14 - physical methods for food preservation

Question 1

what is the Decimal reduction time (D value)

Answer 1

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

Question 2

What are the factors that will affect the heat transfer

Answer 2

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

Question 3

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

Answer 3

resistant

Question 4

The higher the temperature and the ___ is the D value

Answer 4

smaller

Question 5

what is the thermal resistance plot

Answer 5

Question 6

What is the survivor plot

Answer 6

Question 7

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

Answer 7

resistant

Question 8

What is the F value

Answer 8

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.

Question 9

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

Answer 9

•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)

Question 10

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

Answer 10

•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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

• higher GC in DNA
• Crosslinking disulfide bonding

Question 13

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

Answer 13

less

Question 14

Aspectic processing is not used for __ and ___

Answer 14

low acid foods and particulat containing foods

Question 15

are toxin affected by freezing?

Answer 15

no

Question 16

How does freezing will presrve foods

Answer 16

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)

Question 17

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

Answer 17

positive survive better than gram -

Question 18

Are parasite destroyed by freezing

Answer 18

yes

Question 19

which is better to kill microbial cells rapid or slow freezing

Answer 19

slow freezing because bigger crystals

Question 20

Organisms that can resist the freezer needs to be :

Answer 20

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

Question 21

___water is essential for microbial growth and survival

Answer 21

Unbound

Question 22

What is the formula of the water activity

Answer 22

Aw = P / P0

Question 23

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

Answer 23

ERH (%) = aw x 100

Question 24

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

Answer 24

false

Question 25

What are the 3 categories of foods based on their Aw

Answer 25

``` High moisture (over 0.9) Intermidiate moisture foods (between 0.65 and 0.9) Dry foods (lower than 0.65) ```

Question 26

Maple syrup is an ___ moisture food

Answer 26

intermidiaite

Question 27

\_\_ and ___ can be an issue for maple syrup

Answer 27

yeasts and molds

Question 28

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

Answer 28

spoiled by LAB

Question 29

What is the minimal Aw that is needed by spoilage bacteria

Answer 29

0.95

Question 30

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

Answer 30

o.91-0.95

Question 31

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

Answer 31

0.85

Question 32

\_\_\_\_ have aw requirements that are lower than those of bacteria

Answer 32

Yeasts

Question 33

Can molds produce toxins in xerophilic conditions

Answer 33

no

Question 34

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

Answer 34

molds

Question 35

is there any spoilage yeasts

Answer 35

yes

Question 36

Why is there no mold growth at higher Aw

Answer 36

because bacteria grow and they will produce fungicides

Question 37

T or F : lowering the Aw will kill the microorganisms

Answer 37

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

Question 38

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

Answer 38

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

Question 39

How does the ionizing radiation works

Answer 39

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

Question 40

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

Answer 40

smaller

Question 41

What is the advantage of gamma radiation

Answer 41

•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

Question 42

What is redappertization?

Answer 42

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

Question 43

What is Radicidation?

Answer 43

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

Question 44

What is Radurization

Answer 44

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)

Question 45

What is HPP ?

Answer 45

•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)

Question 46

What is PEF?

Answer 46

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

Question 47

Does HPP kills spores

Answer 47

no

Question 48

Does PEF kills spores

Answer 48

no