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Post harvest technology > Irradiation principles > Flashcards

Irradiation principles Flashcards

1
Q

Various applications of irradiation:

What is the main purpose?

A 
medical supplies
foods
cosmetics, sanitary products
pharmaceuticals
lab supplies
waste

main purpose: STERILIZATION

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2
Q

Advantage of radiation sterilization vs conventional methods:

A 
more energy efficient (don't need heating/cooling)
faster
don't need to be heat stable
no added chemicals
produce remains in "fresh" state
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3
Q

Canada is the largest supplier of ______, but the process is not approved in Canada so there are no commercial facilities.

A

irradiation equipment

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4
Q

True/False: there is no irradiated food or products available in Canada

A

False; imported goods (some approved)

industrial, government, university facilities exist

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5
Q

2 types of irradiation technologies:

A

man-made radio isotopes

electron accelerators

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6
Q

advantages of electron accelerators:

A

lower cost

easier to operate

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7
Q

What are labelling requirements for irradiated food?

A

if >10% ingredients have been irradiated, must display international irradiated symbol

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8
Q

1 Gray = ___ rad

A

100

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9
Q

What ranged of radiation dose is lethal to humans?

A

10^2 - 10^3 rad

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10
Q

True/False: the level of radiation needed to inhibit sprouting, kill insects, and sterilize is not high enough to harm humans

A

False!

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11
Q

Purposes of irradiation in food:

A

sterilize
kill insects/eggs
inhibit sprouting
overall increase shelf life

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12
Q

If the level of irradiation is below _____, it is not necessary to declare it. Is this lower radiation level still useful?

A

below 1 kGy
Can kill some microbes (pathogens)
but not enough to kill insects, or sterilize

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13
Q

Instrument used for measuring amount of radiation:

What is it based on?

A

dosimeter

radiation based on a aqueous chemical

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14
Q

Gamma rays interact mainly with: _____ to produce:_____. What is the consequence of this?

A

water molecules; make hydroxyl + free radicals

react with O2 to make more free radicals
cause chain reaction (react with proteins, carbs, fats)

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15
Q

Types of radiation:

A 
microwaves
gamma rays
infrared
solar
x-rays 
nuclear
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16
Q

the visible spectrum is what range?

A

400-700nm

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17
Q

large wavelength means (high/low) frequency

A

low

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18
Q

high energy rays will have ___ wavelengths and ___ frequencies. What are examples of high energy waves?

A

short; high

gamma rays, x rays

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19
Q

gamma rays and x rays are classified as:

Why?

A

ionizing rays

can knock off electron upon contact, makes an ion

20
Q

units for frequency, wavelength, and energy?

A

frequency: v (cycles/s)
wavelength: lambda (cm)
energy: E (eV)

21
Q

Which types of radiation are used for irradiating food?

A

gamma rays, x rays (ionizing)

22
Q

What are the forms of radiation waves and how are they produced?

A

alpha rays, beta rays, gamma rays

come from radioactive source + strong magnetic field

23
Q

How do the types of radiation waves differ?

A

alpha: weak penetration, low energy, +
beta: medium penetration, medium energy, -
gamma: high penetration, high energy, neutral

24
Q

What types of material are sufficient to stop the different radiation wave types?

A

alpha: sheet of paper
beta: aluminum
gamma: thick lead

25
Q

Beta rays are essentially a stream of: ____. Do they have practical use in irradiation?

A

high velocity electrons

yes; but need to accelerate (cyclotron or linear accelerator) to acquire enough energy to be useful

26
Q

radiation applications in the 1920s-1940s:

A

medical, treat cancer, x-ray tube

27
Q

radiation applications in 1940s-50s:

A

medical research, radiology equipment, diagnosis

28
Q

radiation applications in 1950s-60s:

A

Cobalt 60, Cesium 138, medical/dental applications, non-food sterilization

29
Q

radiation applications in 1960s-70s:

A

food research applications, industrial irradiators, other industrial applications (ex: polymer cross-linking)

30
Q

Radiation applications in 70s-80s-current:

A

small + large scale, wide applications, approved for food

31
Q

When was radiation first used for sterilization?

A

1950s-60s (non-food)

32
Q

When was radiation first used for food?

A

1960s-70s (research began)

33
Q

the primary source for gamma rays is: ____, which is an isotope of ____.

A

cobalt 60

cobalt 59

34
Q

a secondary source for gamma rays is: _____. Where is it sourced from?

A

Cesium 137

spent fuel from nuclear reactors (from uranium)

35
Q

What is a CANDU reactor?

A

Canada Deuterium Uranium reactor

pressurized heavy water reactor for generating power

36
Q

Cobalt 60 is formed by:

A

adding neutron to Cobalt 59

37
Q

what is the principle behind how ionization through radiation occurs?

A

The Compton effect: high energy gamma ray -> hits electron -> leaves as low energy ray
electron is rebounded, leaves atom -> creates ion

38
Q

What happens after all the radioactive energy is spent?

A

Return to ground state (no longer radioactive)
Co60 becomes Ni60
Cs137 becomes Ba137

39
Q

Co60 has a greater ____ than Cs137.

Cs137 has a greater ____ than Co60.

A

activity

lifespan (half-life)

40
Q

The parts of a CANDU process:

A 
slug
element
pencil
module
source rack
41
Q

describe a radiation facility:

A

heavily insulated room with radiation source
automatic controls bring food in -> irradiated -> out
when personnel need to enter, radiation source is lowered below ground in insulated, water-filled chamber

42
Q

Why is a conveyor system essential to food irradiation?

A

prevent humans from entering radioactive zone

43
Q

Radiation is described in terms of:

A

Dose: amount of radiation given/absorbed
intensity: rate at which dose is given

44
Q

Units for dose and intensity:

A

Dose: Rad or Gray (1Gy = 1J/kg)
Intensity: Curie (3.7*10^10 disintegration/s)

45
Q

How do radioisotopes differ from conventional energy sources?

A

constant; can’t turn off

radioactive decay - intensity decreases with time

46
Q

Rate of decay is proportional to

A

intensity

47
Q

what is the half-life?

A

time needed for intensity to be decreased by 50%

Post harvest technology (18 decks)

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