Brainscape's Knowledge GenomeTM

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


See full index

food processing > Novel techniques: electro-technologies > Flashcards

Novel techniques: electro-technologies Flashcards

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

Electro technologies for thermal processing include: (5)

A

MW, RF, ohmic, PEF, PL

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

MW are part of the _____ spectrum. They are (longer/shorter) waves, and can be generated by:

A

EM (electro-mag)
longer
oscillating electric fields

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

Why are frequencies used for MW restricted? Which ones are permitted?

A

interfere w/ radar communications

915MHz for INDUSTRIAL applications
2450MHz for DOMESTIC applications

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

The 3 factors that affect MW heating:

A
  • frequency
  • dielectric properties of food
  • thermo-physical properties of food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do MW induce heating in food? (2) (on molecular level)

A

oscillating field will cause electronic/dielectric heating:

  • dipole rotation - dipole molecules flip flop repeatedly
  • ionic polarization - vibration of ionic salts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True/False: MW used for domestic applications have longer wavelengths than industrial MW

A

False; higher frequency so shorter wavelength

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

diaelectric properties of foods are assessed by what 2 parameters?
What factors affect it?

A

dielectric constant - ability to ABSORB MW
loss factor - ability to DISSIPATE MW

depends on: temp, MW properties, product composition

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

What happens to penetration of MW as depth increases?

A

decrease exponentially

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

What are some applications of MW?

A 
heat/reheat
pasteurize/sterilize
cooking
temper/thaw
drying
enhance other processes: (extraction, osmotic drying, finnish drying, etc)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What affects penetration depth? (3)

A

frequency
state
dielectric constant

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

the higher the frequency, the (higher/lower) the penetration depth.
Higher penetration occurs for a (solid/liquid) state
The higher the dielectric constant, the (higher/lower) the penetration depth.

A

lower
solid
lower

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

What feature makes MW good for drying?

A

selective energy absorption by polar molecules (water is very polar)

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

What are the advantages of MW?

A 
volumetric heating (evenly heat)
faster
easy controls/clean up
targets polar molecules
can combine w/ other energy/chemicals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are some problems with MW? (4)

A

lack of penetration in large sample

uneven heating in heterogenous sample (or uneven field strength)

wet environment - no browning, no maillard, no crispness

measurement difficulties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Volumetric MW heating is only possible with: (2)

A

homogenous product: liquid or semisolid

uniform field strength

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

A major safety concern with MW heating is:

A

uneven heating: cool spots lead to inadequately processed/cooked food

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

What are the various temperature distribution studies done with MW?

A

frozen products
family size containers
hedge-hog system (when MW off)

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

What highly energy intensive step in vegetable processing can be replaced by MW? Why is this better? (4)

A

blanching

less affluent (water, steam)
effective on enzymes (enhanced!)
can air-cool afterwards
better quality

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

Why would microwave pasteurization give higher quality? (2)

A

do not require heated surface (heat food directly)
so no fouling (over heating of proteins/carbs)
= HIGHER QUALITY

can use lower temp

20
Q

How do MW kinetics compare to thermal kinetics?

A

equal, or enhanced (not conclusive)

21
Q

Aside from thermal effects, what else could possibly contribute to MW kinetics? (2)

A 
non-thermal (effects observed at lower temps)
enhanced thermal (effects at high temp that is GREATER than can be explained by just thermal alone)
22
Q

True/False: MW kinetics have an instant CUT.

A

False. Need to integrate.

23
Q

Experimentally, were any non-thermal effects found for MW?

A

No

24
Q

What property makes MW particularly useful for thawing

A

deep penetration of MW for ice

25
Q

What conditions are necessary for MW thawing and tempering?

A

thawing: low power (otherwise surface heat too fast)
tempering: in freezer room to keep frozen

26
Q

tempering is:

A

heating to close to zero degrees (not melted, but warmer)

27
Q

How does MW drying occur? What is an excellent version of this method?

A

heats water, evaporated -> picked up by air

vacuum MW drying: vacuum very good at picking up moisture

28
Q

What types of packaging material types are used for MW, and what are their properties? (3)

A
  • transparent: transmit MW to heat directly
  • reflective: completely protect from MW
  • receptor/susceptor: selectively absorb MW -> convert to IR -> create “oven” environment (crisping)
29
Q

an alternative to MW heating, with high penetration power

A

RF

30
Q

What are common frequencies used for RF?

A

13.56
27.12
40.68
(MHz)

31
Q

The major disadvantage of RF is:

A

high capital investment ($$$)

32
Q

True/False: RF has similar advantages as MW.

A

True, but with deeper penetration

33
Q

True/False: RF is widely used in the food industry

A

False; but used for snack foods, drying biscuits

34
Q

RF is mostly used for ____ purposes, while MW are mostly used for ____ uses

A

industrial

domestic

35
Q

The deeper penetration ability of ___ would make it a good candidate for:

A

RF; aseptic processing, continuous cooking (hams, sausage)

36
Q

How does ohmic heating work?

A

pass electric current through food to heat

37
Q

The higher the _____, the faster the heating rate

A

voltage

38
Q

ohmic heating rate is proportional to:

A

power
conductivity
voltage
salt content

39
Q

Would fresh or cured meat heat faster with ohmic heating? Why?

A

cured

higher salt content -> increase E conductivity

40
Q

Advantages of ohmic:

A 
quiet
fast
gentle process
easily tailored
better energy conservation
41
Q

main problem with ohmic heating:

How can this be addressed? (2)

A

corrosion of metals

common stainless steel easily corrode at 50-60Hz AC

can use titanium (but $$$)
or use HIGH FREQUENCY >1kHz (can use steel)

42
Q

A similar process to ohmic heating, but for liquids:

How does it differ?

A

pulsed electric field (PEF)

HIGHER voltage, SHORTER cycles

43
Q

PEF is good for inactivating: _____, but not ____.

A

microbes

spores

44
Q

PEF is poor for:

A

heterogenous liquid
air bubbles in liquid (reduce effect)
highly viscous liquid
food with electric conductivity

45
Q

What is PL?

A

pulsed light
short pulses of bright “white light”
20 000x intensity of normal light, last only fraction of second

46
Q

PL is effective for:____?

What is required? (2)

A

decontamination of food, package, surface

high intensity, access important volume/surfaces

food processing (17 decks)

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