Cold Storage Systems Flashcards
Can different produce be stored together?
Yes, mixed storage is common (separate is ideal but $$$)
need to consider compatibility!
What is considered to be a simple storage system?
simple ventilated storage
regular atmosphere (with air circulation, ventilation, refrigeration, etc)
What is considered to be a complex storage system? What is required?
hypobaric (low pressure) storage
CA storage
need insulation, airtight, vapor barrier, control temp/RH/air composition
Guidelines for maintaining temperature:
prevent fluctuations (+/- 2C) adequate refrigeration capacity
What are the effects if refrigeration capacity is too low?
more fluctuation
warm produce
slow cooling
Which is better, having many small refrigeration units or a single large one?
many small ones (fill efficiently)
Why is it undesirable to have oversized refrigeration capacity?
wasteful ($$$)
temperature fluctuation will cause:
loss of quality (dessication, sweating, condensation, warming, etc)
What practices help improve refrigeration capacity? (5)
- keep room temp close to fridge temp (less fluctuation)
- large surface area for cooling
- insulation to prevent heat entry/cold loss
- good (moderate) air velocity
- good temp control (thermostat)
cooling systems should be kept at relatively high ____ to prevent severe dessication
RH
What are some high humidity storage techniques?(3)
- jacketed storage
- filacell storage
- fog spray
How does jacketed storage work?
double outer wall, covered by insulation:
refrigerated air circulate in space outside storage chamber -> cools room without direct contact (no humidity loss)
Jacketed storage is a way of offering temperature control without affecting ____
RH
Jacketed storage is a ____ system, in order to trap ____ inside. What is also trapped inside, and what needs to be done to remove it?
closed
humidity (from produce)
need to remove CO2 from respiration; use bags of LIME
What is a filacell storage system?
normal refrigeration system + HUMIDIFY air after leaving cooling coil -> humid air goes to produce (won’t dry it out)
What is a fog spray system?
directly add mist/water spray into air stream
Proper air velocity is essential for:
maintain cool temperature (heat transfer) homogenous CA conditions (distribute gases) prevent dessication (velocity can't be too high!)
proper air velocity depends on: (3)
fans (type/capacity)
air delivery
stacking/package design
In a regular atmosphere storage, you need to prevent buildup of ____ and _____, and depletion of ____.
CO2, ethylene
O2
How is a CA/MA storage different from RA?
alter gas composition of air
-> 5% CO2, 2% O2, remove ethylene
What is a common sealing (water vapor, air) material in storage systems?
polyurethane
3 main types of storage systems:
- ventilated
- RA
- CA
benefits of CA storage: (5)
suppress respiration
less microbial activity
slower aging
less ethylene production/sensitivity
disadvantages of CA storage:
may cause physiological disorders
irregular ripening
off flavors
may cause sprout/rooting
What are good candidates for CA storage?
fruits: apple, peach, plum, kiwi, avocado, strawberry, banana, lime, etc
What foods are bad for CA storage?
many vegetables: asparagus, broccoli, cauliflower, tomato, cabbage, corn, etc
CA needs to accomplish 2 steps:
- generate CA: remove O2/add CO2
2. maintain CA, ethylene removal, RH
2 ways of generating CA:
passive (use natural respiration + membrane permeability)
active (use external source)
Methods for CO2 addition/removal:
addition:
- CO2 cylinders
removal: (scrubbers): dissolve
- hydrated lime
- activated charcoal/molecular sieves
- water/brine
How is oxygen removal accomplished: (2)
Recirculation method: take air out, remove O2, add back in
(open flame burner)
Purge method: add N -> flush O2 out
True/False: O2 needs to be supplied during storage
True; need to prevent O2 depletion (need ventilation)
At CA conditions, N gas is about ___%. What purpose does it serve?
92
acts as filler
