1) Various equipment is used in controlled atmosphere storage including CO2 scrubbers, O2 scrubbers, control systems, gas analysis equipment, Palliflex units, ethylene decomposers, cold store accessories, and humidification systems. 2) Biochemical changes occur in fruits and vegetables during controlled atmosphere storage including changes in flavor, development of off-flavors, volatile compounds, acidity, nutrition, ascorbic acid, lycopene, and phenolics. 3) Controlled atmosphere storage has been shown to generally maintain better flavor compared to air storage, though the fruit maturity at harvest also impacts flavor. Off-flavors can develop from increased ethanol and acetal

1. Equipments and Accessories used in
Controlled Atmosphere Storage and its
Biochemical Changes
Presented
By
Shyamala.C
2014604605
I-M.Tech (Storage Engineering)

2. Equipments Used
•CO2 scrubbers
•O2 scrubbers
•Control systems
•Gas analysis
•Palliflex
•Ethylene decomposers
•Cold store accessories
•Humidification
•Gas-tight doors

3. CO2 scrubbers
CO2-scrubbers
• Fruit ‘breathes’: it uses oxygen (O2) and produces
carbon dioxide (CO2).
• A CO2 scrubber removes the carbon dioxide (also
referred to as carbonic acid) that forms from
storage cells in order to prevent concentrations
getting too high and causing damage to the fruit.
Determining the capacity of the CO2-scrubber
In order to determine which CO2 scrubber is suitable
for your situation, the following must be considered;
• number of cool cells;
• cool cell dimensions;
• type & quantity of product in the cool cell (how
much CO2 does it produce);
• preferred storage conditions for CO2 in the cell;

4. Models CO2 scrubbers
• This model can supply a range of standard CO2-
scrubbers with capacities of 50 to 900 kg per 24 hour
period (at 3% CO2).
The advantages of CO2-scrubbers;
• one-tank system (instead of two-tank systems from
other suppliers)
1) cheaper to buy
2) twice as energy-efficient
3) 20% quicker
• unique system of sieve and distribution plates
A unique system of sieve and distribution plates enable
CO2 scrubbers to be up to 30% more efficient.
• minimal oxygen addition via the lung system
This lung (buffer) system ensures there is minimal
addition of O2 during the removal of CO2.

5. O2-scrubbers
• Fruit ‘breathes’: it uses oxygen (O2) and
produces carbon dioxide (CO2).
• An O2-scrubber reduces the oxygen level in
the storage area after the moment of storage
or after the interim opening of the cell, in
order to inhibit respiration and extend the
storage period.
Determining the capacity of the O2-scrubber
In order to determine which O2 scrubber is
suitable for the situation, the following must be
considered;
• number of cold stores;
• cool cell dimensions;
• type & quantity of product in the cool cell
• preferred storage conditions;
• speed of storage (how long it takes to load a
cool cell)

6. Models O2 scrubbers
• This model has a wide range of standard O2-
scrubbers with capacities from 7 to 145 kg per 24
hour period (at 1% O2).
There are two types of O2-scrubbers;
• VPSA O2-scrubber
• PSA O2-scrubber

7. VPSA O2 scrubbers
• VPSA technology (Vacuum Pressure Swing Absorption) is based
on an energy-efficient, low pressure technique.
• A VPSA can both circulate and inject. During circulation, the
residual oxygen level reduces along with the oxygen in the
storage cell.
• Circulation is the most energy efficient mode for lowering the
oxygen level in a storage area. So-called pull-down time is an
indication of the time necessary for circulation to bring your
storage cells to the required oxygen levels.
• During circulation, the VPSA reduces the oxygen concentration
in the cell up to 30% quicker than when injecting.
• The advantage of injection is that a cell can be kept at slight
over-pressure so that ULO conditions (ultra low oxygen, <3%)
are even possible in a storage area with a minor leak. With the
VPSA, you can switch between injecting and circulating and
vice versa at any given moment.

8. Advantages of VPSA O2-
scrubbers;
• The oil-free blower used in
VPSAs ensures that the active
carbon is not contaminated by
residual oil, resulting in its life-
expectancy more than doubling.
• Furthermore, the active carbon
filter is cleaned by means of a
vacuum technique, allowing it
to remain free of dirt and
moisture. This makes VPSA O2-
scrubbers the most durable and
energy-efficient

9. PSA O2 scrubbers
PSA O2-scrubber
• PSA stands for Pressure Swing Absorption, that
require a great deal of nitrogen which must be
supplied at high pressure.
• This involves cool houses with many (>20) cool cells
or cool houses in which oxygen removal takes place in
multiple cells simultaneously. This concerns volumes
greater than 85 m3 h-1.
• A PSA is suitable for making very pure nitrogen. Can
supply PSAs with a residual oxygen value of <0.1%
and volumes up to 1,200 m3 h-1.
Advantages of PSA O2-scrubbers;
• higher pressure (large Palliflex systems or tight pipes,
<50 mm)
• high purity (< 0.5% residual oxygen)
• large volumes (>85 m3h-1)

10. Control System
Operating system
• Operating systems form the heart of the
CA / ULO system.They regulate all of the
processes that guarantee accurate CA /
ULO conditions in cool cells or Palliflex
units.
• In addition, operating systems can
measure and regulate a number of other
processes such as humidity balance,
ethylene levels and temperature.In the
more compact CA / ULO systems, the
operating unit is placed in the front of the
scrubber.This involves an Auto-ULO-
Operating unit or a standard scrubber
unit.
• A central operating system comprises a
separate cabinet and uses measurement
hoses.

11. Operating systems for regulating;
• O2
• CO2
• Ethylene (measurement and removal)
• Temperature (from temperature registration to
complete cool operation)
• Moisture balance (RH, moisture loss,
humidification)

12. Gas analysis
• VA supplies a range of equipment for analysing gases
such as O2 and CO2 metres. Combination metres are
fitted into operating systems as standard.
In-built meters offer 3 types of oxygen measurement
methods;
i. galvanic cell (electro-chemical measurement cell);
suitable for measuring relatively low CO2 levels.
This is replaced every 2 years, on average (relatively
low cost). Often used for hard fruit and kiwi
storage.
ii. Zirconium cell; suitable for measuring higher CO2
values but not suitable for measuring high ethylene
concentrations. Replaced every 5 years on average.
Often used for berry storage.
iii. Paramagnetic cell; used infrequently due to higher
costs. Is very stable once installed but often
encounters problems during transport. Can
measure very accurately. Often used within
laboratories.

13. Palliflex400; maximum storage flexibility
for soft fruit.
• For long-term storage, fruit requires specific
temperatures and a specific O2 and CO2 value. This
demands a full automatic climate control system,
such as Palliflex400. up to 400 pallets can be stored
for a short or long-term period under various
Controlled Atmosphere (CA) conditions.
Storage per pallet;
• set storage conditions per pallet
• no migration of mould spores and aromatics
• no loss of CO2 when (dis)connecting units
• The system is perfect for the storage of high
valuable soft fruits and some varieties of
vegetables.
• Pallet storage means distribute a part of the stock
without unbalancing the storage conditions of the
other units. In this way,minimize product fallout and
maximize your margins because of flexible
anticipation on the market.

14. The system
• The Palliflex unit comprises a cover and a special plastic pallet on which the
product crates or packing cases can be placed.
• A gastight, transparent cover is pulled over the product. The sizes of the cover
are 1.0 m (L) x 1.2 m (W) and up to 2-5 meters in height, depending on the
product/package,maximum of 4.5 m high, is then placed on top of this.
• Up to a ton of product can then be stored within. Several times a day, the
system measures the gas conditions in the cover and corrects them
Flexible & modular
• Palliflex400 is a modular system, with a minimum of 10 and a maximum of
400 units. The system can easily be extended.

15. • Fruit varieties that are sensitive to
ethylene (under CA conditions), such as
kiwis, require an ethylene converter.
• The ethylene converter from removes
ethylene from the cool cells using
catalytic combustion; ethylene can thus
be maintained at any required level,
both in terms of a ppm range.
• Due to huge heat exchanger, the
purified air is only slightly heated.
• The ethylene converter uses oxygen to
convert ethylene into CO2 and water,
both inert substances.
Ethylene decomposers

16. Ethylene converter for;
• Maximum cooling of air, via top quality heat exchanger
(Porcelain honeycomb);
• High catalytic value via high platinum aluminium
granules (0.6 g kg-1);
• Low optimum combustion temperature of 250°C;
• A temperature difference between ingoing and
outgoing air of <5°c.
Advantages of our Porcelain Honeycomb heat-exchanger
compared to ordinary ceramic balls or grains (split):
• Improved thermal efficiency;
• Reduced pressure loss over thermal bed
• Quicker heat exchange;
• Reduced weight.

17. Humidification
Water management
• Most fruit varieties are stored under high relative humidity, above
95%. Moisture loss can limit the storage quality of fruit in a cool
cell.
• An important aspect of moisture-loss for pears, for example, is
the occurrence of ‘saggy necks’, when the skin of the pear near
the stalk begins to wrinkle. In order to avoid saggy necks, pears
must not lose over 2.5% moisture.
Measuring moisture loss (RH meters)
• Fruit that is stored in a CA-/ULO cell loses moisture. This moisture
loss reduces if the RH levels (relative humidity) are kept above 90-
95%.
• During cooling in a cell, water is taken out of the air and, as a
result, the RH level falls. The water removed then freezes on the
coolers (humidifiers) and is drained away when defrosting.
• The water meters presents that automatically limit this moisture
loss.

18. Humidification units
• There are various humidification systems that
may or may not be connected to RH meters
and/or the CA/ULO operating system;
Ultrasound humidification
• Ultrasound humidification is an excellent
solution for temperatures around and just
under zero.
• This method uses high-frequency sound
waves to move small vibration plates which
then spray out small droplets. These droplets
have a diameter of 0.5-1.0 µm and are so
small that they do not fall and freeze but
immediately evaporate in the cell air.
Pre-purification installations; Reverse Osmosis
• If water quality before humidification is
insufficiently high, a pre-purification
installation may be required. The objective of
‘Reverse Osmosis’ is to cleanse the water and
descale it so that the vibration plates are not
affected by limescale.

19. Gas-tight doors
• The doors of ULO and CA cool cells are a crucial element of
storage under low oxygen concentrations; a small leak means
that percentages of less than 3% oxygen will not be achieved.
• The gas-tight doors guarantee oxygen values of less than 0.5%
as a result of using a special rubber, inflatable profile.
• The gas-tight doors can be supplied in a horizontal or vertical
format.

20. Cold store accessories
Flexible air buffers (‘lungs’)
• Pressure fluctuations in cool cell as a result of cooling
or weather conditions can cause leaks and lead to the
addition of O2.
• A flexible air buffer is therefore vital.
• Pressure changes as a result of refrigeration or weather
conditions, for example, are balanced out by using a
flexible air buffer (‘lung’).
• The buffer is made of a durable, flexible and multi-layer
PU film. Each storage area is fitted with its own buffer.
Air buffers are sized on the basis of the volume of a
storage cell and are available in volumes of 2 - 12 m3.

21. Over and under pressure valves
• In extreme circumstances, an air buffer is
insufficient for smoothing out pressure
differences.
• In this case, an over/under pressure valve will
take up the pressure difference in storage area in
order to prevent damage from occurring.
• Every cool cell used for CA/ULO storage needs at
least one under and one over pressure valve.
Numerous valves will be used for larger cells.
Cell valves
• Scrubbers are connected to the cool cells via PVC
pipes.
• Pipes with a diameter ranging from 50 to 160
mm and corresponding cell valves are used,
depending on the type of machine.
• These cell valves are pneumatic and are,
therefore, very reliable and durable.

22. Biochemical Changes
Changes occurs in
• Flavour
• Off-flavour
• Volatile Compound
• Acidity
• Nutrition
• Acorbic acid
• Lycopene
• Phenolics

23. Flavour
• CAstored apples were shown to retain a good flavour longer than those
stored in air (Reichel,1974),
• In most fruits and vegetables CA storage generally maintains better
flavour than storage in air (Zhao and Murata, 1988;
Wang, 1990).
• However, the stage of ripeness of fruit when storage begins has the
major effect on its flavour, sweetness, acidity and texture.
• It is therefore often difficult to specify exactly what effect CA storage
has, since the effect on flavour may well be confounded with the effect
of maturity and ripening.
• An example of this was that the storage of tomatoes in low
concentrations of O2 had less effect on fruits that were subsequently
ripened than the stage of maturity at which they were harvested (Kader
et al., 1978).

24. Off-flavours
• Some of the effects on flavour of fruits and vegetables during
storage are the result of
fermentation.
• Off-flavour development is associated with increased production
of ethanol and acetaldehyde.
• For example, Mateos et al. (1993) reported that off-flavour
developed in intact lettuce heads exposed to 20% CO2, which was
associated with increased concentrations of ethanol and
acetaldehyde.

25. Volatile Compounds
• CA storage has also been shown to affect volatile compounds,
which are produced by fruits and give them their characteristic
flavour and aroma.
• Willaert et al. (1983) isolated 24 aroma compounds from Golden
Delicious apples and showed that the relative amounts of 18 of
these components declined considerably during CA storage.
• Hatfield (1975) showed that Cox’s Orange Pippin apples, after
storage in 2% O2 at 3 °C for 3.5 months and subsequent ripening
at 20 °C, produced smaller amounts of volatile esters than they
did when ripened directly after harvest or after storage in air. This
was correlated with a marked loss of flavour.
• They showed that the inhibition of volatile production could be
relieved considerably if the apples were first kept in air at 5–15 °C
after storage and before being transferred to 20 °C.

26. Acidity
• The acid levels in fruits and vegetables can obviously affect
their flavour and acceptability.
• Knee and Sharples (1979) reported that acidity could fall by as
much as 50% during storage of apples and that there was a
good correlation between fruit acidity and sensory evaluation.
Nutrition
CA storage has been shown to have both positive and negative
effects in fruits and vegetables on the synthesis and retention of
chemicals required for human nutrition other than proteins and
carbohydrates, sometimes called phytochemicals.

27. Ascorbic acid
• CA storage has been shown to hasten the loss
of ascorbic acid compared with storage in air.
• The ascorbic acid content of the tomato cultivars
Punjab Chuhara and Punjab Kesri decreased as the CO2
concentration in the storage atmosphere increased,
and increased as the storage period was lengthened
(Singh et al., 1993).
• Vidigal et al. (1979), in studies of tomatoes, found that
the ascorbic acid levels increased during CA storage at
10 °C.

29. Lycopene
Jeffery et al. (1984) showed that lycopene synthesis in
tomatoes was suppressed during storage in 6% CO2 + 6% O2.
Phenolics
• Rogiers and Knowles (2000) stored four cultivars of
Amelanchier alnifolia at 0.5 °C for 56 days in various CAs and
found that 5% CO2 + 21% O2or 5% CO2 + 10% O2 were most
effective at minimizing losses in fruit anthocyanins.
• In blueberries, CA storage had little or no effect on phenolic
content (Schotsmans et al., 2007).
• However, Zheng at al. (2003) found that total phenolics
increased in blueberries during storage at 5 °C in 60–100% O2
for 35 days to a greater extent than those stored in air or 40%
O2