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NUFS 100 > Lecture 7: Thermal processing > Flashcards

Lecture 7: Thermal processing Flashcards

1
Q

What is thermal processing?

A

Severe heat treatments; canning as well as-

mild heat treatments pasteurization and balancing.

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2
Q

What are the 3 goals of food preservation?

A
  1. Minimize food spoilage
  2. Maximize safety and stability
  3. Optimize nutritional value and acceptability
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3
Q

What was the origin of Thermal processing?

A

Nicolas Appert (1750-1841) was the first to establish industrial thermal processing of foods.

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4
Q

What was Louis Pasteur’s contribution to thermal processing?

A

(1822-1895)
Microbes spoil wine, beer, and milk.

Developed pasteurization.

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5
Q

Why is thermal processing a effective food preservation and sterilization technique?

A

Bacteria are susceptible to heat.

Additionally, enzymes and oxidative changes are also inhibited

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6
Q

What is canning?

A

Canning is a severe heat treatment.

Generally 110 - 121 C for 15min

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7
Q

How is canning achieved?

A

Achieved using retort?

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8
Q

What is the goal of canning?

A

the destruction of all pathogens.

Although some extremeophiles may still remain within the canned environment.

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9
Q

How long dose the average canned food product last?

A

A 2-year shelf-life is achieved.

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10
Q

What are the 3 factors to consider when establishing how much heat to apply during thermal processing?

A
  1. Type and size of container used
  2. Heat transfer ability of the food
  3. microbial heat reistance
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11
Q

What is conduction?

A

heat transferred from molecule to

molecule via molecular collisions

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12
Q

What is convection?

A

Heat transferred through a liquid which circulates.

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13
Q

What is the main consideration when heating up objects?

A

Heat must get to the “cold spot” in the can.

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14
Q

What is the difference between the molecular moment of conduction and convection?

A

Conduction: molecule to molecule in straight lines

Convection: molecules move in fluid motion.

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15
Q

Is there a size limit to the size of the can that can be thermally processed?

A

Yes there is.

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16
Q

What is the thermal death-time curve?

A

This curve provides data on the destruction of a specific microbe at different temperatures.

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17
Q

What is a D value?

A

Decimal reduction time

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18
Q

What is the D Value?

A

A unit used to describe the heat resistance of microbes.

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19
Q

What do D values represent?

A

D values represent the time needed to destroy 1 log cycle (90%) of the bacteria present.

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20
Q

What is an example of a D value?

A

D100 = 2 min

or

S. aureus D71.7 = 4.1 second

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21
Q

What are D values used for?

A

Used to calculate process time in the food industry.

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22
Q

How many Log cycle reductions are needed in the food industry?

A

12

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23
Q

What are two things to think about when determining what D value we should use?

A
  1. depends on the specific organisms present

2. Depends on the number of organisms present

24
Q

What is the standard target organism within the canning process?

A
  • Bacillus stearothermophilus for canned foods

* These spores are more heat resistant than C. Botulinum

25
Q

What is the probability that a can would have a botulinum spore within it?

A

1/1000000000000

26
Q

Bacteria are killed most easily within what environment?

A

High heat, and high acid conditions.

27
Q

Is the process of sterilization different in naturally acidic foods?

A

Lower temperatures and shorter times can be used.

28
Q

What are the danger zones?

A

4-60 C (lots of pathogen growth)

29
Q

What are examples of mild heat treatments?

A

Pasteurization and blanching.

30
Q

What are the aims of mild heat treatments?

A
  • Kill pathogens
  • Reduce bacterial count; food is not sterile
  • inactivate enzymes
31
Q

What are the advantages of mild heat treatments?

A

Minimal nutritional and palatability changes

32
Q

What are the disadvantages of mild heat treatment?

A

Short shelf life

additional processing method is required (refrigeration or freeing)

33
Q

What is pasteurization?

A

Used to process beverages and liquid

34
Q

What happens during pasteurization?

A

Pathogens are destroyed but some spoilage microbes will still remain.

35
Q

What happens to enzymes during pasteurization?

A

They becomes inactive

36
Q

What additional preservation methods are used to

enhance shelf life of pasteurised products?

A

refrigeration

37
Q

When is blanching used?

A

Used prior to freezing for vegetables and some fruit.

38
Q

What is the role of blanching?

A

Inactivates enzymes that would cause off-odours and offcolours during frozen storage.

39
Q

what is blanching?

A

Vegetables are immersed in boiling water for a few

minutes

40
Q

What is the result of blanching?

A

“reduces the microbial load”; does not create a

commercially sterile product

41
Q

How is radiation used to sterilize and preserve food?

A

Radiant energy comes from electromagnetic waves, microwaves are most common within this feild.

Water molecules in a food are excited by microwaves.

42
Q

What is the advantage of microwave perseration?

A

Microbes are killed at far lower temperatures than conventional processes?

43
Q

true or false:

Irradiation is a ____ process.

A

cold

44
Q

What type of radiation is used in radiant energy processing?

A

ionizing radiation.

45
Q

How common is the use of irradiation in the food industry?

A

it is limited to only some foods and specific purposes

46
Q

What is the purpose of irradiation?

A
  • pathogen destruction
  • Spoilage inhibition
  • longer shelf-life of fruits and vegetables by slowing ripening and sprouting.
47
Q

What is cold pasteurization?

A

an alternative to thermal
pasteurisation.
• High physical pressure for 5-20 minutes destroys
microbes

48
Q

are microb spores destroyed within cold pasteurization?

A

no

49
Q

What is the benefit of cold pasteurization?

A

Product nutritional and sensory properties are preserved.

50
Q

When would cold pasteurization work best?

A

Works best on high moisture products, not dry products or

those with air pockets.

51
Q

What is cold pasteurization a example of?

A

High Pressure Processing (HPP)

52
Q

What is HPP applied to?

A

HPP is applied to fresh juices, meats, prepared products.

53
Q

What is the focus of hurdle technology for food preservation?

A

Safe and fresher foods within minimal affect on the food quality.

54
Q

What is the method of application for hurdle technology for food preservation?

A

a series of preservative factors that the target
microorganisms are not able to overcome.

such as available water ,pH, temp, and chemical antimicrobials

55
Q

How are Hurdles applied?

A

The combination of hurdles are chosen specifically for each food.

56
Q

Are all hurdles applied at the same level?

A

Individual hurdles may be set at lower concentrations/intensities
than would be required if only a single hurdle was used as the
preservation technique.

NUFS 100 (10 decks)

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