Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Food Safety > Factors Afecting Microbial Growth in Food > Flashcards

Factors Afecting Microbial Growth in Food Flashcards

(70 cards)

Start Studying
1
Q

Microbial growth phase :

A
  1. lag
  2. log
  3. Staionary
  4. Death
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Bacteria becoming adapt to new environment (pH, temperature, moisture, Nutrients). what phase?

A

Lag

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

bacteria increase rapidly, growth rate increases with time , condiions are opimal with growth. What phase?

A

Log: Exponenial growth phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Exhausion of nutrients and build-up of waste and 2nd metabolic products.
growth rate = death rate.

A

Staionary phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

No more growth cells are dying. If less than opimum condiions: lag is longer, log is more lat, and staionary is lower.

A

Death Phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Coliforms Deiniion

A

all aerobic and facultaive anaerobic,
Gram-negaive,
non-spore forming bacilli ferment lactose with acid and gas within 48 h at 35°C.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Coliforms They are a commonly used

A
  • indicator of sanitary quality of foods and water.

- indicate that pathogenic organisms of fecal origin may be present.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Coliforms are easy to

A

culture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Factors that afect growth
Intrinsic Parameters
(properies of food)

A

• pH: Lower then 4.6 grow best at neutral pH

• Water acivity Aw,
lower preferred

• Oxidaion-reducion potenial
Eh of substance is deined as the ease with which a substance loses or
gains electrons

• Nutrient content
Water, carbon, nitrogen, vitamin and minerals

• Animicrobial content
Eggs contain lysozyme, lavor compounds, milk contains lactoferrin

• Biological structures
Egg shell, skin on fruits, nuts have shells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q 
Factors that afect growth
Extrinsic Parameters (properies outside food)
A

• Temperature
Efects growth: refrigeraion or freezing, kills: heating

• Gases
Modiied atmosphere storage in 10% CO2

• ERH Equilibrium
relaive humidity, store foods at a humidity that will prevent up take of moisture

• Compeing microbes Microbes that produce baciocins

• Food packaging films
Vacuum package, edible ilms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

bacteria uilized Nitrogen to

A

to produce cellular proteins and enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

bacteria uilized Nitrate and ammonia to

A

produce amino acids that can be used to make proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Growth factors – some bacteria require vitamins and minerals.

A

• Magnesium
(enzyme cofactor especially for ATP reacions)

• Calcium
(cofactor for enzymaic acivity)

• Phosphorous
(nucleic acid, cofactor for enzymes)

• Sulfur
(amino acids and co-factor for enzymes)

• Iron (cofactor for enzymes)

• Cobalt
(consituent of B12, cofactor for enzymes)

• Potassium
(inorganic cat ion needed for osmoic balance of the cell)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Water acivity ranges

A

from 0 to 1.0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Microorganisms have …aw for growth

A

maximum, opimum, minimum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Bacteria can’t grow

A

pure wate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Bacteria the maximum aw is always

A

0.99

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Bacteria require higher aw’s than

A

yeast and molds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Need to know minimum aw of microorganisms in order to

A

prevent their growth and spoilage of food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Reduce water acivity by

A

dissolving compounds to bind moisture, such as Salt and Sugar ; also physical drying

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Cl.botulinum and Salmonella

required for Aw

A

0.93 aw

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Most Bacteria required for Aw

A

0.099 aw

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Most Yeasts required for Aw

A

0.88 aw

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Halophilippic Bacteria required for Aw

A

0.75 aw

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Extreme Osmophiles eg.molds&yeast required for Aw
0.61 aw
26
Bacteria optimal pH
6 to 8 ph
27
Yeast optimal pH
4.5 to 6.0 ph
28
Fungi optimal pH
3.5 to 4.0 ph
29
Once inside the bacterial cytoplasm the acid dissociates because
cell cytoplasm has a higher pH
30
Bacteria maintain internal pH near neutral to
to prevent conformaional changes to proteins, enzymes, nucleic acid and phospholipids
31
when the organic acids dissociate in the bacterial cytoplasm That are generated
Protons
32
The protons are extruded by using energy in the form of ATP this causes
depleion of the cellular energy and death of the cell.
33
There are two ways to measure acidity of a food:
• By “itratable acidity” Measure HA “acive form” • By “pH” Measure free protons
34
ionize | completely in aqueous systems
Strong acids such as - HCl (Hydrochloric acid), - H 2SO4(sulfuric acid), - H 3PO4(phosphoric acid)
35
What Factors afecing the selecion of animicrobial agents?
1. Antimicrobial activity 2. pH of the food product 3. Food composition 4. Processing and storage conditions 5. Solubility 6. Flavor 7. Cost 8. Markeing impact
36
Frist chemical preservaive permited by FDA
Sodium benzoate
37
pH of Foods: | Food may be naturally
acidic
38
Most active against yeast and molds | Major uses in beverages, juices, and buter
Benzoic Acid
39
* Major usage in salad dressings, fruit juices, and cotage cheese * Potassium salt is the most widely used form
Sorbic acid
40
Aceic acid
* Usage level limited by taste * More efecive against yeast and bacteria * Major usage in Pickled foods and natural bread * Sodium diacetate used in some breads
41
Propionic acid
* Efecive against molds, but no efect on yeast * Major usage baked goods * Calcium salt most used form
42
* Efecive against molds, yeast, bacteria | * Flavor problems and hypersensiivity
Sulfites
43
* Efecive against C. botulinum * Used in cured meat products * Reacts with myoglobin to give cured meat color
Nitrite
44
• Efecive against yeast and molds, Gram posiive bacteria • Used in ariicial sweeteners, baked goods, and few salad dressings • pKa = 8.47
Paraben
45
Antimicrobial agents in common foods
* Bread: Natures own 100% whole wheat * Salad dressing: Olive garden Italian * Beverage: Coke – diet coke * Margarine: Parkay
46
proteins act as
buffers
47
Highest pH in nature,
Egg white
48
Compounds added to foods primarily for efects other than antimicrobial .
Indirect Animicrobials
49
Antioxidant used primarily to
prevent auto-oxidation of lipids.
50
agents used to impart aromas and flavors
Flavoring
51
Flavoring such as
Diacetyl,Menthol
52
Diacetyl efecive
against Gram-negaive bacteria and fungi.
53
Diacetyl prevents the
uilizaion of arginine by reacing with arginine-binding proteins
54
imparts peppermint like aroma is inhibitory against | Staphylococcus aureus and E. coli
Menthol
55
are used primarily as lavoring and seasoning agents in foods.
Spices and Essenial Oils
56
Naturally occurring animicrobials in Milk:
Lactoferrin Lactoperoxidase lysozyme
57
Naturally occurring animicrobials in Egg whites:
Lysozyme | Conalbumin
58
Animicrobial proteins
Bacteriocins
59
Bacteriocins are
proteins produced by bacteria more efecive at an acidic pH Mainly efecive against Gram-posiive bacteria
60
Increase aeration of food by grinding or Slicing increases the redox potenial ✅❌
✅
61
Microaerophilic bacteria: | range
3%-6%
62
Microaerophilic such as
Campylobacter
63
Facultaive anaerobes such as
E. coli, Shigella, Salmonella
64
Lowest temperature microbes can grow
Minimum
65
Heat treatment (sterilizaion) can be used to
``` kill all microorganisms in foods to destroy undesirable enzymes to destroy toxins Ready-to-eat foods are heated to destroy Pathogenic bacteria ```
66
Factors to consider in heat treatment:
Nature of Food Aw ph Antimicrobial content
67
the time necessary to kill a given number of organisms at a specific temperature. (Temperature is constant and time needed to kill cells is determined)
Thermal Death Time (TDT)
68
the decimal reducion ime, ime required too destroy 90% of the organisms or 1 log cycle.
D Value
69
the degrees Fahrenheit required for the thermal | destrucion curve to traverse one log cycle.
z Value
70
Time in minutes required to destroy a given number of | the organisms in a speciic food product at 250°F (121°C).
F Value

Food Safety (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions