Special CA Systems

Question 1

What is a membrane CA system?

Answer 1

use gas diffusion through special membrane (selective permeability) -> achieve/maintain CA

Question 2

why is silicon elastamer a good membrane CA material?

Answer 2

5.5x permeability to CO2 vs O2

Question 3

The permeability ratio of CO2:O2 should be the inverse of: ____. Why?

Answer 3

inverse of concentration ratio

so that influx of O2 = efflux of CO2

Question 4

Why is it important for the influx/efflux of O2/CO2 important to be equal?

Answer 4

maintain CA

match respiration of produce

Question 5

What are important factors to consider for CA/MA storage?

Answer 5

• membrane permeability
• type of produce
• temperature
• effect of CA (slows respiration, changes conc. gradient)

Question 6

Diffusion unit systems developed in the 1960s (using CA)

Answer 6

Atmolysair

Marcellin

Question 7

In 1970, a method was developed for CA for ____ packaging, by using a ____ membrane with a silicon elastamer ____.

Answer 7

bulk
impermeable
window (for diffusion)

Question 8

What developments in CA tech were made in the 1980s?

Answer 8

polymers for packaging

include scrubbing agents (to remove bad compounds)

Question 9

Hypobaric storage and ____ are forms of ____. Produce is stored at very low ____, with continuous ____.

Answer 9

LPS; CA

pressure, continuous flow of saturated air

Question 10

What are the components of a hypobaric storage system? (6)

Answer 10

airtight chamber
vacuum pump
pressure regulator
flow regulator
humidifier/humidity control
refrigeration/temp control

Question 11

What are the typical conditions in hypobaric storage?
pressure:
RH:
temp:
air speed:

Answer 11

pressure: 1-50kPa
RH: 80-100%
temp: -15 to -2C
air speed: 3-4 air changes

Question 12

The lower the air pressure, the greater the ____. This will require a removal of _____, which will cause lowering of: _____.

Answer 12

volume
90% air from chamber
lower N, O2, CO2 concentration

Question 13

O2 concentration in a vacuum chamber will depend on:

Answer 13

pressure
RH
temperature (higher -> less O2)

Question 14

The higher the humidity in a vacuum chamber, the (higher/lower) the oxygen concentration

Answer 14

lower

Question 15

Lowering the pressure (increase vacuum) will (increase/decrease) diffusivity, which results in reduced _____

Answer 15

increase

concentration gradients

Question 16

Advantages of LPS (6)

Answer 16

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

Question 17

What are disadvantages and concerns with LPS?

Answer 17

need special structures ($$$)
lack of flavor in produce

leaks
implosions