Controlled atmosphere storage involves regulating oxygen, carbon dioxide, nitrogen, temperature and humidity levels in a storage room. Gases are constantly monitored and adjusted to maintain optimal levels. Scrubbers are used to absorb excess gases from the atmosphere. Modified atmosphere packaging replaces air in packaging with gases like oxygen, nitrogen or carbon dioxide to modify the atmosphere and extend shelf life of foods. Active modification involves flushing packages with gas mixtures while passive modification relies on product respiration through permeable packaging films.

1. CHAPTER ONE
INTRODUCTION
 Controlled environment: controlled
environment/atmosphere is an agricultural storage
method in which the concentrations of oxygen, carbon
dioxide and nitrogen, as well as the temperature and
humidity of a storage room are regulated.
 Both dry commodities and fresh fruit and vegetables can
be stored in controlled atmospheres.
 In controlled environment, the atmosphere is created
artificially and the gas composition is continuously
monitored and adjusted to maintain the optimum gas
concentration.
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2. INTRODUCTION
 A controlled atmosphere storage: is an agricultural storage
method in which atmosphere in which oxygen, carbon dioxide
and nitrogen concentrations as well as temperature and
humidity are regulated.
 Controlled atmosphere storage refers to the constant
monitoring and adjustment of the CO2 and O2 levels within gas
tight stores or containers.
 The gas mixture will constantly change due to metabolic
activity of the respiring fruits and vegetables in the store and
leakage of gases through doors and walls.
 The gases are therefore measured periodically and adjusted
to the predetermined level by the introduction of fresh air or
nitrogen or passing the store atmosphere through a chemical
to remove CO2.
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3.  The gas mixture will constantly change due to
metabolic activity of the respiring fruits and
vegetables in the store and leakage of gases
through doors and walls.
 The gases are therefore measured periodically and
adjusted to the predetermined level by the
introduction of fresh air or nitrogen or passing the
store atmosphere through a chemical to remove
CO2.
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4. INTRODUCTION
Importance of controlled atmosphere
The advantages of storage under controlled atmosphere are :
 better quality after storage
 longer storage period
 longer shelf-life period after storage
 higher nutritional value after storage(vitamin C)
 more environmental friendly storage(no postharvest
chemical treatments against scald are
 needed).
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5.  Controlled Atmosphere system consists the
following:
1.Nitrogen Generator with
2. Gas Analyzer & Controller with following:
 Ethylene Indicator & Controller
 CO2 Indicator & Controller
 O2 Indicator & Controller
 Humidity & Temperature Indi
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6. 3. CO2 Scrubber: consisting of CO2 Absorber, blower and
valves.
4. Ethylene Scrubber: consisting of Absorber, blower and
valves.
5. O2 Scrubber: consisting
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7. Atmosphere conditioning
 The reduction of O2 level inside the storage rooms can
be biologically achieved by means of fruit respiration,
or by O2 burning, or by replacing air by feeding
nitrogen.
 The reduction in O2 level in the atmosphere is
obtained by using nitrogen generators (by now, a
widely used system), or by feeding liquid N2.
 Nitrogen generator selectively separate air to produce
an enriched nitrogen system.
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8.  The storability of fruits and vegetables is strictly
related to their respiration rate, which is an
expression of metabolic activity. Aerobic respiration
requires O2, and results in CO2 and heat release.
 More than 95% of the energy released is lost as
heat. The temperature decrease, in particular if
helped by modification of the atmosphere leads to a
reduction in respiration rate, and therefore to an
increase in storage life in
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9. Requirements for Ideal CAS
i. CA storage room:
 A gas tight room is an obvious prerequisite for
achieving a good controlled atmosphere storage
system. Thus it is necessary to make room walls
gas -tight.
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10. Temperature Control
 The main way of preserving fruits and vegetables in storage
or during long distance transport is by refrigeration, and
controlled atmospheres are considered a supplement to
increase or enhance the effect of refrigeration.
 Controlled atmosphere storage is only successful when
applied at low temperatures. Standard refrigeration units are
therefore integral components of controlled atmosphere
stores.
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11.  Temperature control is achieved by having pipes
containing a refrigerant inside the store. Ammonia
or chlorofluorocarbons are common refrigerants.
These pipes pass out of the store; the liquid is
cooled and passed over the cooled pipes.
 Temperature control is achieved by having pipes
containing a refrigerant inside the store.
 Ammonia or chlorofluorocarbons are common
refrigerants. These pipes pass out of the store; the
liquid is cooled and passed over the cooled pipes.
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12. Humidity Control
 Humidity is the concentration of water vapor
present in the air.
 Most fruits and vegetables, which are kept in CA
storage, require a high relative humidity. Generally
the closer to saturation the better, so long as
moisture does not condense on the crop.
 The amount of heat absorbed by the cooling coils of
the refrigeration unit is related to the temperature of
the refrigerant they contain and the surface area of
the coils. 12

13.  If the refrigerant temperature is low compared to
the store air temperature then water will condense
on the evaporator.
 This removal of moisture from the store air reduces
its relative humidity, which results in the stored crop
losing moisture by evapo-transpiration.
 In order to reduce crop desiccation/dryness the
refrigerant temperature should be kept close to the
store air temperature.
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14. ii. Gas Control
 The atmosphere in a modern CA store is constantly
analyzed for CO2 and O2 levels using an Infrared
gas analyzer to measure the gas content in the
store constantly.
 There are also ethylene analyzers that continuously
measure ethylene concentration in the store.
 In storage rooms where low ethylene is essential,
checks can be made that the ventilation and
ethylene removal systems are operating correctly.
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15. Scrubbers
 The composition of the gas mixture inside the storage
rooms undergoes continuous change as a function of
the metabolic activity of the stored product and
scrubbers are necessary to absorb excess CO2.
 Scrubbers are generally classified according to the
absorbent material: CA(OH)2, NaOH, H2 O, zeolites,
activated charcoals.
 They are also classified according to them ode of
absorption (i.e. chemical or physical), or to the mode of
air passage through the absorbing agent.
 Scrubbers using activated charcoal are currently the
most popular. Gas removal with this type of equipment
is based on the fixing of CO2 in a particular way, and
releasing it again on contact with atmospheric air, even
at room temperature
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16. Scrubbers: are
used in controlled
atmosphere storage to
absorb the extra
amount gases present
inside the packaging
material.
Scrubbers
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17. DETRIMENTAL EFFECTS OF CA
(ABOVE OR BELOW OPTIMUM COMPOSITION
FOR THE COMMODITY):
• May cause irregular ripening of fruits (banana, mango,
pear, and tomato, at O2 below 2%, CO2 above 5% for >
1 month).
• May cause certain physiological disorders.
• May enhance anaerobic respiration and development
of off-flavors.
• May cause susceptibility to decay.
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18. Modified Atmosphere Packaging (MAP)
 MAP is the replacement of air (N2 content 78%, O2
content 21%, CO 2 content 0.035%,
 together with water vapor and traces of inert gases)
in a pack with a single gas or mixture of gases; the
proportion of each component is fixed when the
mixture is introduced.
 Sometimes, certain additives are incorporated into
the polymeric packaging film or within packaging
containers to modify the headspace atmosphere
and to extend shelf-life. This is referred to as Active
Packaging.
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19.  Modified atmosphere can be created also passively.
In passive modification, the respiring product is
placed in a polymeric package and sealed
hermetically. Only the respiration of the product and
the gas permeability of the film influence the
change in gaseous composition of the environment
surrounding the product. If the product’s respiration
characteristics are properly matched to the films
permeability values, then a beneficial modified
atmosphere can be passively created within a
package.
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20. Gases used in MAP
In MAP, the pack is flushed with a gas or a
combination of gases. The common gases used Are:
 oxygen,
 nitrogen and
 carbon dioxide.
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21.  Traces of carbon monoxide, nitrous oxide, ozone, argon, ethanol,
vapor and sculpture dioxide are also used.
 Minimum oxygen levels are used to pack food under MA
because oxygen reacts with the foodstuff resulting in the
oxidative breakdown of food into their constitutive parts. Oxygen
also combines easily with fats and oils causing rancidity.
 Nitrogen is an inert gas. It has no anti-microbial activity and acts
as a cushion, thereby preventing pack collapse. Since it
displaces oxygen from the pack, oxidative rancidity is delayed.
 Carbon dioxide is responsible for the bacteriostatic and fungi
static effect in MA packaged food.
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22. Modified atmosphere packaging (MAP)
➢Modified Atmosphere Packaging (MAP) involves the
modification of the head space gas in a package in
order to prolong the shelf life of the product it
contains.
➢The greatest use of MAP is for fresh-cut products (to
maintain 2-5% O2 and 8-12% CO2).
➢It is possible to improve gas control in MAP by
adding absorbers of ethylene, carbon dioxide and
oxygen.
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23. ➢ O₂ absorber:- Iron powder is used commercially as
the active ingredient. Ex. FeO, Fe₂O₃, Fe₃O₄
➢ CO₂ absorber:- Lime(freshly hydrated high
calcium lime (Ca(OH)₂),activated charcoal,
magnesium oxide)
➢ Ethylene absorber:- Potassium permanganate,
builder clay powder, hydrocarbons, silicones
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24. TYPES OF MODIFIED ATMOSPHERE
➢Active modification
The atmosphere is modified by pulling a slight
vacuum and replacing the packaging atmophere within
the desired gas mixture.
➢Passive modification
Modification is achieved by respiration of
commodity within the package and depends on the
characteristics of the commodity and the packaging
film. 24

25. ➢ Passive modification
• Product packaged with selected film
• Desired atmosphere develops naturally over time
• Takes longer to achieve desired atmosphere in
package
➢ Active modification
• Displace or remove gases in package
• Replace with mix of desired gases an seal
• Better shelf life is achieved with Active
Modification
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