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Fruit & Vegetable Storage
• I. INTRODUCTION
• Proper marketing of perishable commodities such as
fruits and vegetables often requires some storage to
balance day-to-day fluctuations between harvest and
sale or for long-term storage to extend marketing
beyond the end of harvest season.
• Storage of fresh fruits and vegetables prolongs their
usefulness and in some cases, improves their
quality; it also controls a market glut.
• The principal goal of storage is to control the rate of
transpiration, respiration, disease, and insect
infestation and to preserve the commodity in its
most usable form for the consumer.
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• Storage life can be prolonged by
 harvesting at proper maturity (Figure 1),
 control of postharvest diseases,
 regulation of atmosphere, chemical treatments,
 irradiation, refrigeration,
 controlled and modified atmospheres, and
 by several other treatments.
• The main goals of storage are to
• (I) slow the biological activity of fruits and
vegetables without chilling injury;
• (2) slow the growth of microorganisms,
• (3) reduce transpirational losses.
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• A. PRINCIPLES OF STORAGE
• Since all fruits and vegetables are living tissues, the
tendency after harvest is to continue respiration.
• Thus, proper and adequate storage conditions must be
maintained, otherwise
the following undesirable processes may occur in
certain vegetables:
 1.Sprouting—potatoes, onions, ginger, garlic
2. Elongation—asparagus, carrots, beets,
 3. Rooting—due to increased humidity which may
result in rapid decay, shrivelling, and exhaustion of
food reserves
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 4. Greening—exposure of potatoes to light during
storage may produce green tissue and synthesis of
toxic glycoalkaloids such as solanine and chaconine
 5. Toughening—green beans, sweet corn may
toughen due to prolonged storage at relatively high
temperatures
• The Following factors need to be considered for
success of produce storage.
1. Temperature
Temperature in a storage room should normally be
maintained at the desired temperature for
commodities being stored.
Delay in cold storage reduces marketability of
fruits and vegetables)
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Temperatures below the optimum range for a
given fruit or a vegetable will cause freezing or
chilling injuries, temperatures above, depending
upon produce, will reduce storage life.
• A wide temperature fluctuation can result in rapid
weight and water loss depending upon maturity of
produce.
• The USDA Agricultural Handbook number 66 lists
recommended storage temperatures and relative
humidities for various fruits and vegetables.
• The refrigeration temperature within the
recommended range is a result of several
important design factors.
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• Temperature variation within the room is
minimized by incorporating adequate amounts
of insulating material in the walls and by
maintaining adequate levels of air circulation in
the room.
• When the room is filled, the containers should
be stacked to allow an air passage along at least
one side of each container.
• Thermostats are placed at a height of five feet
from the floor for ease in checking locations.
• A calibrated thermometer should he used to
periodically check the thermostat.
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• 2. RELATIVE HUMIDITY
• For most perishable fresh fruits and vegetables, the
relative humidity should be maintained between 90
to 95%.
• The relative humidity below this range will result
in a moisture loss from the produce (Table 1).
• Thus the produce will be shrivelled and limp.
Relative humidity if higher than 90% may cause
excessive growth of microorganisms.
• Refrigeration equipment must be especially
designed to maintain a higher relative humidity.
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• The environmental factors of temperature, relative
humidity and vapor pressure deficit are important in
the storage life of fruits and vegetables.
• A 5 to 10% loss in weight of produce results in
shrivelling, which makes the produce look stale and
unattractive to sell.
• By using high relative humidity during storage, care
must be taken to prevent the growth of surface
microorganisms
• 3. ATMOSPHERIC COMPOSITION
• The atmospheric composition in a storage room is
controlled by addition of gases allowing the
commodity to produce or consume gases or by
physically or chemically removing undesirable gases
from the storage room.
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• Gases such as carbon monoxide (CO), carbon dioxide
(CO2), ethylene (C2H4), and nitrogen (N2) can be
added to a facility from a bottled supply (or dry ice in
the case of C02) or produced by on-site generators.
• As the perishable fruits and vegetables undergo
respiration, they consume 02 and release CO2.
• This effect can be successfully used to control the
desired concentration of these gases in storage.
• High concentration of undesirable gases are removed
by scrubbing devices.
• For example, CO2 can be absorbed in water or lime;
• C2H4 and other volatiles can be removed by
potassium permanganate, catalytic oxidation or UV
light; and
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• O2 can be removed by using it in a combustion
process or by a molecular sieve.
• In certain cases external concentrations of gases are
desirable and the accumulated gases can be adjusted
by ventilation.
• 4. LIGHT AND OTHER FACTORS
• Exposure of potato tubers to light in grocery stores
can synthesize glycoalkaloids (solanine and
chalkonine) which are toxic to humans.
• Likewise, other factors such as herbicides,
fungicides, pesticides and growth regulators may
affect the produce and may have harmful affects on
humans.
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B. STORAGE OPERATIONS
• The increase of fruit and vegetable
production, owing to large acreage and
high-yielding cultivars requires sufficient
storage space.
• Accordingly, storage operations have
evolved into skilled methods of efficiency
with a wide range of variations depending
upon the existing facilities, including
nature and the variety and quantity of
produce to be stored.
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• Storage operations may be either temporary,
short-term or long-term.
• Temporary storage operations are needed for
highly perishable produce which requires
immediate marketing. It may be installed with or
without refrigeration.
• Temporary storage is extremely important for
roadside stands, gardens, markets, railway
stations, shipping yards and retail stores.
• The mid-term storage operation is aimed at
checking the market glut without product
deterioration.
• This may extend from I to 6 weeks depending
upon the need, kind, and maturity of the produce.
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• Mango, banana, papaya, cabbage, eggplant,
tomatoes, cauliflower and french bean are
transferred to short-term storage rooms, when
their quality is still good, and held there until a
reasonable market price is attained.
• Fruits and vegetables like apples, oranges, pears,
squash, potatoes, sweet potatoes, carrots, onions,
garlic, and pumpkins require long- term storage.
• Its operations are mainly influenced by economic
factors. The produce is stored during their
periods of production, and sold continuously
during the rest of the year when producers and
dealers can obtain reasonably high prices.
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• Storage operations may be classified as either natural
or artificial.
• The natural storage operation keeps the produce in
situ without any treatment, whereas artificial storage
may be further classified into four types:
 (I) mechanical or structural, (2) controlled
atmosphere. (3) chemical, and (4) radiation.
• In case of natural storage, the main purpose is to let
the fruits or vegetables mature and ripen on plants as
long as possible;
• on the other hand, artificial storage operations
attempt to provide conditions to prolong the produce
quality.
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1. Natural Storage
Vegetables such as potato, sweet potato, and
garlic are kept underground for several months.
They are harvested prior to the rainy season for a
better market price.
This harvesting does not involve extra
expenditure and building for storage.
2. Artificial Storage
Pits or trenches are dug underground for storing
beets, potatoes, onions, carrots, turnips, cabbages,
and sweet potatoes where they are covered with
straw and soil until there is a market demand
(Figures 2 and 3).
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• 3. Ventilated Storage
• Cellars are underground rooms with slanting roofs
covered with sods and soils.
• The structure may be built into the hillside and
covered with additional soil.
• Cellars are provided with heaters and dry
atmospheres during winter months.
• Potatoes, turnips, carrots and beets are stored with
high relative humidity at (1 .7—4.4°C).
• Where snow is prevalent, a good cellar will
provide satisfactory storage for hard vegetables
and fruits. Above-ground warehouses may be used
to store produce.
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• In cold weather the produce is covered with
blankets to protect from cold temperatures.
• Ventilation is essential for good storage.
• Potatoes, onions, garlic bulbs, crucifer leafy
vegetables and fruits are stored successfully.
• This storage structure has several advantages over
other types:
 (I) special construction i not needed;
 (2) produce is easily handled;
 (3) grading, storing, packaging of fruits andvegetables is facilitated;
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 (4) air may be humidified; and
 (5) fans can be controlled manually or automatically
with a thermostat.
• 4. Ice Refrigeration
• An advance on the above-ground warehouses was the
use of ice as a refrigerant.
• Lower temperatures obtained enable longer storage of
meat and perishable fruits and vegetables.
• Ice can be obtained in winter from frozen Lakes and
ponds and stored in ice houses.
• The melting of 1 kg of ice absorbs 325 kilojoules.
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• However, removal of melted ice water is a
disadvantage.
• The introduction of a small ice box was a great
advance on the domestic level, and for small-scale
commercial storage of fruits and vegetables.
• II. MECHANICAL REFRIGERATION
• Refrigerated storage makes possible the marketing
of perishable fruits and vegetables beyond their
harvest season.
• In developped countries, most of the fruits and
vegetables are available year-round to consumers.
• This is due to the refrigerated storage.
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• Most storage facilities use mechanical
refrigeration to control the desired temperature.
This system utilizes the fact that a liquid
absorbs heat as it changes to gas
• A common mechanical refrigeration system
(Figure 6) uses a refrigerant such as ammonia or
freon where vapor can be easily recaptured by a
compressor.
• Heat exchange methods of heat transfer play an
important part in the refrigeration of fruits and
vegetables in maintaining the desired
temperature in a refrigerator or a refrigerated
warehouse.
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• The refrigerant (ammonia or freon) passes through an
expansion valve where its pressure drops and liquid
evaporates at temperatures low enough to be effective
in removing heat from the storage area.
• Heat needed for evaporation comes from the fruits
and vegetables to be cooled.
• Heat is transferred to the product in the storage room
and is forced past the evaporator (cooling coils).
• The evaporator is located in the storage room.
• The gas is re-pressurized by the compressor and then
passed through a condenser where it is cooled to a
liquid.
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• The condenser is located outside the storage area and
rejects heat.
• A liquid (ammonia or freon) is stored in the receiver
and is metered out as needed to produce an essential
or a desired cooling temperature
• The basic equipment and material for mechanical
refrigeration are as follows
 (I) expansion valve,
 (2) evaporator,
 (3) compressor.
 (4) condenser and
 (5) refrigerant.
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Areas to consider regarding the refrigerant are
• Cost of refrigerant—freons are more
expensive than ammonia.
• Compatibility—ammonia cannot be used
with metals that contain copper.
• Toxicity—ammonia even at low
concentration can cause injury to fruits and
vegetables.
 In summary, the basic equipment for
mechanical refrigeration consists of
compressor, condenser, expansion valve, and
evaporator.
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• The refrigerant (ammonia or freon) is
 compressed,
 cooled by passing through an air- or water-cooled
condenser, and then
 expanded through an expansion valve into
evaporator coils.
• During this evaporation and expansion phase, heat
is absorbed from fruits, vegetables, and the area to
be cooled.
• The absorbed heat is returned for eventual
elimination in the condenser.
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• All modem room-refrigeration systems provide
forced-air circulation.
• This system uses prefabricated units containing
both evaporator coils and blowers for air
circulation. They provide excellent storage
environment.
• Substantial heat must be removed quickly from the
produce in storage;
• it is apparent that greater refrigeration capacity and
air velocity must be available.
• A success of mechanical- refrigeration storage
rooms depends upon controlled temperature,
relative humidity, and air movement.
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• A. TEMPERATURE
• Temperature control depends upon a tight, wellinsulated structure and sufficient refrigeration
capacity.
• It also depends on the amount and nature of the
evaporator-coil surface, its freedom from condensed
ice, and the rate of air flowing over the coils. These
factors control the total efficiency of refrigeration.
B. RELATIVE HUMIDITY
• Relative humidity is the percentage of saturated water
vapor at a given temperature.
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• Relative humidity (%) can be determined from
psychrometric charts or the basis of wet- bulb and
dry-bulb temperatures .
• As the temperature of air increases so does its waterholding capacity.
• Accordingly, air with 90% RH at (21°C) contains
much more water than air of the same relative
humidity at (4°C).
• As the relative humidity of air decreases, so does its
vapor pressure and as vapor pressure decreases, the
capacity of the air for removing water from moist
sources increases.
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• Thus it is important to maintain a high vapor
pressure. If drying is to he avoided, a small
vapor pressure differential between stored
produce and storage air must be obtained.
• Effective ways of accomplishing this is by
 rapid equalization of produce and air
temperature,
 maintenance of high relative humidity in the
storage room air as the produce will tolerate
and
 no more air movement than is required for even
temperature distribution in the refrigerated
room.
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• An efficient system for maintenance of high relative
humidity is the modification in the construction of
the storage room.
• The jacketed storage room is built so that the cooling
air circulates around the room in a sealed envelope.
• This maintains uniform temperature and relative
humidity. This reduces moisture loss by condensation
on the cooling system. In addition, air movement in
the room reduces moisture loss from the produce.
• C. AIR MOVEMENT
• Air movement must be sufficient enough to remove
respiration heat. It is essential that all parts of the
room are subjected to a uniform flow of air.
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• This is accomplished by proper placement of
blowers or ducts and stacking of fruits and
vegetables to permit free air flow.
• The successful operation of a large refrigeration
system requires an efficient control system.
• Microcomputers are presently used to allow
precise controls for large warehouse refrigeration
systems.
• The defrosting cycle should be set to accomplish
the process automatically.
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• The capacity of a refrigeration system is based upon
adding all the heat inputs to a storage area. Heat inputs
include:
 1. Heat conducted through walls, floor, and ceiling.
 2. Field and respiration heat of fruits and vegetables.
 3. Heat from air filtration.
 4 Heat from equipment such as light, fan, forklift, and
personnel moving in and out.
• If controlled and modified atmospheres are used in
conjunction with refrigeration, the vapor barrier may
serve as a gas bather.
• Hence, special precautions must be taken to insure a
gas-tight seal. This operation should be done under the
supervision of an experienced refrigeration engineer.
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III. CONTROLLED AND MODIFIED ATMOSPHERE
STORAGES
• The principle of storage under high CO2 and low O2
appears to have been applied in ancient times.
• The earliest use of controlled-modified atmospheric
storage may be attributed to the Chinese.
• Ancient Chinese writings reported that litchi fruits
were transported from northern China to southern
China in sealed clay pots to which fresh leaves and
grass were added.
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• It may be surprised that during the 2-week journey,
respiration of the fruits, leaves, and grass generated a
high-carbon dioxide—low-oxygen atmosphere in the
pots which retarded ripening of the litchis.
• The first scientific observations of the effects of
atmosphere on fruit ripening were made in 1819-20 by
Berard, a Professor of Chemistry at Montpelier
Institute in France.
• Several further independent studies of the effects of
controlled atmospheres on fruit ripening were made in
the United States.
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• One study involved the construction of a primitive
controlled-atmosphere store in which apples were
successfully stored.
• However, it was not until the work of Kidd and West
at the Low Temperature Research Station at
Cambridge, England that a sound basis of the
controlled-atmosphere storage of produce was
established in 1927.
• During the last sixty years, the effects of controlled,
modified atmospheres—hypobaric storage— have
been extensively studied on fresh fruits arid
vegetables (Tables 2 and 3).
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• Controlled and modified atmosphere storages (MA
and CA) indicate the removal or addition of gases
resulting in an atmosphere composition for fruits
and vegetables and their products that is different
that of air (75% N2, 21% O2 and 0.03% CO2) .
• MA and CA differ in the degree of control;
• CA is more exact than MA.
• In MA gases are not controlled at specific
concentration.
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• CA: CA when combined with refrigeration, retards
respiration of fruits and vegetables,
• delay softening, yellowing spoilage and other
breakdown processes by maintaining an atmosphere
with more CO2 and less O2 than in normal air.
• CA is utilized now on commercial scale, and more
than 50% of the US apples and Palestinian oranges
are stored under CA condition.
• Tables 1 and 3 shows the different type of storage for
some fruits and vegetables.
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• Storage terms:
• many terms are used in the field of fruits and
vegetables storage.
• Some of there terms like refrigerated storage, CA
and MA storage has been covered.
• Additionally, MA includes the packaging in film
bags that requires a decrease in O2 and increase in
CO2 or N2 but without precise control.
• Gas storage is another term sometimes used to
differentiate between CA or MA and air storage.
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• However if one gas is only used, in such cases the
storage is named with that gas like CO2 storage, N2
storage…etc.
• Vacuum storage, hypobaric storage or subatmospheric pressure storage are names for one
type of storage which is a type of CA storage.
• It refers to the storage of fruits and vegetables
under control atmosphere storage in addition to
maintaining a low pressure on the produce which
will result in more extending shelf life by diffusion
of ethylene from the tissues by evacuation.
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• Metabolic effect of CA :
• many studies showed that CA may have the
following effects on the stored fruits and
vegetables:
 retard respiration,
 cause acid accumulation and acetaldehyde
formation,
 increase sugars,
 decrease alcohol soluble and protein N,
 causes pectin changes and
 inhibit chlorophyll degradation.
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• Adverse and toxic effects of CA:
• controlled atmosphere storage has great
advantages and can have some adverse effects on
fruits and vegetables.
• High levels of CO2 and low concentration of O2
(tables 4 and 5) may cause:
 Decay
 internal browning,
 breakdown and
 accumulation of some organic acids such as
succinic acid of toxic levels (0.001 M).
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• Physiological effects of high CO2 level:
• higher levels of CO2 during CA storage of fruits and
vegetables may have some effects on
 ripening,
 enzyme activity,
 production of volatile,
 metabolism of organic acids,
 breakdown of pectic substances,
 chlorophyll synthesis and fruit degreening and
 types and proportions of present sugars.
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• Higher levels of CO2 also
 alters the climacteric pattern in fruits and vegetables,
 produces off-flavors,
 increase the PH and reduce ascorbic acid content,
 retards fungal growth,
 affects C2H4 production or function and
 may cause (high level of O2) some physiological
disorders like brown heart and scald.
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• Humidity and C2H4 control during CA
storage:
• it is also recommended to control both C2H4
and humidity during CA storage of fruits and
vegetables in addition to controlling of O2 and
CO2 and temperature.
• Accumulation of C2H4 will cause degreening
and ripening of fruits and vegetables, so
absorption of C2H4 by KMNO4 is advised.
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• Also in commercial CA storage humidity
reaches to saturation in storage of some fruits
and vegetables and this may encourage the
growth of fungi.
• As a result it is advised to apply a suitable
fungicide to retard the fungi growth.
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• Behavior of fruits and vegetables after CA
storage:
• after the removal of fruits and vegetables from
CA storage, they may have some change like
 increased respiration rate,
 appearance of tissue browning and decease in
firmness.
• However, many investigation noticed that the
organoleptic properties of fruits and vegetables
after CA storage is more better than those after
refrigerated storage provided that the CA
conditions were properly selected.
•
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• CA storage duration (long or short):
• CA storage for a long time may cause injuries to
fruits and vegetables inspite of the properly selected
conditions.
• However, storage life of fruits and vegetables in CA
storage may be 50% longer than in air storage.
• Results regarding the CA storage for short time are of
vital importance specially to be applied in
transportation.
• The effect of different levels of O2 or/and CO2
during CA storage for short time for some fruits and
vegetables have been studied but further research is
needed.
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• Including of CO in CA storage was found to be
beneficial especially with regard to control fungal
decay and to inhibit discoloration (5-10%
concentration).
• Advantages and disadvantages of CA and MA
storage:
• the advantages or benefits include
 retardation of senescence,
 reduction of produce sensitivity to C2H4,
 controlling some of the physiological disorders like
chilling injury and also
 controlling postharvest disease and decaying.
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• The limitations or disadvantages include
 increasing some of the postharvest disorder like sprouting in
potatoes, brown heart in apples;
 irregular ripening of bananas and tomatoes,
 development of off-flavor and
 in some cases increasing the susceptibility to decay.
• Something of interest in CA storage that there is no single
best combination of CO2 and O2 for mixed storage of fruits
and vegetables.
• Instead each species and may be each cultivar varies in its
CA requirements.
• Tables 6 and 7 show the CA requirements from O2 and CO2
for some of the important fruits and vegetables..
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• Storage in polymeric films:
• great progress has been achieved in the field of
developing a produce package for CA storage.
• These packages are perforated and semipermeable
and aim at
 reducing moisture loss,
 protect the produce from mechanical damage and
 improve its appearance.
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• In the produce package, respiration occurs by the
produce and permeation by the package.
• In other words the produce takes up O2 and gives
CO2, H2H4 and volatiles while the package
according to its permeability permit the escape of
these gases.
• However, the package system should be in such a
way to achieve steady state condition where
equilibrium concentration of O2 and CO2 is reached.
• Many factors interfere or affect this steady conditions
such as
 the type of produce,
 its weight,
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 variety,
 respiration rate,
 stage of maturity,
 temperature,
 O2 and CO2 level needed,
 C2H4 concentration,
 light,
 film thickness,
 film permeability and
 others.
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• However, all these factors should be considered in
selecting the proper package for any given fresh
produce.
• Due to the complexity of controlling such large
variable, the computer has been utilized for such
purposes and a good results have been achieved.
• It is also of value to note that packaged apples have
a longer shelf life than control apples with about
two months.
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• Vacuum storage:
• it may be classified to two types:
 the first include the gas-flush packaging where the
air in the package is replaced by another gas such
as CO2 or N2 and it is used for packaging of
salads, fruits juices and minimally processed fruits
and vegetables,
 the second type is that where all air is removed and
a vacuum is created.
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• High density polyethylene films are used for
this purpose and this packaging technique is
utilized for minimally processed fruits and
vegetables.
• Something to be considered here is to leave
some O2 in the package for normal
respiration and the packaged produce
should be stored at 5C or under refrigeration
to avoid deterioration.
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• Sub atmospheric (low pressure or
hypobaric) storage:
• the storage life of many fruits and vegetables
can be extended by reduced pressure under
refrigeration due to low respiration rate and
evacuation of C2H4.
• However, the hypobaric storage is a form of
CA storage.
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• Regarding the principles of hypobaric storage; the
produce is placed at a given temperature in a sealed
container and a constant sub atmospheric pressure is
maintained by continuous evacuation;
• the produce is ventilated by air saturated with water
vapor and containing suitable fungicides in some
cases.
• It is of interest to note that at lower pressure storage
such as 278 mm Hg or less, microorganism growth
retardation is achieved.
•
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• Radurization:
• it is meant by this term the utilization of ionizing
radiation materials such as cobalt, cesium and uranium
is utilized.
• Only beta and gamma radiation kinds are utilized in
food preservation;
• beta radiation is used for food pasteurization and in the
case of gamma radiation, it is utilized for food
sterilization.
• Retardation of sprouting and rooting by radiation are
practiced commercially.
• In case of pasteurization a dose of 1 megarad is utilized,
while for sterilization a dose higher than 1 Mrad is
used.
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Future of Modified Atmosphere Research
•
•
•
•
•
•
A.A. Kader
Department of Plant Sciences
University of California
One Shields Avenue
Davis, CA 95616, USA
Keywords: controlled atmospheres, flavor quality,
fruits, vegetables
• Proc. IXth Intl. Contr. Atmos. Res. Conf.
• Ed.: R.M. Beaudry
• Acta Hort. 857, ISHS 2010
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Abstract
• It is not possible to discuss the future of modified
atmosphere (MA) research without considering the
broader aspects of research aimed at maintaining
quality of fresh horticultural perishables between
harvest and consumption.
• Providing better flavored fruits and vegetables is
likely to increase their consumption, which would be
good for the producers and marketers (making more
money or at least staying in business) as well as for
the consumers (increased consumption of healthy
foods).
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• To achieve this goal, we and all those involved
in producing and marketing fruits and
vegetables need to:
(1) replace poor flavor cultivars with good
flavor cultivars from among those that already
exist and/or by selecting new cultivars with
superior flavor and good texture;
(2) identify optimal cultural practices that
maximize flavor quality, such as optimizing
crop load and avoiding excess nitrogen and
water.
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 (3)encourage producers to harvest fruits at partiallyripe to fully-ripe stages and
vegetables at their optimal maturity stages by
developing handling methods that
protect these commodities from physical damage;
 (4) identify optimal postharvest handling conditions
(time, temperature, relative humidity, atmospheric
composition) that maintain flavor quality of fruits and
vegetables and their value-added products.
• Postharvest-life should be determined on the basis of
flavor rather than appearance.
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• The end of flavor-life results from losses in sugars,
acids and aroma volatiles (especially esters) and/or
development of off-flavors (due to fermentative
metabolism or odor transfer from fungi or other
sources);
 (5) develop ready-to-eat, value-added products with
good flavor; and
 (6) optimize maturity/ ripeness stage at the time of
processing and select processing methods to retain
good flavor of the processed products.
• Future modified atmosphere research can be part of
research on strategies number 4, 5 and 6 listed above.
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• Continued improvements in polymeric films and
other packaging materials will facilitate expanded
use of MA packaging to extend
postharvest-life of fresh-cut fruits and vegetables
and permit their distribution via vending machines.
• More cost-effective methods for establishing and
maintaining MAs will facilitate their use during
storage at shipping points, transportation and storage
at destination points.
• Maintaining the MA chain is the second most
important factor after the cold chain in keeping
quality and safety of fresh produce
between harvest and consumption.
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• Further evaluations are needed of:
• (1) the synergistic effects of MA and the ethyleneaction-inhibitor,1-methylcyclopropene, on delaying
ripening of partially-ripe climacteric fruits and
senescence of vegetables ;
• (2) MA as a component of postharvest integrated pest
management (decay and insect control);
• (3) MA in relation to food safety considerations; and
(4) the biological bases of MA effects on fresh
horticultural perishables.
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TRENDS IN MARKETING FRESH PRODUCE
• Current trends that are expected to continue in the
future include globalization of produce marketing,
consolidation or formation of alliances among
producers and marketers from various production
areas, consolidation of retail marketing organizations
and increased demand for year round supply of many
produce items with better flavor.
• Maintaining the cold chain and the modified
atmosphere chain when needed are very important to
globalization of produce marketing.
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• For some commodities (such as apples, pears and
kiwifruits), a year round supply from northern and
southern hemisphere countries eliminates price
incentives to domestic producers for “out-of-season”
produce.
• This reduces the need for CA storage beyond 6 or 7
months in either hemisphere and has the potential of
providing the consumers with better flavor-quality
fruits.
• Also, there will be opportunities for using available
CA storage facilities to store fruits from the other
hemisphere (that are transported under optimal CA
conditions) after the end of storage of locally
produced fruits.
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FLAVOR QUALITY OF FRUITS AND VEGETABLES
• It is not possible to discuss the future of modified
atmosphere (MA) research without considering the
broader aspects of research aimed at maintaining
quality of fresh horticultural perishables between
harvest and consumption.
• Flavor attributes and associated constituents include
sweetness (sugars), sourness or acidity (acids),
astringency (tannins), bitterness (isocoumarins),
aroma (odor-active volatile compounds), off-flavors
(acetaldehyde, ethanol, and/or ethyl acetate above
certain concentrations) and off-odors
(sulfurous compounds above certain concentrations).
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• Nutritional quality of fruits and vegetables is
determined by their contents of vitamins,
minerals, dietary fiber and antioxidant
phytochemicals, such as carotenoids and
flavonoids.
• It is important to determine the effects of
modified atmospheres during postharvest
handling on these constituents as indicators of
flavor and nutritional quality of intact and
fresh-cut fruits and vegetables.
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• Providing better flavored fruits and vegetables
is likely to increase their consumption, which
would be good for the producers and marketers
(making more money or at least staying in
business) as well as for the consumers
(increased consumption of healthy foods).
• To achieve this goal, we and all those involved
in producing and marketing fruits and
vegetables need to do the following:
• 1. Replace poor flavor cultivars with good
flavor cultivars from among those that already
exist and/or by selecting new cultivars with
superior flavor and good textural quality.
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• 2. Identify optimal cultural practices that
maximize flavor quality, such as optimizing
crop load and avoiding excess nitrogen and
water, which along with low calcium shorten
the postharvest-life of the fruits and vegetables
due to increased susceptibility to physical
damage, physiological disorders and decay.
• 3. Encourage producers to harvest fruits at
partially-ripe to fully-ripe stages and harvest
vegetables at their optimal maturity stages by
developing handling methods that
protect these commodities from physical
damage.
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• 4. Identify optimal postharvest handling
conditions (time, temperature, relative
humidity, atmospheric composition) that
maintain flavor quality of fruits and vegetables
and their value-added products.
• Postharvest-life should be determined on the
basis of flavor rather than appearance.
• Most of the published estimates of postharvestlife under modified or controlled atmospheres
are based on appearance (visual) quality, and
in some cases, textural quality.
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• These estimates should be revised to reflect the
end of flavor-life when the product looks good
but does not taste good.
• The end of flavor-life results from losses in
sugars, acids and aroma volatiles (especially
esters) and/or development of off-flavors (due
to fermentative metabolism or odor transfer
from fungi or other sources).
• The possible role of modified atmospheres in
delaying these undesirable changes should be
investigated.
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• 5. Develop ready-to-eat, value-added products
with good flavor. A very important research
area is to find the optimal atmospheres for
delaying browning and softening of fresh-cut
products during distribution within the optimal
ranges of temperature and relative humidity.
• 6. Optimize maturity/ ripeness stage at the time
of processing and select processing methods to
retain good flavor of the processed products.
• Future modified atmosphere research can be
part of research on strategies number4, 5 and 6
listed above.
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MAINTAINING THE MA CHAIN
• Continued improvements in polymeric films and
other packaging materials will facilitate expanded use
of MA packaging to extend postharvest-life of freshcut fruits and vegetables and permit their distribution
via vending machines and quick-service restaurants.
• MAP is an effective way to maintain the desired
atmospheric composition between shipping point and
the consumer’s home.
• When evaluating polymeric films, it is important to
place the control product in perforated plastic bags to
separate the effect of the film on reducing water loss
from its effect as a barrier to carbon dioxide and
oxygen diffusion.
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• Instead of developing more models for MAP,
researchers are encouraged to
• build upon existing models and improve their
accuracy.
• Although much research has been done on the use of
surface coatings to modify the atmosphere within
many commodities, this technology has not been used
to any extent because of the variability in
composition among batches of the coating material.
• When combined with the natural variation in the gas
diffusion characteristics among individual commodity
units, a portion of each lot is lost due to off-flavors
caused by fermentative metabolites.
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• Further research is needed to overcome these
constraints to use of surface coatings for modification
of internal atmospheres of fruits and vegetables.
• More cost-effective methods for establishing and
maintaining MAs will facilitate their use during
storage at shipping points, transportation and storage
at destination points.
• Maintaining the MA chain is the second most
important factor after the cold chain in keeping
quality and safety of fresh produce between harvest
and consumption.
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COMBINED EFFECTS OF MA AND 1-MCP
• Further evaluations are needed of the
synergistic effects of MA and the
ethyleneaction-inhibitor,
1-methylcyclopropene, on delaying ripening of
partially-ripe climacteric fruits and senescence
of vegetables and deterioration (browning and
softening) of fres-hcut products.
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MA FOR DECAY AND INSECT CONTROL
• More research is needed to evaluate the
efficacy of MA as a component of postharvest
integrated pest management (decay and insect
control) in fresh horticultural perishables.
• The fungistatic and insecticidal effects of low
oxygen, elevated carbon dioxide and
superatmospheric oxygen MA alone or in
combination with other treatments merit
further investigation.
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MA AND FOOD SAFETY CONSIDERATIONS
• More research is needed to quantify the effects
of MA on growth of pathogenic bacteria on
fresh produce and on production of
mycotoxins by fungi.
• Also, we need to understand how do high
oxygen concentrations alone or in combination
with elevated carbon dioxide concentrations
influence growth of decay-causing bacteria
and fungi and of human pathogens?
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BIOLOGICAL BASES OF MA EFFECTS
• Studies of the biological bases of MA effects on fresh
horticultural perishables should be expanded to include
superatmospheric oxygen concentrations and their
interactions with elevated carbon dioxide levels.
• RETURN ON INVESTMENT OF MA
• Future expansion in the commercial use of MAP, MA during
transport and CA storage will depend on demonstrating a
positive return on investment (ROI).
• Thus, it is important to estimate the ROI of every application
before recommending its use.
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Selected References
• Al-Ati, T. and Hotchkiss, J.H. 2003. The role of packaging film
permselectivity in modified atmosphere packaging. J. Agric. Food Chem.
51:4133–4138.
• Amarante, C. and Banks, N.H. 2001. Postharvest physiology and quality of
coated fruits and vegetables. Hort. Rev. 26:161–238.
• Beaudry, R.M. 2000. Responses of horticultural commodities to low
oxygen: limits to the expanded use of modified atmosphere packaging.
HortTechnology 10:491–500.
• Blankenship, S.M. and Dole, J.M. 2003. 1-Methylcyclopropene: a review.
Postharvest Biol. Technol. 28:1–25.
• Brecht, J.K., Chau, K.V., Fonseca, S.C., Oliveira, F.A.R., Silva, F.M.,
Nunes, M.C.N. and Bender, R.J. 2003. Maintaining optimal atmosphere
conditions for fruits and vegetables throughout the postharvest handling
chain. Postharvest Biol. Technol.
27:87–101.
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• Burg, S.P. 2004. Postharvest physiology and hypobaric storage of fresh
produce. CABI publishing, Wallingford, UK, p.654.
• Fonseca, S.C., Oliveira, F.A.R., Lino, I.B.M., Brecht, J.K. and Chau, K.V.
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• Modelling O2 and CO2 exchange for development of perforation-mediated
modified atmosphere packaging. J. Food Eng. 43:9–16.
• Gross, K., Wang, C.Y. and Saltveit, M.E. (eds.). 2004. The commercial
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• Hagenmaier, R.D. 2005. A comparison of ethane, ethylene, and CO2 peel
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• Kader, A.A. (Ed.). 2001. CA Bibliography (1981-2000) and CA
Recommendations (2001), CD. University of California, Postharvest
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• Kader, A.A. 2003a. Physiology of CA treated produce. Acta Hort. 600:349–
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• Kader, A.A. and Ben-Yehoshua, S. 2000. Effects of superatmospheric
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• Kader, A.A. and Watkins, C.B. 2000. Modified atmosphere packagingtoward 2000 and beyond. HortTechnology 10:483–486.
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• Mitcham, E.J. 2003. Controlled atmospheres for insect and mite control in
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• Oosterhaven, J. and Peppelenbos, H.W. (Eds.). 2003. Proceeding of the
Eighth International Controlled Atmosphere Research Conference. Acta
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• Pesis, E. 2005. The role of the anaerobic metabolites, acetaldehyde and
ethanol, in fruit ripening, enhancement of fruit quality and fruit
deterioration. Postharvest Biol. Technol. 37:1–19.
• Saltveit, M.E. 2003. Is it possible to find an optimal controlled atmosphere?
Postharvest Biol. Technol. 27:3–13.
• Schotsmans, W., Verlinden, B.E., Lammertyn, J. and Nicolai, B.M. 2003.
Simultaneous measurement of oxygen and carbon dioxide diffusivity in
pear fruit tissue. Postharvest Biol. Technol. 29:155–166.
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• Soliva-Fortuny, R.C. and Martin-Belloso, O. 2003. New advances in
extending the shelflife of fresh-cut fruits: a review. Trends Food Sci.
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• Suppakul, P., Miltz, J., Sonneveld, K. and Bigger, S.W. 2003. Active
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• Veltman, R.H., Verschoor, J.A. and Ruijsch-van Dugteren, J.H. 2003.
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• Watkins, C.B. and Miller, W.B. 2005. A summary of physiological
processes or disorders in fruits, vegetables and ornamental products that are
delayed or decreased, increased, or unaffected by application of 1methylcyclopropene (1-MCP). Available online at:
• http://www.hort.cornell.edu/mcp/ethylene.pdf
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