Special CA Systems Flashcards
What is a membrane CA system?
use gas diffusion through special membrane (selective permeability) -> achieve/maintain CA
why is silicon elastamer a good membrane CA material?
5.5x permeability to CO2 vs O2
The permeability ratio of CO2:O2 should be the inverse of: ____. Why?
inverse of concentration ratio
so that influx of O2 = efflux of CO2
Why is it important for the influx/efflux of O2/CO2 important to be equal?
maintain CA
match respiration of produce
What are important factors to consider for CA/MA storage?
- membrane permeability
- type of produce
- temperature
- effect of CA (slows respiration, changes conc. gradient)
Diffusion unit systems developed in the 1960s (using CA)
Atmolysair
Marcellin
In 1970, a method was developed for CA for ____ packaging, by using a ____ membrane with a silicon elastamer ____.
bulk
impermeable
window (for diffusion)
What developments in CA tech were made in the 1980s?
polymers for packaging
include scrubbing agents (to remove bad compounds)
Hypobaric storage and ____ are forms of ____. Produce is stored at very low ____, with continuous ____.
LPS; CA
pressure, continuous flow of saturated air
What are the components of a hypobaric storage system? (6)
airtight chamber vacuum pump pressure regulator flow regulator humidifier/humidity control refrigeration/temp control
What are the typical conditions in hypobaric storage? pressure: RH: temp: air speed:
pressure: 1-50kPa
RH: 80-100%
temp: -15 to -2C
air speed: 3-4 air changes
The lower the air pressure, the greater the ____. This will require a removal of _____, which will cause lowering of: _____.
volume
90% air from chamber
lower N, O2, CO2 concentration
O2 concentration in a vacuum chamber will depend on:
pressure
RH
temperature (higher -> less O2)
The higher the humidity in a vacuum chamber, the (higher/lower) the oxygen concentration
lower
Lowering the pressure (increase vacuum) will (increase/decrease) diffusivity, which results in reduced _____
increase
concentration gradients
Advantages of LPS (6)
low respiration heat + indirect heat removal reduced atmospheric composition increased diffusivity lower concentration gradients allow outward diffusion of other gases good control of O2 levels
What are disadvantages and concerns with LPS?
need special structures ($$$)
lack of flavor in produce
leaks
implosions