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FDSC200 > Week11C1-2 : thermal processing > Flashcards

Week11C1-2 : thermal processing Flashcards

1
Q

What are the three basic levels of heat treatment?

A
  1. Sterilization
  2. commercial sterility
  3. Pasteurization/blanching
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2
Q

What is the temperature of sterility and the time

A

121˚C for 15 minutes.

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3
Q

What is the definition of sterility?

A

means there is no living forms alive or biologically active

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4
Q

What is the definition of commercial sterility ?

A

kill all pathogenic and toxin-forming vegetative organisms.

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5
Q

at what temperature is steam if under these pressure :
10 psi :
15 psi :
20 psi :

A

10 psi : 116
15 psi : 121
20 psi : 127

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6
Q

T or F : for low acid foods, the temperature of the food needs to reach temperature higher than 100C

A

t

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7
Q

T or F : the temperature used in pasteurization are over the boiling point

A

f

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8
Q

T or F : the pasteurization and the commercial sterility deactivate spores

A

false, the pasteurization doesn’t deactivate spores but the commercial sterility does

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9
Q

What is the goal of blanching

A

To denature the enzymes that are deleterious in fruits and vegetables

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10
Q

What are the three rules that decides the thermal processing that will be done?

A
  1. eliminating the microorganisms
  2. Maintaining the nutritional and sensory qualities
  3. Food safety
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11
Q

T or F : C. Botulinum is used to evaluate the efficacy of a thermal processes

A

F, it is too dangerous because it is a dangerous spore and you need to use the more temperature resistant spores

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12
Q

What are the two spore former used to evaluate the efficacy of thermal processing

A
  1. Clostridium sporogenes PA3679

2. Bacillus stearothermophilus

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13
Q

What is the commercial sterility levels of spores in cans

A

10^-6 (or 12 log reduction or 12D)

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14
Q

What is the D-value?

A

the deciml reduction time is the heating time required at a given temperature to reduce the microbial population by one log unit.

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15
Q

How is the D-value determined

A

by experimentation of standard plate count of samples that have been heated for different amounts of time

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16
Q

What is the thermal death rate curve?

A

The curve that shows the log reduction of spores against the time for a specific temperature

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17
Q

Does temperature affect the thermal death curve?

A

yes.

18
Q

What is the Z value?

A

It is the thermal resistance of an organisms and depends on the d-value. The temperature increase corresponding to reduce the D value by one loge or 10 factor

19
Q

What does HTST stands for ?

A

high temperature short time

20
Q

What are the two types of thermal processing?

A
  1. conventional processing

2. Aseptic processing

21
Q

What is the type of thermal processing that is suitable for the HTST processes

A

aseptic processing

22
Q

What is the name of the machine used that is a large pressure cooker

A

batch retort.

23
Q

T or F : the thermal processing using a batch retort is a continuous process

A

f

24
Q

What is the name of the machine that is u-shaped and used in the conventional thermal processing for canning

A

hydrostatic cooker and cooler

25
Q

T or F : the hold time of the thermal processing takes into account only the D-value

A

False, it needs to take into account the come-up and come-down times.

26
Q

Where are placed the thermocouples that measure the product heat

A

at the cold point

27
Q

What factor influence the location of the cold point in food?

A

it depends on the type of heat transfer that is predominant in the food. For solids it is conduction and for liquids it is convection

28
Q

Complete : for conduction in heat penetration studies, the cold point will be at ___ of the can

A

center

29
Q

Complete : for convection in heat penetration studies, the cold point will be at ___ of the can

A

1/3 up from the bottom

30
Q

T or F : heat tranfer characteristics can change during the thermal processing

A

true, example for gelatinization will slow down the rate of heat transfer.

31
Q

What is the temperature of pasteurization of milk in the HTST ?

A

71C for 15 seconds then rapid cooling at 2C

32
Q

What is the temperature for UHT in milk pasteurization?

A

over 100C for 1 second

33
Q

What is the commonly used method for pasteurization of milk ?

A

HTST pasteurization with plate heat exchangers.

34
Q

When was developed the UHT processing

A

1970

35
Q

Since what year do we use the HTST pasteurization

A

1930

36
Q

What are the three advantages of aseptic processes?

A
  1. continuous
  2. Very high and efficient heat transfer rates
  3. Not constrained by the container size and shape
37
Q

What are commonly used to sterilize the packaging in the asceptic processing

A

UV light and hydrogen peroxide

38
Q

What is the temperature and time of batch processing

A

62,5 for 30 minutes

39
Q

How does heat kill the microorganisms?

A

by denaturing the proteins and inactivating their enzymes.

40
Q

T or F : the asceptic processing is useful for heat sensitive products.

A

True, owing to HTST.

41
Q

What is the temperature and time used for commercial sterility?

A

Depends on the product, but the time should result in a 12log reduction of the microbial load and that depends on the temperature.

FDSC200 (23 decks)

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