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5) Post-Harvest > Lecture 8: Cold Storage Systems > Flashcards

Lecture 8: Cold Storage Systems Flashcards

1
Q

what components must be controlled in a storage system?

A 
temp
RH
air velocity
air composition
insulation
refrigeration capacity
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2
Q

simple systems are used for what?

A

ventilated storages (for potato, carrot, dry onion)

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3
Q

what do simple systems take into account?

A

insulation
air circulation
ventilation

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4
Q

simple systems uses what atmosphere storage?

A

RA storage = regular atmosphere storage

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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
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6
Q

what are examples of complex systems?

A

CA storage

hypobaric storage

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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

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8
Q

what should be used to estimate quality loss?

A

Q10 concept

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9
Q

temp fluctuations should be what?

why?

A

low +/- 2C

b/c large fluctuations means a loss of quality

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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

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11
Q

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

A
  • dessication if WVPD is positive

- condensation if WVPD is negative

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12
Q

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

A

normal and unexpected loads

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13
Q

how can storage life of incoming commodities be maximized?

A

by precooling incoming produce to storage temp

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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

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15
Q

if the refrigeration capacity is undersized, what occurs?

A
  • slow cooling
  • product warming
  • large temp fluctuations = larger quality loss
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16
Q

why should refrigeration capacity not be oversized?

A

more expensive

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17
Q

refrigeration temp should be close to _____

why?

A

room temp

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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?

A

fins

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
Q

describe the fog-spray system

A
  • direct addition of moisture to air stream

- can make use of sonication as well

26
Q

air circulation can be ___ or ___

which is more common?

A

natural or forced

forced is more common

27
Q

air circulation promotes what?

A
  • efficient heat and mass transfer
28
Q

is heat transfer desirable?

is mass transfer desireable?

A

yes

no

29
Q

air velocity is important for what?

A
  • maintaining proper temp

- establishing homogenous CA conditions

30
Q

proper air circulation depends on what?

A
  • fan type and capacity
  • air delivery
  • package design and stacking
31
Q

describe regular atmospheric systems

A
  • atmosphere not controlled
  • build up of CO2 and ethylene should be prevented
  • O2 depletion should be prevented
32
Q

what is CA? what is MA?

what is RA?

A

CA = controlled atmosphere

MA = modified atm

RA = regular atm

33
Q

describe CA/MA storage systems

A
  • altered atmosphere inside the storage chamber
  • lower O2 levels
  • higher CO2 levels
  • removal of ethylene (to slower ripening of produce)
34
Q

what are 2 types of RA?

A

jacketed storage

filacell system

35
Q

describe RA

A

insulated vapor proof structures with mechanical refrigeration units

36
Q

why are CA storage systems imp?

A

it can alter the gaseous environment inside the storage chamber

37
Q

what are desirable effects of CA storage?

A
  • lowered resp rate
  • slowed senescence
  • slowed ethylene production rate
  • lower fruit sensitivity to ethylene
  • alleviation of physiological disorders
  • suppressed pathogen activity
38
Q

what are undesirable effects of CA storage

A
  • can promote some physiological disorders
  • can induce irregular ripening
  • can favor development of off flavours
  • can favor stimulation of sprouting
39
Q

what are 2 imp aspects of CA/MA storage?

A
  1. CA generation: lowering O2 level, increasing CO2 level

2. CA maintenance: CO2, O2, ethylene removal, etc…

40
Q

what are 2 methods of CA generation?

A
  1. passive process: via produce respiration

2. active process: via external means

41
Q

what are 2 types of of O2 control systems?

A
  1. external gas generators: operates by open flame burners or catalytic converters
  2. N generators: gas or liquid N cylinders; Smit-oxydrain
42
Q

what is Smit-oxydrain?

A
  • Ammonia is converted to N
  • becomes N2 + H2
  • H2 combines with O2 to form H2O
  • N2 purges or replaces O2
43
Q

how does CA generation remove CO2?

A

by scrubbing systems

  • hydrated lime (absorbs lime)
  • water (solubilizes CO2)
  • brine water
  • activated carbon

5) Post-Harvest (17 decks)

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