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Micro Lab > Experiments 1-4 > Flashcards

Experiments 1-4 Flashcards

1
Q

Microbes from Exp 1

A

Lactobacillus reuteri
Escherichia coli

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2
Q

EC cultured on

A

LB plates

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3
Q

LR cultured on

A

MRS plates

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4
Q

Gram stain purpose

A

Look at morphology
Distinguish gram + and - bacteria

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5
Q

Gram stain protocol

A
  1. Heat fix the smear
  2. Flood with crystal violet for 1 min
  3. Rinse
  4. Flood with iodine for 1 min
  5. Rinse
  6. Decolorize until colorless
  7. Flood with counterstain for 30 sec
  8. Rinse
  9. Blot dry
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6
Q

Thermal process designed to

A

Reduce the microbial load

Eliminate one or more spoilage organisms and/or pathogens in the product

Inactivate enzymes

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7
Q

Result of successful heat treatment

A

More shelf stable product

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8
Q

Increase death rate w/

A

Salt
Acid

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9
Q

Protective effect on microbes

A

Decrease in Aw
Increase in fat
Increase in protein

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10
Q

D value

A

Time (in minutes) to reduce a microbial population by 90% (1 log) in a specified heating medium at a specified temperature

Resistance to a certain temp

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11
Q

Thermal death time

A

Time (in minutes) to reduce a given number of organisms to 100 (essentially zero) in a specified medium at a specified temperature

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12
Q

Calculate TDT

A

Extrapolate survival curve

Or

D value x number of cells

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13
Q

Z value

A

Change in temperature (°F) required to cause the TDT curve to go through one log cycle

Sensitivity of an organism to changes in temp

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14
Q

Preventative techniques for spoilage

A

Specialized packaging
Use of natural preservatives
Heat treatment
Dehydration
Acidification
Purification of air quality
Decreasing water activity
Irradiation
Refrigeration or freezing
Addition of food additives

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15
Q

Mold growth factors

A

Oxygen availability
High mositure
Temp
pH
Nutrients

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16
Q

What does refrigeration do

A

Prolong the shelf life
Does not prevent all growth

17
Q

Inhibitors

A

Chemicals or substances added to another substance to slow down or prevent a reaction or change

18
Q

Amount of inhibitor depends on

A

Food product
Bacteria or fungi

19
Q

Shelf life

A

A guide for consumers showing the period until which food is safe and beyond which it will begin to deteriorate

20
Q

During shelf life,
a food should

A

Be safe for consumption

Maintain appearance, odor, texture and color for consumer appeal

Fulfill any nutritional claims made for the product

21
Q

Factors Affecting Shelf Life

A

Microbial Spoilage
Non Microbial Spoilage

22
Q

Microbial spoilage

A

Growth of bacteria, yeasts and molds

23
Q

Factors that affect product quality

A

Aw
pH
Temp of storage
Handling

24
Q

Non Microbial spoilage

A

Moisture
Chemical changes
Light induced changes
Physical tampering damage to the product
Rodent and pest damage

25
Q

Shelf Life Study

A

A meticulous study that studies all the possible factors affecting the stability and quality of a food product

26
Q

Direct Shelf Life Study

A

Pre-selected conditions for time periods longer than expected shelf life

27
Q

Indirect Shelf Life Study

A

accelerated study under more harsh conditions/ study using modeling techniques

28
Q

Milk characteristics

A

pH close to neutral
highly perishable
lots of nutrients

29
Q

Spread plating

A

100 uL
30-300 CFU

30
Q

Spot Plating

A

10 uL
3-30 CFU

31
Q

Gram positive bacteria

A

Thick layer of peptidoglycan in cell wall
Retain CV
Purple color

32
Q

Gram negative bacteria

A

Stain red
Thinner peptidoglycan wall
Don’t retain CV

33
Q

CFU/mL =

A

of colonies x dilution factor x uL to mL

34
Q

TSAYE Agar

A

Trypticase Soy Agar + Yeast Extract

35
Q

Nutrient Agar

A

Total bacterial count

36
Q

Yeast & Mold agar

A

Total yeast and mold count

Low temp incubation
Acidified

37
Q

Pasteurization

A

Heat process to reduce total bacterial populations to eat food safely

38
Q

Prepare w/v solution

A

Prepare a x% solution
Mix x g per 100 mL of the solute
Example

0.85% salt solution
0.85 g salt/100 mL solute

Micro Lab (4 decks)

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