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Microbiology > Spoilage > Flashcards

Spoilage Flashcards

1
Q

When does spoilages start to become noticable

A

10^7 cells per gram

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2
Q

Generation time

A

time needed for the population to double

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3
Q

Which enzymes are present in aerobic MO’s that break down ROS?

A

superoxide dismutase and catalase

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4
Q

Obligate aerobe

A

Needs O2

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5
Q

Microaerophile

A

requires 2-0% O2, damaged by 20%

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6
Q

Facultative anaerobic

A

does not require O2, but grows better with it

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7
Q

aerotolerant anaerobe

A

grows equally well with or without O2

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8
Q

obligate anaerobe

A

Dies with O2 present

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9
Q

A lower pH gives a higher or lower redox potential?

A

higher Eh due to many H+

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10
Q

What happens when meat is vacuum packed?

A

There is residual respiration which consumes the O2 and produces CO2, this inhibits some MO’s.

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11
Q

Why does meat become pink/grey in a vacuum?

A

Because myoglobin can not bind to O2 anymore

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12
Q

xerophilic

A

grows on dry foods

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13
Q

osmophilic

A

grow in high concentrations of unionized compounds (sugar)

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14
Q

halotolerant

A

Grows in salted procts

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15
Q

Halophilic

A

Requires high levels of salt

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16
Q

What do microbicidal preservatives do?

A

Kill the MO’s

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17
Q

What do microbistatic preservatives do?

A

Prevent the growth of MO’s

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18
Q

Why would you add sulphite to a food

A

To acidify the product

19
Q

Why would you add nitrite to a product?

A

To target clostridium and for the colour of meat.

20
Q

psychrophile

A

Between -5 and -20 degrees

21
Q

Psychrotolerant

A

Between -5 and -35 degrees

22
Q

mesophile

A

Between 4 -47 degrees

23
Q

Thermophile

A

Between 40-90 degrees

24
Q

Thermotolerant

A

Will survive mild pasteurization

25
Q

Competition between MO’s

A

Growth of both MOs is suppressed, or one doesnt care, and the other one is suppressed

26
Q

Symbiosis

A

Both need from eachother

27
Q

Mutualism

A

Both benefit from each other

28
Q

Commensalism

A

B benefits from A, A doesnt mind

29
Q

Antagonism

A

A lowers growth of B

30
Q

Challenge test

A

Inoculate product and follow the growth of the MO’s

31
Q

Storage test

A

Follow the fate of the product without spiking

32
Q

Predictive microbiology

A

describe fate of MO by mathematical models

33
Q

What is the average z value of vegetative cells?

A

5 degrees

34
Q

Whats is the average z value of spores?

A

10 degrees

35
Q

What is the lethal rate

A

the relative inactiviation rate at a certain temperature

36
Q

F value

A

integrated lethal effect

37
Q

What will happen after meat is slaughtered?

A

There will by glycoysis with the oxygen that is still in the animal. This will cause lactic acid production and inactivate glycolytic enzyme.

38
Q

What will happen when you vacuum pack meat

A

Because of the low oxygen pseudomonas will not be able to grow, but LAB will take over. Meat will turn grey because of low oxygen in the myoglobin

39
Q

What will happen to meat in MAP

A

Red colour will remain. CO2 will disolve into the meat at a low temperature, this makes the LAB more dominant.

40
Q

What will happen to meat when you freeze it

A

There will be no bacterial growth due to the low aw and temperature, but the growth can continue when defrosting.

41
Q

Why is fish so perishable?

A

Because of the high pH and because there is no post mortem acidification.

42
Q

Which groups of MO’s are targeted by vacuum packaging?

A

Anaerobic microorganisms

43
Q

Which groups of MO’s are targeted by heat treatment 90 degrees

A

Vegetative cells and non-resistant spores

44
Q

Which groups of MO’s are targeted by cooled storage

A

Mesophils and slows down growth of psychrotolerant MO’s

Microbiology (4 decks)

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