at 36 degrees
BD EnteroPluri test incubation parameters
must be isolated in last 18 to 24 hrs, over 48 hours is unreliable
BD EnteroPluri test limitation time
gram stain, oxidase test
BD EnteroPluri test prerequisites
expired systems, improper procedure, mixed culture, non-gram negative oxidase negative sample
BD EnteroPluri test invalidated results due to (4)
Analytical Profile Index
Biomerieux API kits, API stands for
20 reaction cupules, 23 reactions in 4 hours
Biomerieux API kits main component ___ does ____
18 to 35 bases
Primer size
Thermus aquaticus
Taq polymerase from
PCR denature temp
50 to 70
PCR anneal temp
PCR extend temp
DNA visualization wavelength with Ethidium Bromide
Fast Blast
Alternative non-fluorescent visible stain
Restriction digestion, southern blot
Two methods of verifying PCR results
Class of Immunoglobulin most often used in immunoassays.
Alternate name for Variable region of an antibody
Alternate name for Constant region of an antibody
proteins or whole cells
Simple agglutination test detects
Primary antibody
What is bound to the well in a Sandwhich ELISA?
Bacterial Cell
What is bound to the well in a simple ELISA
Parabens (p-hydroxy-benzoic acid) is used primarily as a ____ in food.
both fungi and bacteria
Sorbic acid is added to food to inhibit
mold inhibitors
Proprionic acid and propionates are primarily used as
Yeast and molds
Benzoic acid is effective against which microflora?
Nisin is allowed in what product type?
Modified Atmosphere Packaging
MAP is
Equilibrium modified atmosphere
low O2 high CO2
EMAP parameters to prolong shelf life of vegetables
red meat
High O2 Map suitable for
Controlled Atmosphere Packaging
CAP is
Aluminum foil laminate, glass, metal
CAP requires one of these packaging types
International Symbol for irradiation
100 to 280 nm
Germicidal UV band
260 nm
Wavelength especially likely to create pyrimidine dimers
CS137 or CO60
Gamma rays are emitted from the excited nucleus of either
25-50 nm
Wavelength of Gamma Radiation
1 gray in Rads
I kGy in rads
Substantially reduces viable spoilage organisms, typically .75 to 2.5 kGy
radiation sterilization typically 30 to 40 kGy
equivalent to pasteurization - complete elimination of viable non-spore forming pathogeens except viruses 2.5 to 10 kGy
Food Irradiation can form peroxides under what conditions
Aerobic irradiation of lipids and fats.
what type of irradiation in what product leads to rapid rancidity?
Deinococcus radiodurans, 1.5 million
Worlds most radiation resistant organism...survives )____ rads
Does not raise temp/cook, no ice crystal, no harmful residues, can be used to treat packaged foods guaranteeing safety.
Irradiation advantages over heat, chemical, refrigeration, freezing.
28 to 42.8 F
Refrigeration range
10 degrees, 2 fold/doubles generation time
For every ________ decrease the rate of enzyme reactions _______.
Organisms that tolerate a broad range of cold temperatures
Organisms that tolerate a narrow range of cold temperatures
Low temperature spoilage organisms are mostly gram
Yersinia enterocolitica, Listeria monocyotgenes, Type II Clostridium botulinum
3 exceptions of pathogens that grow below 42.8
Temp shock, osmotic shock, protein denaturation/enzyme inactivation, mechanical damage due to ice crystals
4 Specific effects of freezing on microorganisms
yeasts and molds
Growth below 32 degrees is more likely to be
-29 F - pink yeast
lowest known microbial growth
14 F
Protozoa are generally killed when frozen below
Introduces double bonds in phospholipid fatty acid tails
Cold shock adaptation in Bacillus s.
Enzyme responsible for double bond formation in cold shock
Quick Freezing - small or large ice crystals?
Slow freezing = least or greatest temperature shock?
Slow freezing = accumulation of concentrated solutes or no solute imbalance?
No protective effect or adaptation
Quick freezing = protective effect and adaptation or no protective effect or adaptation