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Food Safety > Factors Afecting Microbial Growth in Food > Flashcards

Factors Afecting Microbial Growth in Food Flashcards

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1
Q

Microbial growth phase :

A
  1. lag
  2. log
  3. Staionary
  4. Death
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2
Q

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

A

Lag

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3
Q

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

A

Log: Exponenial growth phase

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4
Q

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

A

Staionary phase

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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

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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.

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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.

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8
Q

Coliforms are easy to

A

culture

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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

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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

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11
Q

bacteria uilized Nitrogen to

A

to produce cellular proteins and enzymes

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12
Q

bacteria uilized Nitrate and ammonia to

A

produce amino acids that can be used to make proteins

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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)

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14
Q

Water acivity ranges

A

from 0 to 1.0

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15
Q

Microorganisms have …aw for growth

A

maximum, opimum, minimum

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16
Q

Bacteria can’t grow

A

pure wate

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17
Q

Bacteria the maximum aw is always

A

0.99

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18
Q

Bacteria require higher aw’s than

A

yeast and molds

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19
Q

Need to know minimum aw of microorganisms in order to

A

prevent their growth and spoilage of food

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20
Q

Reduce water acivity by

A

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

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21
Q

Cl.botulinum and Salmonella

required for Aw

A

0.93 aw

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22
Q

Most Bacteria required for Aw

A

0.099 aw

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23
Q

Most Yeasts required for Aw

A

0.88 aw

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24
Q

Halophilippic Bacteria required for Aw

A

0.75 aw

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25
Q

Extreme Osmophiles eg.molds&yeast required for Aw

A

0.61 aw

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26
Q

Bacteria optimal pH

A

6 to 8 ph

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27
Q

Yeast optimal pH

A

4.5 to 6.0 ph

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28
Q

Fungi optimal pH

A

3.5 to 4.0 ph

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29
Q

Once inside the bacterial cytoplasm the acid dissociates because

A

cell cytoplasm has a higher pH

30
Q

Bacteria maintain internal pH near neutral to

A

to prevent conformaional changes to proteins, enzymes, nucleic acid and phospholipids

31
Q

when the organic acids dissociate in the bacterial
cytoplasm
That are generated

A

Protons

32
Q

The protons are extruded by using energy in the form of ATP this causes

A

depleion of the cellular energy and death of the cell.

33
Q

There are two ways to measure acidity of a food:

A

• By “itratable acidity”
Measure HA “acive form”

• By “pH”
Measure free protons

34
Q

ionize

completely in aqueous systems

A

Strong acids such as

  • HCl (Hydrochloric acid),
  • H 2SO4(sulfuric acid),
  • H 3PO4(phosphoric acid)
35
Q

What Factors afecing the selecion of animicrobial agents?

A
  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
Q

Frist chemical preservaive permited by FDA

A

Sodium benzoate

37
Q

pH of Foods:

Food may be naturally

A

acidic

38
Q

Most active against yeast and molds

Major uses in beverages, juices, and buter

A

Benzoic Acid

39
Q
  • Major usage in salad dressings, fruit juices, and cotage cheese
  • Potassium salt is the most widely used form
A

Sorbic acid

40
Q

Aceic acid

A
  • 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
Q

Propionic acid

A
  • Efecive against molds, but no efect on yeast
  • Major usage baked goods
  • Calcium salt most used form
42
Q
  • Efecive against molds, yeast, bacteria

* Flavor problems and hypersensiivity

A

Sulfites

43
Q
  • Efecive against C. botulinum
  • Used in cured meat products
  • Reacts with myoglobin to give cured meat color
A

Nitrite

44
Q

• Efecive against yeast and molds, Gram posiive bacteria
• Used in ariicial sweeteners, baked goods, and few salad
dressings
• pKa = 8.47

A

Paraben

45
Q

Antimicrobial agents in common foods

A
  • Bread: Natures own 100% whole wheat
  • Salad dressing: Olive garden Italian
  • Beverage: Coke – diet coke
  • Margarine: Parkay
46
Q

proteins act as

A

buffers

47
Q

Highest pH in nature,

A

Egg white

48
Q

Compounds added to foods primarily for efects other than antimicrobial .

A

Indirect Animicrobials

49
Q

Antioxidant used primarily to

A

prevent auto-oxidation of lipids.

50
Q

agents used to impart aromas and flavors

A

Flavoring

51
Q

Flavoring such as

A

Diacetyl,Menthol

52
Q

Diacetyl efecive

A

against Gram-negaive bacteria and fungi.

53
Q

Diacetyl prevents the

A

uilizaion of arginine by reacing with arginine-binding proteins

54
Q

imparts peppermint like aroma is inhibitory against

Staphylococcus aureus and E. coli

A

Menthol

55
Q

are used primarily as lavoring and seasoning agents in foods.

A

Spices and Essenial Oils

56
Q

Naturally occurring animicrobials in Milk:

A

Lactoferrin
Lactoperoxidase
lysozyme

57
Q

Naturally occurring animicrobials in Egg whites:

A

Lysozyme

Conalbumin

58
Q

Animicrobial proteins

A

Bacteriocins

59
Q

Bacteriocins are

A

proteins produced by bacteria
more efecive at an acidic pH
Mainly efecive against Gram-posiive bacteria

60
Q

Increase aeration of food by grinding or Slicing increases the redox potenial
✅❌

A

✅

61
Q

Microaerophilic bacteria:

range

A

3%-6%

62
Q

Microaerophilic such as

A

Campylobacter

63
Q

Facultaive anaerobes such as

A

E. coli, Shigella, Salmonella

64
Q

Lowest temperature microbes can grow

A

Minimum

65
Q

Heat treatment (sterilizaion) can be used to

A 
kill all microorganisms in foods
to destroy undesirable enzymes 
 to destroy toxins 
Ready-to-eat foods are heated to destroy Pathogenic
bacteria
66
Q

Factors to consider in heat treatment:

A

Nature of Food
Aw
ph
Antimicrobial content

67
Q

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)

A

Thermal Death Time (TDT)

68
Q

the decimal reducion ime, ime required too destroy 90% of the organisms or 1 log cycle.

A

D Value

69
Q

the degrees Fahrenheit required for the thermal

destrucion curve to traverse one log cycle.

A

z Value

70
Q

Time in minutes required to destroy a given number of

the organisms in a speciic food product at 250°F (121°C).

A

F Value

Food Safety (11 decks)

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