Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Food Micro > Physical methods to preserve food > Flashcards

Physical methods to preserve food Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards
1
Q

Physical methods are the most common in food preservation: TRUE OR FALSE

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the 6 physical methods for food preservation?

A
  • High-temperature treatment (cooking)
  • Low-temperature preservation (freezing)
  • Decreasing water availability (drying, salting)
  • Ionizing irradiation
  • High-Pressure Processing (HPP)
  • Pulsed Electric Field (PEF)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens when the temperature exceeds the optimal temperature for an organism ?

A

Cell multiplication slows and eventually stops, additional temperature may result in cell death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Factors affecting heat transfer

A

1) Product Type: Liquids absorb heat faster than solid foods.
2) Container Material: Glass containers heat more slowly than metal containers
3) Container Shape: Tall and narrow containers heat more quickly than other shapes
4) Container Size: The center of small containers get reached more quickly than the center of large containers
5) Agitation: Agitation and mixing help to increase heat transfer especially in viscous or semi-viscous products
6) Temperature of Heating Medium: The greater the difference in temperature between the heat transfer medium and the product, the more rapid the rate of heat transfer to the product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do survivor plot depict ?

A

the logarithmic nature of population inactivation over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is decimal reduction time (D-value) ?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The D value of a microorganism (decreases/ increases) as the processing temperature increases?

A

decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

D value is plotted against temperature, it is known as a ___________, it is generally linear

A

thermal resistance plot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The ___________ represents the change in temperature required to change the D value of a microorganism by an order of magnitude (10-fold)

A

z -value, large z value indicates a more heat resistant organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The _______ is the time, in minutes, at a specified temperature, required to achieve a targeted reduction in a homogeneous population having a specific z value

A

F-value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

F-value is important in __________

A

the commercial canning industry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the key pathogen of concern for canned low acid foods

A

Clostridium botulinum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Sterilization vs commercial Sterilization

A

Sterilization: Sterilization is the process of rendering a product free of any living organisms

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

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
* Commercially sterile foods are heat treated just enough to produce a safe and shelf-stable product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Water can be bound by:

A
  • Hydroxyl groups
  • Carbonyl and amino groups of proteins
  • Salts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Formula for water activity

A

aw= P/P0

-For pure water, aw = 1.0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

aw is directly related to the equilibrium relative humidity (ERH) in the air surrounding the food:

A

ERH (%) = aw x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

High-moisture Foods

A

Foods with aw above 0.9, foodborne microbes can readily grow in these foods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Intermediate-moisture Foods

A

Foods with an aw 0.65-0.90, such as raisins or jam, because of the moderately low aw these foods are relatively resistant to microbial spoilage (think of how long a jar of jam will last in the fridge)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Dry foods

A

Foods with an aw < 0.65, such as milk powder or crackers, these foods do not support the growth of foodborne microorganisms and have a very long shelf life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What type of food is maple syrup

A

intermediate-moisture food

21
Q

How is maple syrup prepared?

A

by boiling the sap from sugar maple trees until the boiling temperature is 4.1C higher than that of pure water (which will vary based on air pressure but is around 100C)

22
Q

_________ has the lowest water requirements and can grow with an aw of >0.86. However, it cannot produce toxins at this level

A

Staphylococcus aureus

23
Q

Yeasts have higher or lower aw requirements compared to bacteria?

A

Lower

24
Q

_________ are xerotolerant and grow at lower moisture contents than the other types of spoilage microorganism

A

Molds

25
Q

Molds can produce __________, but ________ production is restricted under xerophilic conditions

A

Mycotoxins

26
Q

How does glycerol act as a humectant to lower aw ?

A

glycerol can permeate the bacterial membrane and may have a different inhibitory effect than that of sodium chloride or sucrose.

27
Q

What does Pulsed Electric field eliminate?

A

vegetative bacterial cells

28
Q

PEF processing is designed to treat what type of food?

A

pumpable food and involves the application of a short burst of high voltage to a product between two electrodes

29
Q

Drying

A

the process of mobilizing water present in a food matrix to its surface and then removing it from the surface by evaporation. It often involves simultaneous heat and mass transfer. Most drying operations involve converting liquid water in the material to vapor and then removing it by passing hot air over the product (i.e. beef jerky).

30
Q

Freeze-drying

A

During freeze-drying the product is frozen first and the moisture is removed via sublimation. Freeze-drying has a minimal impact on the structure and flavor of the food compared with other drying techniques, but has a relatively high cost, and is therefore used as a value added technique (i.e. camp dinners, instant coffee, infant formulas).

31
Q

Osmotic dehydration

A

is a procedure that involves removing water from fresh food using a hypertonic solutions (sucrose, salts, glycerol). It relies on the ability of the food cells to selectively permit the passage of water out of the food without allowing surrounding solutes to enter these cells. As a result food is dehydrated. It cannot remove all the moisture from the food, so it is mainly used as a pretreatment to other methods of dehydration. Primarily used for dehydrating fruits and vegetables (apples, blueberries, pineapples, mangoes etc.).

32
Q

Electromagnetic radiation with _______ wavelengths (gamma radiation) has lethal effects on microorganisms

A

shorter

33
Q

Longer wavelengths (microwaves) just generate _____ and are not as effective

A

heat

34
Q

Ionizing radiation includes _____ and _____ radiation

A

X Rays

gamma

35
Q

___________ is the primary target of ionizing radiation

A

The cell’s DNA

36
Q

the smaller the genome, the ______ the resistance to ionizing radiation

A

greater

37
Q

How is DNA caused in Ionizing Radiation?

A

By the reaction of reactive oxygen species that are generated during radiation

38
Q

How are X rays produced?

A

When an electron beam strikes a metal (tungsten or stainless steal)

39
Q

X-ray sources used to irradiate food are restricted to maximum energies of ______ or less, which is effective at treating fresh fruit and vegetables for microbial lethality

A

5MeV

40
Q

Drawback is that X-rays have ______________________

A

a high power requirement, and have a high requirement for cooling treatment (most of the energy is lost as heat)

41
Q

In gamma radiation, the radiation sources used for food are : (2)

A

cobalt-60 and cesium-137

42
Q

What are the advantages or gamma radiation?

A
  • high penetration power
  • energy is constant over the duration of the treatment
  • continuous source that doesn’t need to be turned off
43
Q

The process of gamma radiation usually consists of exposing

A

exposing the prepackaged food material to a radiation dose for a certain time

44
Q

Gamma radiation is emitted by:

A

an excited nucleus of a radioisotope, which permits the nucleus to go to its lowest energy or ground state

45
Q

Redappertization:

A

-involves a high dose (10-75 kGy) to produce commercial sterility

46
Q

Radicidation:

A

-involves medium dose (1-10 kGy) to produce the equivalent of pasteurization effect - effective against vegetative bacteria but spores are not inactivated

47
Q

Radurization:

A

-involves low dose irradiation (0.05-1.0 kGy) to control the presence of insects in grains or stop the sprouting of potatoes or fruit ripening

48
Q

HPP involves:

A

treating food with pressures in the range of 100-600 MPa which will inactivate most bacteria, yeasts, molds and viruses (spores survive)

Food Micro (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions