Lecture 8: Cold Storage Systems Flashcards

(43 cards)

1
Q

what components must be controlled in a storage system?

A
temp
RH
air velocity
air composition
insulation
refrigeration capacity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

simple systems are used for what?

A

ventilated storages (for potato, carrot, dry onion)

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

what do simple systems take into account?

A

insulation
air circulation
ventilation

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

simple systems uses what atmosphere storage?

A

RA storage = regular atmosphere storage

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

what needs to be taken into account for complex systems?

A
insulation
air tightness
vapor barrier
price control of temp
RH
air comp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are examples of complex systems?

A

CA storage

hypobaric storage

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

separate storage chambers for each produce is ideal but not practical. What is more common instead? What must be taken into account?

A
  • mixed loads

- compatibility of temp, ethylene, RH, odor

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

what should be used to estimate quality loss?

A

Q10 concept

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

temp fluctuations should be what?

why?

A

low +/- 2C

b/c large fluctuations means a loss of quality

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

warm produce coming in contact with cold air results in what?

A
  • dessication, if air is not saturated

- produce sweating, if air is saturated

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

warm air coming in contact with cold produce results in what?

A
  • dessication if WVPD is positive

- condensation if WVPD is negative

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

adequate refrigeration capacity should be able to handle ____ and ___ loads

A

normal and unexpected loads

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

how can storage life of incoming commodities be maximized?

A

by precooling incoming produce to storage temp

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

storage life of all commodities will be at risk when….?

A

warm products are brought in. This causes large temp fluctuations and product warming

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

if the refrigeration capacity is undersized, what occurs?

A
  • slow cooling
  • product warming
  • large temp fluctuations = larger quality loss
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

why should refrigeration capacity not be oversized?

A

more expensive

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

refrigeration temp should be close to _____

why?

A

room temp

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

what kind of cooling surface area of cooling coils is best?

A

larger surface area = more efficient heat transfer

19
Q

what can be used to increase surface area?

20
Q

why is good air velocity important?

A

for proper temp distribution

at high flow rate, dessication occurs

at low flow rates, improper cooling occurs

thus, moderate rate is the best

21
Q

why is adequate thermal insulation imp?

A

prevents heat gain from walls, doors, floor, etc…

22
Q

how can moisture loss be reduced?

A
  • having a smaller temp diff between coil and air
  • smaller temp fluctuation
  • humidifying air externally using special technique for storage: jacketed storage, filacell storage, fog spray system
23
Q

describe the jacketed storage system

A

conserves moisture to better deal with high RH

24
Q

describe the filacell storage system

A

humidifies air leaving cooling coil

25
describe the fog-spray system
- direct addition of moisture to air stream | - can make use of sonication as well
26
air circulation can be ___ or ___ which is more common?
natural or forced forced is more common
27
air circulation promotes what?
- efficient heat and mass transfer
28
is heat transfer desirable? is mass transfer desireable?
yes | no
29
air velocity is important for what?
- maintaining proper temp | - establishing homogenous CA conditions
30
proper air circulation depends on what?
- fan type and capacity - air delivery - package design and stacking
31
describe regular atmospheric systems
- atmosphere not controlled - build up of CO2 and ethylene should be prevented - O2 depletion should be prevented
32
what is CA? what is MA? | what is RA?
CA = controlled atmosphere MA = modified atm RA = regular atm
33
describe CA/MA storage systems
- altered atmosphere inside the storage chamber - lower O2 levels - higher CO2 levels - removal of ethylene (to slower ripening of produce)
34
what are 2 types of RA?
jacketed storage | filacell system
35
describe RA
insulated vapor proof structures with mechanical refrigeration units
36
why are CA storage systems imp?
it can alter the gaseous environment inside the storage chamber
37
what are desirable effects of CA storage?
- lowered resp rate - slowed senescence - slowed ethylene production rate - lower fruit sensitivity to ethylene - alleviation of physiological disorders - suppressed pathogen activity
38
what are undesirable effects of CA storage
- can promote some physiological disorders - can induce irregular ripening - can favor development of off flavours - can favor stimulation of sprouting
39
what are 2 imp aspects of CA/MA storage?
1. CA generation: lowering O2 level, increasing CO2 level | 2. CA maintenance: CO2, O2, ethylene removal, etc...
40
what are 2 methods of CA generation?
1. passive process: via produce respiration | 2. active process: via external means
41
what are 2 types of of O2 control systems?
1. external gas generators: operates by open flame burners or catalytic converters 2. N generators: gas or liquid N cylinders; Smit-oxydrain
42
what is Smit-oxydrain?
- Ammonia is converted to N - becomes N2 + H2 - H2 combines with O2 to form H2O - N2 purges or replaces O2
43
how does CA generation remove CO2?
by scrubbing systems - hydrated lime (absorbs lime) - water (solubilizes CO2) - brine water - activated carbon