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Food Microbiology > Industrial toolkit 2 > Flashcards

Industrial toolkit 2 Flashcards

ANtimicrobials and non-thermal processes

1
Q

Non-thermal processes include?

A

irradiation, Pulsed electric fields and high hydrostatic pressure

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2
Q

Bacteriaiophage as a processing aid.. a little bit about them.
tip: considered organic

A 
Virus bacteria 
most abundant organisms
- very specific target
NO impact on food quality (not spoilage organism!)
use 10^8 PFU = 3 log kill. 
- Phage must contact bacterial cell
- dependent on food.
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3
Q

What is bacteriophages used to control in RTE meats?

A

L. monocytogenes

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4
Q

Irradiation

A

Used especially in microwaves to excite water molecule to heat up food.
high energy, shorter wavelength

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5
Q

Microwaves (non-ionizing)

A

Power source is cavity magnetron which dielectric heating and oscillation of water molecules.

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6
Q

Microwaves as thermal treatment

A

requires water.
pro’s: rapid, borad spectrum of actvity (viruses, mold, yeast, bacteria)
con: thermoydnaimic gradients ( distribution of water not always uniform), dependent on Aw, endospores not killed.

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7
Q

Ultraviolet Radiation ( non-ionizing)

A

Power source: UV lamp
DNA absorbs UV.
causes DNA damage,
Affect depends on intensity and time.

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8
Q

What is resistant to UV radiation?

A

Gram negative< gram positive and yeast < endospores < mold spores «&laquo_space;viruses
The ability of these to recover is reverse.

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9
Q

What is hte pro and con of UV radiation?

A

Con:limited penetration (smooth surface), and pro is surfaces of foods and clear juices.

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10
Q

Ionizing radiation what is it?

A

Ejecting e- out of compound ( removes e- from atom to form ions)
- Distribution of atomic nucleus requred to be radioactive.
Uses x-rays, gamma rays, beta-particles
high frequency, high energy radiation

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11
Q

what is the positives of using ionizing radiation?

A

Control and near-sterility of bacteria, yeasts, moulds, endospores and viruses.

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12
Q

What are the three forms of ionizing radiation used?

A

B-particles, x-rays, gamma rays

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13
Q

Describe b-particles

A

High energy e-, stream of electrons emitted, little control on dosage, and some concern about radioactive food.

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14
Q

describe x-rays

A

produced from high voltage equiptment

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15
Q

Describe gamma rays

A

radioactive source C0^60 or Cs^137,

Cheapest form, uses atomic waste product, dispoal issues and can use electron beam accelerators.

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16
Q

Three forms of processes of ionization radiation.

A
  1. Radurization
  2. Radicidation
  3. Radappertization
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17
Q

Describe Radurization

A

Lose dose, considered soft pastuerization, QUALITY enhancement, and reduces spoilage orgnisms

18
Q

Describe Radicidation

A

Equivalent to pasteurixation, specifically refers to REDUCTION of pathogens.

19
Q

Describe Radappertization

A

Equivalent to sterilization, much higher dose, and not applied to food ( everything dead!)

20
Q

Cons of ionizing radiation

A

consumer resistance–> radioactive food.
dispoal of radioiostopes, SIDE EFFECTS: lipid oxidation (rancidity) (as increase dose, increase problem).
- Some food can be frozen prior to irradiation to inhibit sensory property changes.

21
Q

What doses of irradiation do you use on fresh foods vs. frozen?

A

fresh: 1.5-4.5Kgy
frozen: 2-7 kGy

22
Q

What is cold pasteurization?

A

Use electron beam. (same outcome as gamma irradiation)

  • limited ability to penetrate surface.
    3. 5cm in water, and products such as meat must be thin.
23
Q

Cold pasteurization effects on microorganisms

A

Product and dose dependent.
3 -6 log reudcition in E. coli O157:H7 in beef.
Reduction of other pathogens.
Salmonella spp., Yersinia enterocolitica, Campylobacter.
LITTLE IMPACT on spore-forming bacteria.

24
Q

Economic benifit?

A

Reduction in public health costs associated with foodborne diseases.
- Decrease cost in waste reduction and lawyers.
extends storage life.

25
Q

Labeling requirements

A

Written statement requ9ired and international symbrol required.

26
Q

PEF Pulse Electric Field technology

A

Apply current. (short, high-voltage purses of electricty) that causes cellular distribution.
Maintains aroma, taste and apperance.

NON-thermal.

27
Q

PEF processing applications

A

Microbial inactivation, enhance dryng and brining injection (reduces Aw)

28
Q

How does PEF work?

A

High voltage–> breaks cell membranes.
expand existing pores (form new pores too) Cells become permeable to small molecules which causes swelling and rupture= death.

29
Q

Is pore formation reversible?

A

Sometimes. Depends on:

  1. Electric field intensity
  2. Pulse duration and frequency
  3. Conductivity of samples ( Aw, ionic strength, pH)
30
Q

Microorganisms vulnerable to PEF?

A

Metabolically active membranes ( water on both sides to facilitate ion movement)
- bacteria, molds, yeasts
Not so affective on spores and virsuses. Hurdles present.

31
Q

Advantage of PEF?

A

Keeps product quality
uniform, no gradients of voltage within a product,
heating enhances antimicrobial affects.
Pore-forming compounds enhance antimicrobial affects.

32
Q

Disadvantages of PEF?

A

Membranes, low Aw has protective effect.
Liquid to semi-luid foods (meat, eggs, juices, milk, soup),
Anything with a high Aw can be used though.

33
Q

HHP or high hydrostatic pressure

A

Add pressure. Compression of a substance.
100-1000MPa
Achieve favorable thermodynamic changes.

34
Q

HPP processing applications

A 
Increase food quality
- microbial inactivation 
- texture and protein modification
- phase transitions
HPP alters thermodynamic properties unlike PEF.
35
Q

HHP in foods

A

Compression of molecule will heat it up. it is a non-thermal process though.
- Used in cheese production, jam.

36
Q

How does HHP work?

A

Compression of a sample (decrease volume) Causes heating (adiabatic heating)
NON-THERMAL TREATMENT.
molecular rearragement and folding occurs.
- dissociation reactions occur,
- water very important. (small crystal- less destruction.)

37
Q

What pressure stops growth?

A

Usuually around 50MPa’s.

38
Q

Protein denaturation in pressure and heat

A

heat: Increae heat, new covalent bonds form, protein denature and it’s cheap.
Pressure: no new covalent bonds, expensive, rearrangement of molecules dissociation of proteins. loss of protein secondary, and irrversible protein denaturation.

39
Q

Microorganisms vulnerable to HHP

A

without heating:
Vegetative bacteria, fungal and mold spores, and viruses.

With heating:
Bacterial endospores : C. spp and Bacillus spp.

40
Q

Advantages of HHP?

A

Maintain quality of product, low energy vost vs. heat,
Uniform,
Heat enhances effect,

41
Q

Disadvantages of HPP

A

Some resistant strain of bacterial endospores

Food Microbiology (13 decks)

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