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FDSC442 > 14 - physical methods for food preservation > Flashcards

14 - physical methods for food preservation Flashcards

1
Q

what is the Decimal reduction time (D value)

A

the time it takes of a 10-fold reduction in the number of survivors at a given temperature

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2
Q

What are the factors that will affect the heat transfer

A
  1. product type 2. container shape 3. container size 4. container material 5. agitation 6. temperature of heating medium
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3
Q

The greater the D value and the more ___ is an organism

A

resistant

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4
Q

The higher the temperature and the ___ is the D value

A

smaller

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5
Q

what is the thermal resistance plot

A
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6
Q

What is the survivor plot

A
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7
Q

A large Z value indicates that an organism is ____ to heat

A

resistant

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8
Q

What is the F value

A

The time in minutes it takes for a population of a specific organisms (specific temperature and z value) to acheive a target level. For c. bottulinum it is 12D.

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9
Q

What is the difference between the D value and the F value?

A

•The difference between D value, which defines the time it takes to reduce the population by 1 log, F value represents the time it takes to get the population to a specific level (i.e. 101 or sterile)

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10
Q

What is the F value of C. Botulinum if the D value is 0.21

A

•C. botulinum has a D121C value of 0.21 minutes, and a Z value of 10C. Therefore, to achieve commercial sterility at F121C you multiply 0.21 minutes by 12 which equals 2.52 minutes

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11
Q

•Commercial sterility of food products is the application of heat that renders the food free of:

A
  1. Microorganisms capable of reproducing in the food under normal non-refrigerated storage and distribution temperatures
  2. Viable microbial cells or spores of public health significance
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12
Q

What are the mechanisms of bacteria that make them more resistant to heat?

A
  • higher GC in DNA
  • Crosslinking disulfide bonding
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13
Q

•. if the aw, pH, or antimicrobial constituents are already stressing the bacteria out, you’ll need ____(less/more) heat to kill them

A

less

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14
Q

Aspectic processing is not used for __ and ___

A

low acid foods and particulat containing foods

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15
Q

are toxin affected by freezing?

A

no

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16
Q

How does freezing will presrve foods

A

because of the freeze/thaw cycle that can effect the cells
becuse of the freezing that stops the metabolic activity of most food-borne microorganisms
Because it will rduce the water activity (only xerotolerant can grow –> some yeast and fungo can)

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17
Q

•Gram-____ bacteria survive freezing better than Gram-___ bacteria

A

positive survive better than gram -

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18
Q

Are parasite destroyed by freezing

A

yes

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19
Q

which is better to kill microbial cells rapid or slow freezing

A

slow freezing because bigger crystals

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20
Q

Organisms that can resist the freezer needs to be :

A

xerotolerant (low Aw)
cryophilic, psychrophilic or psychrotrophic (cold resistant)

21
Q

___water is essential for microbial growth and survival

A

Unbound

22
Q

What is the formula of the water activity

A

Aw = P / P0

23
Q

What is the relation between the equilibium relative humidity and the Aw

A

ERH (%) = aw x 100

24
Q

T or F : the relation between the moisture content of foods and the Aw is linear

A

false

25
Q

What are the 3 categories of foods based on their Aw

A 
High moisture (over 0.9)
Intermidiate moisture foods (between 0.65 and 0.9)
Dry foods (lower than 0.65)
26
Q

Maple syrup is an ___ moisture food

A

intermidiaite

27
Q

__ and ___ can be an issue for maple syrup

A

yeasts and molds

28
Q

when boiled at lower temperautres, the maple syrup can be spoiled by ____

A

spoiled by LAB

29
Q

What is the minimal Aw that is needed by spoilage bacteria

A

0.95

30
Q

What is the minimal Aw that is needed by Listeria, and V.paraheamolyticus

A

o.91-0.95

31
Q

What is the minimal Aw that is needed by S.aureus

A

0.85

32
Q

____ have aw requirements that are lower than those of bacteria

A

Yeasts

33
Q

Can molds produce toxins in xerophilic conditions

A

no

34
Q

What is the organisms you are most likely to find in xerophilic conditions

A

molds

35
Q

is there any spoilage yeasts

A

yes

36
Q

Why is there no mold growth at higher Aw

A

because bacteria grow and they will produce fungicides

37
Q

T or F : lowering the Aw will kill the microorganisms

A

False, it will only inhibit their growth but they can stay dormant and multiply when there is an increase in the Aw

38
Q

what is another factor other than Aw in the presrvation by decreasing water availability that will inhibit the microorganisms

A

the humectant used to lower the Aw, for example glycerol will permetate the bacterial membrane and have different effect than the sucrose

39
Q

How does the ionizing radiation works

A

using the gamma and x-rays to target the DNA because of the creation of rective oxygen species

40
Q

the ____ the genome, the greater the resistance to ionizing radiation

A

smaller

41
Q

What is the advantage of gamma radiation

A

•The advantage is radiation has a high penetration power, and the energy is constant over the duration of the treatment, it is a continuous source that doesn’t need to be turned off

42
Q

What is redappertization?

A

. Involves a high dose (10 to 75 kGy) to produce commercial sterility

43
Q

What is Radicidation?

A

. Involves medium dose (1 to 10 kGy) to produce an equivalent effect to thermal pasteurization – effective against vegetative bacteria but spores are not inactivated

44
Q

What is Radurization

A

Involves low dose irridation (0.05 to 1 kGy) to control the presence of insects in grains or stop the sprouting of potatoes, or delay fruit ripening (because it lower ethylene production)

45
Q

What is HPP ?

A

•High pressure processing (HPP) involves treating food with pressures in the range of 100 to 600 MPa, which will inactivate most bacteria, yeasts, molds, and viruses (spores survive)

46
Q

What is PEF?

A

application of shor burst of high voltage between two electrodes (food inbetween) to eliminate vegetative cells

47
Q

Does HPP kills spores

A

no

48
Q

Does PEF kills spores

A

no

49
Q
A

FDSC442 (19 decks)

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