Cold Storage Systems

Question 1

Can different produce be stored together?

Answer 1

Yes, mixed storage is common (separate is ideal but $$$)

need to consider compatibility!

Question 2

What is considered to be a simple storage system?

Answer 2

simple ventilated storage

regular atmosphere (with air circulation, ventilation, refrigeration, etc)

Question 3

What is considered to be a complex storage system? What is required?

Answer 3

hypobaric (low pressure) storage
CA storage

need insulation, airtight, vapor barrier, control temp/RH/air composition

Question 4

Guidelines for maintaining temperature:

Answer 4

prevent fluctuations (+/- 2C)
adequate refrigeration capacity

Question 5

What are the effects if refrigeration capacity is too low?

Answer 5

more fluctuation
warm produce
slow cooling

Question 6

Which is better, having many small refrigeration units or a single large one?

Answer 6

many small ones (fill efficiently)

Question 7

Why is it undesirable to have oversized refrigeration capacity?

Answer 7

wasteful ($$$)

Question 8

temperature fluctuation will cause:

Answer 8

loss of quality (dessication, sweating, condensation, warming, etc)

Question 9

What practices help improve refrigeration capacity? (5)

Answer 9

1. keep room temp close to fridge temp (less fluctuation)
2. large surface area for cooling
3. insulation to prevent heat entry/cold loss
4. good (moderate) air velocity
5. good temp control (thermostat)

Question 10

cooling systems should be kept at relatively high ____ to prevent severe dessication

Answer 10

RH

Question 11

What are some high humidity storage techniques?(3)

Answer 11

1. jacketed storage
2. filacell storage
3. fog spray

Question 12

How does jacketed storage work?

Answer 12

double outer wall, covered by insulation:

refrigerated air circulate in space outside storage chamber -> cools room without direct contact (no humidity loss)

Question 13

Jacketed storage is a way of offering temperature control without affecting ____

Answer 13

RH

Question 14

Jacketed storage is a ____ system, in order to trap ____ inside. What is also trapped inside, and what needs to be done to remove it?

Answer 14

closed
humidity (from produce)
need to remove CO2 from respiration; use bags of LIME

Question 15

What is a filacell storage system?

Answer 15

normal refrigeration system + HUMIDIFY air after leaving cooling coil -> humid air goes to produce (won’t dry it out)

Question 16

What is a fog spray system?

Answer 16

directly add mist/water spray into air stream

Question 17

Proper air velocity is essential for:

Answer 17

maintain cool temperature (heat transfer)
homogenous CA conditions (distribute gases)
prevent dessication (velocity can't be too high!)

Question 18

proper air velocity depends on: (3)

Answer 18

fans (type/capacity)
air delivery
stacking/package design

Question 19

In a regular atmosphere storage, you need to prevent buildup of ____ and _____, and depletion of ____.

Answer 19

CO2, ethylene

O2

Question 20

How is a CA/MA storage different from RA?

Answer 20

alter gas composition of air

-> 5% CO2, 2% O2, remove ethylene

Question 21

What is a common sealing (water vapor, air) material in storage systems?

Answer 21

polyurethane

Question 22

3 main types of storage systems:

Answer 22

1. ventilated
2. RA
3. CA

Question 23

benefits of CA storage: (5)

Answer 23

suppress respiration
less microbial activity
slower aging
less ethylene production/sensitivity

Question 24

disadvantages of CA storage:

Answer 24

may cause physiological disorders
irregular ripening
off flavors
may cause sprout/rooting

Question 25

What are good candidates for CA storage?

Answer 25

fruits: apple, peach, plum, kiwi, avocado, strawberry, banana, lime, etc

Question 26

What foods are bad for CA storage?

Answer 26

many vegetables: asparagus, broccoli, cauliflower, tomato, cabbage, corn, etc

Question 27

CA needs to accomplish 2 steps:

Answer 27

1. generate CA: remove O2/add CO2

2. maintain CA, ethylene removal, RH

Question 28

2 ways of generating CA:

Answer 28

passive (use natural respiration + membrane permeability)

active (use external source)

Question 29

Methods for CO2 addition/removal:

Answer 29

addition:
- CO2 cylinders

removal: (scrubbers): dissolve
- hydrated lime
- activated charcoal/molecular sieves
- water/brine

Question 30

How is oxygen removal accomplished: (2)

Answer 30

Recirculation method: take air out, remove O2, add back in
(open flame burner)

Purge method: add N -> flush O2 out

Question 31

True/False: O2 needs to be supplied during storage

Answer 31

True; need to prevent O2 depletion (need ventilation)

Question 32

At CA conditions, N gas is about ___%. What purpose does it serve?

Answer 32

92

acts as filler