Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

Подождите немного. Документ загружается.

Design of Storage Areas

0028 Fruits and vegetables can be stored in a CA most

effectively in special chambers. These chambers are

equipped with a cooling system, devices for creating

the necessary gas composition, and devices for con-

trolling and regulating relative humidity. A number

of factors should be considered carefully before the

construction of any storage facility. These factors

include: site selection, integrity of the structure, insu-

lation, vapor barriers, an appropriate refrigeration

system, adequate temperature- and gas-monitoring

system, and good storage facility layout.

Volume Planning Decisions

0029 The requirements that should be kept in mind before

planning for storage chambers are the level of pro-

duce loading that can be expected, the distribution of

temperature and gases in the mass of produce, and the

geometry and parameters of the chambers. If the

chambers have very high loads, it will be difficult to

obtain a gas mixture of the required composition to

maintain CA. It has been shown that produce must be

loaded in a continuous stack with a minimum gap

between them and the walls. For instance, in the UK,

the standard distance between boxes in the stack is

0.5 cm. When loading containers in the chambers, the

gap between them is 2.5 cm; in the case of boxes on

racks, the gap between them is 5 cm. In all cases, the

gap between the stack of produce and the enclosure

wall is 2.5 cm. At the same time, it must be considered

that these chambers should be economical. Studies in

the former USSR have shown that from the viewpoint

of minimum costs of enclosures, chambers with a

height up to 5.4 m are considered economical. In

other countries, this value is 4.0–4.8 m (UK) and

5.6–6.6 m (USA, Italy, France).

0030 Modern CA fruit storage areas consist of individual

chambers with load capacities of 50–150 tonnes, or

more. Volume planning designs regarding these

chambers are generally made on the basis of various

considerations, which are summarized in Table 1.

Hermetic Sealing and Gas Insulation

0031To maintain the desired gas mixtures, chambers

should be airtight, and because of the cost of airtight

insulation of partition walls, these chambers should

not be very high. One of the most common materials

used for sealing is foamed-in-place polyurethane,

which should be protected by a fire-resistant thermal

barrier. Another important factor is the selection of

the gas-impermeable material used for the construc-

tion of the chambers. The most reliable gas insulation

materials are galvanized iron sheets, aluminum foil

covered with asphalt on one or both sides, vinyl-

based resins, polyester and epoxy resins, reinforced

fiber glass, and asphalt matriced with rubber. Besides

these, plastic sheets, gas-impermeable varnish, paints,

etc. have also been used. Galvanized iron sheets and

aluminum foil covered with asphalt are the materials

that are used most widely in Italy, the USA, and the

UK. These barriers should prevent the build-up of

moisture within walls and ceiling.

0032The most difficult places to design in chambers

with a CA are the joints between walls, ceiling and

floors, and inlets and outlets of pipelines in the

building. One of the techniques to maintain the seal

between walls and floors is the use of continuous

monolithic foamed-in-place polyurethane. Doors

lined with galvanized iron sheets on both the inner

and outer sides have been used. Wood doors that are

sealed with epoxy coatings have also been used.

Urethane foam is usually used to insulate doors. The

cost of these insulated doors is about 11–14% of the

total cost of construction of the storage facility. Other

considerations in the design of CA storage facilities

include the installation of an observation window,

pressure relief system, and continuous leakage testing.

Research is in progress to make cold storages airtight

and more flexible. A plastic tent has been developed

for the CA storage of small quantities of fresh com-

modities. These CA tents are airtight and can be set

up easily, allowing flexibility in the use of this storage

space.

See also: Fumigants; Fungicides; Insect Pests: Insects

and Related Pests; Problems Caused by Insects and

Mites; Ripening of Fruit; Spoilage: Bacterial Spoilage;

Molds in Spoilage

Further Reading

Calderon M and Barkai-Golan R (eds) (1990) Food Preser-

vation by Modified Atmospheres. Boca Raton, FL: CRC

Press.

Eckert JW (1975) Postharvest physiology. Part 1. General

principles. In: Pantastico EB (ed.) Postharvest Physi-

ology, Handling and Utilization of Tropical and

tbl0001 Table 1 Considerations for chamber designs

Chamber design Measurements

Volume 4–5 m

tonne

1

Size Vary with the size of boxes

Net height 4.8–5.4 m

Gap 1–2 cm for boxes; 5–10 cm for trays

Minimum capacity 30–50 tonnes

Dimensions of chambers 6 6 m, 6 12 m, and 12 12 m;

with a net height of 4.8–5.4 m

1606 CONTROLLED-ATMOSPHERE STORAGE/Applications for Bulk Storage of Foodstuffs

Subtropical Fruits and Vegetables, pp. 393–394. West-

port, CT: AVI.

Eckert JW (1978) Pathological diseases of fresh fruits and

vegetables. In Hutlin HO and Milner M (eds) Posthar-

vest Biology and Biotechnology, pp. 161–209. Westport,

CT: Food and Nutrition Press.

Forbes-Smith M (1999) Induced resistance for the bio-

logical control of postharvest diseases of fruits and

vegetables. Food Australia 51: 382–385.

Kader AA (1978) Effects of adding CO to controlled atmos-

pheres. In: Weichman J (ed.) Vegetables and Postharvest

Physiology, pp. 277–284. New York: Marcel Dekker.

Kidd F and West C (1936) The Gas-storage of English-

grown Conference Pears. Report of the Food Investiga-

tion Board for 1935, p. 85. London: Her Majesty’s

Stationary Office.

Leyte JC and Forney CF (1999) Controlled atmospheres

tents for storing fresh commodities in conventional

refrigerated rooms. Hort Technology 9: 672–675.

Metlitskii EG, Sal’kova EG, Volkind NL, Bondarev VI and

Yanyuk VYA (1972) Controlled Atmosphere Storage of

Fruits, p. 150. Moscow: E’konomika.

Nilsson T (2000) Postharvest handling and storage of vege-

tables. In: Shewfelt RL and Bruckner B (eds) Fruits &

Vegetable Quality, An Integrated View, pp. 96–123.

Lancaster, PA: Technomics.

Soderstorm EL and Brandl DG (1985) Controlled atmos-

pheres to reduce post harvest insect damage to horticul-

tural crops. Proceedings of the 4th National Controlled

Atmosphere Research Council, pp. 207–212.

Yahia EM (1998) Modified and controlled atmospheres for

tropical fruits. Horticultural Reviews 22: 123–183.

Effects on Fruit and Vegetables

M V Rama and P Narasimham, Formerly of Central

Food Technological Research Institute, Mysore, India

Introduction

0001 Controlled-atmosphere storage (CAS) is one of the

most important innovations in fruit and vegetable

storage systems as the composition of gas in the

storage affects their storage life. The CAS technology

involves reduction of oxygen (O

) and increasing

carbon dioxide (CO

) as compared to the ambient

atmosphere. Sometimes it also involves removal of

ethylene and addition of carbon monoxide. CAS im-

plies continuous monitoring and precise adjustment

of these gases within the storage container, to a pre-

determined level. On the other hand, in modified-

atmosphere storage (MAS), gas composition is not

actively controlled; gas atmosphere within the pack-

age is created by the respiratory activity of the fresh

produce. Several types of whole and minimally pro-

cessed fruits and vegetables have been successfully

stored in modified-atmosphere packages. Kidd and

West originally established the scientific basis of

CAS in the early twentieth century. It has been

shown to be effective in extending the postharvest

life and quality of a wide range of fruits and vege-

tables.

0002Increasing commercial use of this technology over

recent years in both the short and long term has been

in response to market demand for the supply of all

types of fresh fruits and vegetables at all times. This

article reviews the uses of pre-CAS treatments,

physiological changes related to ripening and respir-

ation, sensory and storage quality, and poststorage

life of fresh fruits and vegetables stored in controlled

atmosphere.

Gaseous Atmosphere in Commercial Use

0003Although the original idea was to replace refriger-

ation by CAS, observations show that CAS is most

effective in combination with refrigeration, providing

additional benefits. Responses to modification in the

atmosphere vary considerably among species, organ

types, developmental stage, crop temperature, grow-

ing conditions, and the degree of ripeness before

harvest and include both undesirable and beneficial

physiological responses. Recommended controlled-

atmosphere conditions during storage for various

fruits (Table 1) and vegetables (Table 2) have been

given. Except for apple and pear, for most other fruits

and vegetables the typical controlled-atmosphere

conditions suggested have no, little, or only some

commercial use.

0004Most fruits and vegetables tolerate as low as 2%

and as high as 5–10% CO

. The commercial

adoption of CAS for a given kind of produce depends

on the balance between cost and benefits, because

control of gas composition is expensive. Table 3

gives the general effects of low O

and high CO

concentrations on fruits and vegetables.

0005In general, the lower the O

and the higher the CO

levels, the better will be the controlled-atmosphere

effects such as retardation of ripening and senescence.

However, the extent to which O

level can be reduced

and the CO

level can be elevated is limited due to the

shift from aerobic to anaerobic metabolism, which

leads to off-flavors. The incorrect application of

CAS may have detrimental effects on the crop being

stored. Sprouting and rooting problems may be trig-

gered under certain CAS conditions, as in carrot,

onion, and potato. Apple and pear are the main fruit

CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables 1607

types stored commercially under CAS at present.

Studies on other fruits and vegetables have proved

promising for its wider application.

Precontrolled Atmosphere Storage

Treatment

0006Subjecting fruits and vegetables to various types of

preCAS treatments can enhance the effectiveness

of CAS. Cooling kiwi fruit to 0.5



C immediately

after harvest reduces the incidence of rot caused by

Botrytis cinerea and increases the shelf-life during

CAS. Curing crops like potatoes, yam, sweet potato,

garlic, and onion at high temperature before they are

stored in controlled atmosphere is beneficial to en-

hance their storage life. A prestorage heat treatment

effectively controlled ‘telescoping’ of cut green

onions. Several types of pre-CAS treatments have

been suggested, especially to improve the quality of

apple varieties. Keeping Granny Smith apples at a

higher temperature of 46



C for 12 h before CAS

resulted in firmer fruits with higher soluble solids-

to-acid ratio and lower incidence of superficial scald

than fruits which were not preheat-treated. Hypoba-

ric ventilation prevents the accumulation of scald-

related volatiles in the epicuticular wax of apples,

thus preventing scald development.

0007Exposing apple, pear, and avocado fruits to high

levels of CO

shock treatment prior to CAS is shown

to be beneficial; such a treatment to golden delicious

apples resulted in better green color of the skin and

firmer flesh, with no change in titratable acidity. It

also reduced the incidence of physiological disorders

such as internal browning and mesocarp discolor-

ation in pears and avocado respectively. An initial

low O

stress (ILOS) reduces superficial scald inci-

dence during CAS of apple varieties like Law Rome

and Granny Smith. Scald development is related to

the accumulation of 6-methyl-5-hepten-2-one (MHO)

in fruits. ILOS inhibits both productions of alpha-

farnesene and its breakdown product, MHO. ILOS

is suggested to be a potential alternative for chemical

scald inhibitors.

0008Therefore, besides the application of controlled-

atmosphere technology to preserve the quality of

certain fresh fruits and vegetables, a cold and high

temperature, chemicals, low O

, or high CO

pre-

treatment for a short duration would give additional

beneficial effects in extending the storage life. Given

below are some of the significant effects of CAS on

fruits and vegetables.

Effect on Fruit Ripening

0009Studies have shown that controlled atmosphere has

its most beneficial effects on climacteric fruits at

the preclimacteric stage by prolonging this period.

The effect is less marked in climacteric fruits

at the ripening stage. The climacteric fruits are much

tbl0001 Table 1 Recommended controlled-atmosphere or modified-

atmosphere conditions during storage and transport of selected

fruits

Produce Temperature (



C) O

(%) CO

(%)

Apple

0–2 2–3 1–5

Asian pear

2 3 1–5

Avocado

10–13 2–5 3–10

Banana

12–16 2–5 2–5

Black berry

0–5 5–10 10–19

Blue berry

0–5 5–10 15–20

Cherry

0–5 3–10 10–15

Fig

0–5 5–10 15–20

Grape

0–5 2–5 1–3

Kiwi fruit

0–5 5–10 5–10

Lemon

10–15 5–10 0–10

Lime

10–15 5–10 0–10

Mango

10–15 5 5

Nectarine

0–5 1–2 3–5

Orange

5–10 5–10 0–5

Papaya

10–15 2–5 5–8

Peach

0–5 1–2 1–2

Persimmon

0–5 3–5 5–8

Pine apple

5–10 2–5 5–10

Plum

0–5 1–2 0–5

Strawberry

0–5 5–10 15–20

Tomato

8–12 1–5 0

Climacteric fruits;

nonclimacteric fruits.

Adapted from Kader AA (1992) Post Harvest Technology of Horticultural

Crops, 2nd edn. Oakland, CA, USA: Division of Agriculture and Natural

Resources and Bishop D (1996) Controlled atmosphere storage. In: Dellino

CV (ed.) Cold and Chilled Storage Technology. London: Blackie.

tbl0002 Table 2 Recommended controlled-atmosphere or modified-

atmosphere conditions during storage and transport of selected

vegetables

Produce Temperature (



C) O

(%) CO

(%)

Beetroot 0 10 3

Broccoli 0–5 1–2 5–10

Brussels sprout 0–5 1–2 5–7

Cabbage 0–5 2–3 3–6

Capsicum 8–12 3–5 0

Cauliflower 0–5 2–5 2–5

Chilli 8–12 3–5 0

Cucumber 8–12 3–5 0

Celery 0.5 1–4 0–5

Lettuce 0–5 2–5 0

Okra 8–10 3–5 0

Onion 0 3 5

Parsely 0–5 8–10 8–10

Spinach 0–5 21 10–20

Sweet potato 0–5 2–4 5–10

Adapted from Kader AA (1992) Post Harvest Technology of Horticultural

Crops, 2nd edn. Oakland, CA, USA: Division of Agriculture and Natural

Resources and Bishop D (1996) Controlled atmosphere storage. In: Dellino

CV (ed.) Cold and Chilled Storage Technology. London: Blackie.

1608 CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables

sensitive to ethylene (C

), hence its removal is

particularly recommended for long-term storage.

CAS inhibits the production of C

by the fruit,

which is due to the absence of sufficient oxygen. In

Jonathan and Elstar apples, increased CO

concen-

tration reduced the activity of ethylene; similar re-

duced ethylene activity is reported in kiwi fruits and

mission figs. The activity of several oxygen-requiring

enzymes related to fruit ripening is reduced in CAS. In

bananas, although low oxygen levels (1–15%) in

store induce ripening, the degreening process of the

peel is inhibited. The fruit in which the ripening pro-

cess is initiated is slowed down in a low-oxygen at-

mosphere. Holding mature green tomatoes in low O

atmosphere delayed the decrease in cell wall galacto-

syl residues and increased soluble galactose levels,

thus causing delayed loss of fruit firmness; this change

was associated with increased development of red

color, respiration, and ethylene production. So it is

suggested that cell wall-related ripening processes are

either ethylene-dependent or require only low base-

line ethylene levels to occur.

Effect on Respiration

Effect of Low O

0010 For some fruits and vegetables, depending on the

temperature, the respiration rate is lowered during

storage in 3% O

. When the O

concentration of

the storage atmosphere is reduced below 8% in par-

ticular, the respiration rate decreases as a function of

the O

concentration (Figure 1). Anaerobic respir-

ation is initiated in the tissue as the O

concentration

drops to the extinction point. Anaerobic respiration

becomes predominant, with a further decrease in the

concentration of O

, and the CO

output starts to

increase after it reaches its lowest value at the critical

concentration. Further reduction in O

concen-

tration below the critical point brings a shift in the

respiratory metabolism; pyruvic acid, the end product

of glycolysis, is no longer oxidized through Kreb’s

cycle, but is converted into acetaldehyde, CO

,and

finally ethanol. This causes tissue breakdown and

development of off-flavor. Thus the minimum con-

centration of O

necessary to continue aerobic respir-

ation and prevent fermentation will be optimum for

the storage atmosphere. This concentration is usually

2–5%, and depends on the kind of produce, tempera-

ture, and the duration of storage. Carrot shreds under

low O

atmosphere exhibited an increase in respira-

tory quotient (RQ), an accumulation of fructose 1,6-

biphosphate, coupled with an increase in the activity

of phosphofructokinase (PFK). This suggests the in-

volvement of PFK in the regulation of glycolysis

under low O

atmosphere.

0011The decrease in O

uptake under reduced levels of

in the atmosphere is due to the decrease in the

tbl0003 Table 3 General effects of low oxygen and high carbon dioxide concentrations on fruits and vegetables

Effectsof low oxygen Effects ofhigh carbondioxide

Reduced respiration rate and substrate oxidation Decreased synthetic reactions in climacteric fruit

Delayed ripening of climacteric fruit and breakdown of

chlorophyl

Delaying the initiation of ripening and inhibition of

chlorophyl breakdown

Prolonged storage life Inhibition of some enzymatic reactions

Reduced rate of ethylene production and degradation of

soluble pectins

Altered metabolism of some organic acids; production of

off-flavors

Formation of undesirable flavor and odors with

altered texture

Induction of physiological disorders and reduced fungal growth

on the crop

Development of physiological disorder Inhibition of the effect of ethylene

Retention of tenderness and decreased discoloration levels

Changes in sugar content and effects on sprouting, as in potatoes

output

uptake

05101520

Oxygen (%)

Relative respiration

fig0001Figure 1 Schematic diagram showing the effect of O

concen-

tration on the uptake of O

and evolution of CO

in fruits and

vegetables. E, Extinction point (the lowest O

concentration at

which aerobic respiration stops); C, critical O

concentration (the

concentration of O

at which CO

produced is lowest).

CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables 1609

activity of oxidases like polyphenol oxidase, ascorbic

acid oxidase, and glycolic acid oxidase, and not due

to the reduction in the activity of cytochrome oxidase.

The storage atmosphere must contain less than 2%

for cytochrome oxidase to be affected; on the

other hand, the affinity for other oxidases to O

20 times more than that of cytochrome oxidase. The

increased activity of enzymes like pyruvate decarbox-

ylase and alcohol dehydrogenase is not responsible

for the initiation of the fermentation process; these

enzymes are mostly active even before exposure to

low O

levels.

0012 The beneficial effects of low-O

atmosphere are

also related to the biosynthesis and action of C

under the established controlled atmosphere, as it is

directly related to ripening and senescence processes.

is produced by the oxidation of 1-aminocyclo-

propane-1-carboxylic acid (ACC) by ACC oxidase

(Eqn (1)):

1-aminocyclopropane-l-carboxylic acid

! C

þ CO

þ HCN þ H

ð1Þ

The concentration of O

that gives half the maximum

production rate ranges between 5% and 7% in

various tissues, so that 2–5% atmosphere, usually

used in CAS, directly interferes with C

synthesis.

The action of C

on plant tissues at 3% O

is only

about 50% of that in the air.

Effect of High CO

0013 High CO

atmosphere affects several processes,

including respiration rate, ethylene production,

ripening and senescence, and acidity of the produce.

0014 Respiration rate The respiration response to high

levels of CO

depends upon the crop, cultivar, and

the stage of development. Under similar CAS condi-

tions the suppression of respiration was more in

golden delicious apples than in Cox’s orange pippin

apples. In a study on the effect of elevated levels of

on respiration and ethylene production, changes

in respiration seldom coincided with changes in C

production. Respiration rate decreased in ripening

banana, pink tomato, and pickling cucumber, while

it increased up to 30% in potatoes and carrots, and

had no effect on the respiration in guava, orange, and

onion bulbs. Ethylene evolution was substantially

reduced at all levels of CO

in guavas and tomatoes,

while it was accelerated in bananas, carrots, cucum-

bers, onions and potatoes, which is possibly due to an

early injury response.

0015 Studies in pears have shown that high CO

atmos-

phere affects the glycolytic intermediates and

enzymes; inhibition in the activity of phosphofru-

ctokinase, a key enzyme of glycolysis, resulted in

the accumulation of fructose-6-phosphate and de-

crease in fructose-1,6-diphosphate, in contrast to the

effect of low O

. Accumulation of succinic acid, an

intermediate of Kreb’s cycle, has been observed in

several crops, such as apples, pears, lettuce, podded

pea, and activity of succinic dehydrogenase in peas

under high CO

levels. The oxidation of several inter-

mediates of the Kreb’s cycle is suppressed, as revealed

in studies of isolated mitochondria from apples. For-

mation of ethanol and aldehyde is common in many

crops, under high CO

atmosphere, despite the pres-

ence of sufficient O

; this phenomenon is called CO

zymasis.

0016Ethylene production A reduction in the O

uptake in

climacteric fruits such as banana and avocado, with-

out affecting the respiration activity before climac-

teric, has been observed under high CO

atmosphere;

also the onset of climacteric rise, which is triggered by

endogenous ethylene, is delayed. These results suggest

that a high CO

atmosphere delays the burst of ethyl-

ene (C

). In most vegetables and nonclimacteric

fruits like citrus, grapes, and Japanese pears, O

uptake is not affected under high CO

atmosphere.

However a depression in the O

uptake occurs in

ripening climacteric fruits and broccoli, accompanied

by inhibition of C

synthesis. On the other hand,

10% or more CO

in the storage atmosphere, in crops

like lettuce, cucumber, and lemon, which are suscep-

tible to high CO

level, resulted in the elevation of O

uptake with induction of C

synthesis. These obser-

vations indicate that the respiratory response of crops

to high CO

levels might be mediated mainly by the

effect of CO

on the synthesis or action, or both, of

. In other words, retardation of ripening or sen-

escence and the associated biochemical and physio-

logical changes are caused by concentrations on

action or synthesis of C

rather than on any direct

effect on the respiratory metabolism. Tomatoes at

breaker stage under CAS showed a reduced natural

ethylene production rate and delayed increase in galac-

tosidase activity. Such effects remained unchanged by

the addition of exogenous ethylene. These results sug-

gest that ethylene-mediated responses are impaired

by low O

and high CO

and that exogenous ethylene

and low O

/high CO

concentrations are acting anta-

gonistically.

0017Results of a study on ethylene biosynthesis in Jona-

than apple fruits immediately after removal from

CAS conditions (0–2% CO

with O

of 3% or 15%

concentrations at 0



C) included inhibition of C

production, decrease in the concentration of ACC,

increased accumulation of ACC under low O

, but

1610 CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables

only in the absence of CO

, and decrease in the activ-

ity of C

forming enzyme at 20% CO

at both the

concentrations. By these results, inhibition of

ethylene production has been attributed to the inhibi-

tory effect of CO

on ACC synthase activity.

0018 Similar results are reported on other apple cultivars

like Barnack and Beauty. In kiwi fruits, high CO

re-

duced ethylene production and ACC oxidase activity.

Added to this, several responses of crops to ethylene

such as fruit ripening, abscission, growth inhibition,

floral senescence, and the induction of some enzymes,

are delayed or prevented in high CO

atmosphere.

0019 A comprehensive study of the effect of CO

reversing the action of C

in growth of pea seg-

ments has suggested that CO

competes with C

for binding site, and the relative affinity of the site for

15% CO

is equivalent to that for 1 p.p.m. C

However, the calculation of the binding site with

radioactive C

suggests that the inhibition of

binding is indirect or due to secondary effects

such as pH changes.

0020 Acidity and pH CO

dissolves easily in plant tissues,

forming carbonic acid, which dissociates into bicar-

bonate and hydrogen ions. Hence the general assump-

tion is that tissues exposed to high CO

levels would

have low pH. However, the reported measurements

of pH changes in several plant tissues stored in

high CO

atmosphere have been contradictory.

Intact lettuce tissues exposed to 15% CO

for 6

days showed a drop of about 0.4–0.1 pH in the

cytoplasm and vacuoles respectively. Juice extracted

from a crop exposed to high CO

has shown in-

creased pH. As alterations in the pH of plant

cells might affect the metabolic activities, the change

in pH due to CO

could be treated as both beneficial

and harmful effects of high CO

condition for the

harvested crops.

Effects on Sensory Quality

Flavor and volatile compounds

0021 Factors like volatile compounds, organic acids,

carbohydrates, and phenolics affect the flavor of fruits

and vegetables. Flavor determines the eating quality

of the produce. Controlled-atmosphere-stored fruits

are known to retain good flavor longer than fruits just

cold or air-stored, as in kiwi fruits, Russian pears, and

tomatoes. For golden delicious apples, CAS has

proved best in terms of flavor maintenance. The con-

trolled-atmosphere-stored white cabbages had a fresh

peppery flavor and rated higher in flavor quality than

corresponding air-stored samples. On the other hand,

the flavor quality was inferior in limes and apricots

stored in controlled atmosphere. The low O

of 3 kPa

is reported to be enough to induce reduction in pear

aroma compounds; the decadienote moiety appeared

to have been more affected than methyl or ethyl

moieties. The accumulation of amino acids and re-

duction in fatty acids and aroma compounds in Fuji

apples stored under low O

atmosphere indicates that

a change in the aroma production involves altering

fatty acid and amino acid metabolisms.

0022Controlled atmosphere will affect the production

of characteristic volatile compounds, which give

flavor and aroma to fruit and vegetables. The produc-

tion of volatile compounds is not only suppressed

during CAS, as in several apple varieties, but the fruits

fail to synthesize normal amounts even after removal

from the CAS. The highest volatile emission from

Granny Smith apples was after 5 months of CAS

and it was highest under low-oxygen (LO) and ultra-

low-oxygen (ULO) atmospheres. LO and ULO form

valuable technologies for maintaining the sensorial

quality of apple.

Development of Off-Flavor

0023The unfavorable concentrations of O

and CO

in the

storage atmosphere, especially for a long time, result

in the development of off-flavors and off-tastes in

fruits and vegetables and are generally attributed to

shift from aerobic to anaerobic respiration. In intact

lettuce heads exposed to 20% CO

, the development

of off-flavor is related to the production of ethanol

and acetaldehyde. More than 15% CO

induces

odors in broccoli and cauliflower. In fruits like

Granny Smith, yellow Newton apples, twentieth-

century pear, and Angellena plums and peaches,

ULO of 0.02–0.25% resulted in the development of

alcoholic of-flavor. Sweet potatoes stored in 2% O

develop off-flavor with reduced sweet-potato flavor.

Controlled-atmosphere-stored strawberries do not

develop visible injury: the juice develops off-flavors,

which are correlated to the accumulation of ethanol

and ethyl acetate and acetaldehyde.

0024In contrast, avocados stored in air had higher etha-

nol and acetaldehyde content than those stored in

CAS. One of the findings on the biogenesis of off-

odor in broccoli under LO atmosphere suggests that

broccoli has the enzymic capacity to convert free

sulfur-containing amino acids into volatile sulfur

compounds, which contribute to the objectionable

odor. The precursors of such volatiles, free sulfur-

containing amino acids, are synthesized, preferably

in broccoli that is stored under LO atmosphere.

Ascorbic Acid and Acidity

0025The concentration of ascorbic acid in fruits and vege-

tables can be affected by storage conditions and is

CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables 1611

important from the nutritional point of view. The loss

of ascorbic acid is hastened in tomatoes when stored

in high CO

atmosphere. Similar effects are reported

in strawberries and blackberries, where the loss of

ascorbic acid increases with increase in CO

. In Chi-

nese cabbage loss of ascorbic acid took place at 30–

40% CO

levels. Though in general higher CO

(> 5%) content has the tendency to reduce ascorbic

acid levels, it depends on the type of produce, storage

temperature, and the concentration of CO

. For

example, the degradation of ascorbic acid in parsley

leaves is retarded with storage in 4.2% O

and 1%

compared with air storage, but it is accelerated

with storage in 4.2% O

and 6% CO

. A LO atmos-

phere is favorable to the retention of ascorbic acid

because of the low affinity of ascorbic acid oxidase

to O

. Pineapple stored in atmosphere containing

less than 5.4% O

retained higher ascorbic acid con-

tent, with no effect on total soluble solids (Figure 2).

The storage temperature during CAS affects the

ascorbic acid content; CAS treatment at 12



resulted in lower ascorbic acid retention, while

there was no effect at 1



C in okra. Pears showed a

decline in ascorbic acid concentration at enhanced

levels of CO

0026The organic acids, especially malic acid, of apples

are retained better if favorable controlled-atmosphere

conditions are reached quickly. However, if the CO

level reaches 3%, loss of acidity is sometimes stimu-

lated in these fruits. A significant amount of acidity is

lost in Valencia oranges stored in controlled atmos-

phere. In tomatoes the titratable acidity increased

during the first 20 days of CAS at 13



C and it tended

to decrease during further storage (Figure 3). Vege-

tables such as lettuce, spinach, and broccoli always

contain higher amounts of titratable acid after stor-

age in air than after storage in controlled atmosphere.

Texture and Color

0027Due to delay in ripening under CAS, normally a de-

sirable texture is maintained for several fruit types

like apple, pears, peaches, apricots, and tomatoes.

Retention of firmness is one of the most important

advantages of the commercial CAS of apples. Though

both high CO

and low O

contribute to the retention

of flesh firmness, the effect of high CO

is more

prominent than that of low O

. Induction of enzyme

polygalacturonase, which degrades pectic substances,

is prevented when mature green tomatoes are stored

in 5% CO

and 5% O

for up to 8 weeks at 12.5



on removal of tomatoes from such an atmosphere to

air, fruit softening is resumed due to the synthesis of

polygalacturonase. In kiwi fruit, retention of fruit

firmness is better in CAS, but presence of even low

concentrations of C

would counteract this

positive effect. The texture of most other fruits and

2345

Controlled-atmosphere

storage conditions

Ascorbic acid (mg 100 ml

−1

) Brix

fig0002 Figure 2 Effect of various controlled-atmosphere storage con-

ditions on ascorbic acid (open columns) and total soluble solids

(filled columns) of pineapple stored at 8



C for 3 weeks and for 5

days at 20



C. 1, 1.3% O

þ0% CO

; 2, 1.4% O

þ11.2% CO

;

3, 2.2% O

þ0% CO

; 4, 2.3% O

þ11.2% CO

; 5, 5.4% O

þ0%

. Adapted from Haruenkit R and Thompson AK (1996) Effect of

and CO

levels on the internal browning and composition of

pineapples Smooth Cayenne. In: Proceedings of the International

Conference on Tropical Fruits, pp. 343–350. Kuala Lumpur,

Malaysia.

0.40

0.35

0.30

0.25

0.20

0 102030405060

Storage time (days)

Titratable acidity (%)

fig0003Figure 3 Changes in the titratable acidity of mature green

tomatoes stored under different controlled-atmosphere storage

conditions for 60 days at 13



C (all treatments with 5.5% O

Circles, control; squares, 3.2% CO

; triangles, 6.4% CO

;

diamonds, 9.1% CO

. Adapted from Batu A (1995) Controlled At-

mosphere Storage of Tomatoes. PhD thesis. Cranfield Uni-

versity, UK.

1612 CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables

vegetables is little influenced by LO conditions. The

positive effects of high CO

conditions reported in-

clude delay in the softening rate of strawberries and

bush-type berries, reduced splitting in bitter gourd,

and the retardation of the toughening of asparagus

spears, cauliflower, and snap beans, and retention of

bright yellow color and firmness in star fruits.

0028 The reduced rate of chlorophyl breakdown

under controlled-atmosphere conditions improves

the retention of green color of the produce. High

concentration in particular preserves the chlor-

ophyl content. Such an effect is obvious in green

vegetables like spinach, asparagus spears, broccoli,

snap beans, green limes, and cabbage. Some of the

winter white cabbage cultivars retained better green

color and crisp texture when stored at 0–2



C under

controlled atmosphere, consisting of 5–6% CO

and

3% O

. The degradation of chlorophyl and the syn-

thesis of pigment such as lycopene, carotene, and

xanthophyl are suppressed when tomatoes are stored

in 5% O

anda5%CO

mixture; biosynthesis

of anthocyanin is slowed down in plums under

controlled-atmosphere conditions. Bitter gourd fruits

stored for 3 weeks in controlled atmosphere (2–5%

with 3.5–5% CO

) had greater retention of

green color. In spinach stored under low O

atmos-

phere (0.8%), the color and chlorophyl content

were not affected. The extinction point of spinach is

found to be > 0.4% but < 0.2% O

, indicating that

spinach can also be stored under LO atmosphere

without quality loss due to anoxia. Bell peppers

stored under LO showed slower rate of decrease in

green color.

Controlled Atmosphere and Storage

Disorders

Diseases and Pests

0029 The process of ripening and senescence in climacteric

fruits renders them susceptible to infections by patho-

gens. The delayed ripening and senescence in such

fruits by storing them in controlled atmosphere

allows them to retain greater resistance to postharvest

diseases; thus CAS can reduce disease development in

crops by improving their physiological conditions.

When exposure time is short, some horticultural

crops might be tolerant of more extreme controlled-

atmosphere conditions such as <1% O

and > 20%

than are normally used. Such ULO and high

levels are fungistatic, directly suppressing fungal

growth and spore germination. High CO

retards

fungal decay incidence on cherry, blackberry, rasp-

berry, strawberry, fig, nectarine, and grape. The

reduction in disease levels in tomatoes is chiefly due

to LO levels with a little additional effect from

increased CO

levels. LO and high CO

levels, at

temperatures less than 10



C, reduce the infection of

potatoes by Erwinia caratovora. On the other hand,

anaerobic conditions created around freshly har-

vested or uncured potatoes during storage or trans-

port prevent the formation of wound periderm and

the oxidation of phenolic compounds, both of which

are involved in the defense mechanism against bacter-

ial infections; the depletion of O

rather than increase

in CO

in the atmosphere would increase the roting

by both Erwinia and Clostridium.

0030The postharvest pathogen of apple fruits Penicil-

lium expansum can be better controlled in controlled-

atmosphere conditions; its biocontrol agent Candida

sake has the better ability to colonize under con-

trolled-atmosphere conditions, on the apple fruit

surface and in wound tissues, thus protecting apples

completely from damage by the growth of P. expan-

sum. The incidence of rots caused by Botrytis cinerea

in white cabbages was reduced to a greater extent

under storage atmosphere containing 5–6% CO

and 3% O

; it also reduced or eliminated the inci-

dence of pepper-spotting, a type of nonmicrobial leaf

necrotic disorder common to cabbages.

0031Extreme controlled-atmosphere conditions are

insecticidal too. For example, CAS is commonly

used in Mexico to reduce the incidence of insect

infestation of Manila mango fruits; these fruits can

tolerate controlled-atmosphere treatment at tempera-

tures < 44



C. Fig moth (Cadra cautella) could be

controlled when dried figs were stored under con-

trolled-atmosphere conditions (1% O

with 10–

15% CO

). A short-term insecticidal controlled at-

mosphere (ICA) containing 40% CO

and 0.25% O

is shown to be a promising alternative to methyl

bromide fumigation for Fuyu persimmons without

affecting the marketability of fruits. A CO

concen-

tration of 50% is shown to control insects in other

tropical fruits like avocado, papaya, and mango.

Physiological Disorders

0032It is necessary to achieve and maintain precise gas

mixtures during CAS, which otherwise may cause

irrevocable damages to fruits and vegetables in the

form of physiological disorders and injuries (Table 4).

The preharvest factors like maturity at harvest, stor-

age season and locality, and size of the fruit are also

the factors determining the incidence of CAS dis-

orders. The flesh breakdown injury and internal

browning in pear fruits under CAS are associated

with the production of acetaldehyde, ethanol, and

ethyl acetate and stimulation of free radicals respect-

ively, in the stored fruits. ULO of 0.5% induced a

reddish discoloration in Brussels sprouts and an

CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables 1613

extremely bitter flavor in nongreen portions of the

sprouts.

0033 The browning of core tissue that is triggered in

conference pears is related to decreased ascorbic acid

concentration under enhanced CO

levels. Pears that

show browning produce ethane, which is said to be

probably a result of membrane peroxidation.

0034 Some recent tests have shown that apples, when

stored under controlled-atmosphere conditions early

after harvest, are more susceptible to CO

injury like

internal browning, flesh softening, and core

browning. Incidence of Braebun browning disorder

(BBD), a type of CO

injury in late-harvested Braebun

apples, increases with decrease in the level of O

the storage atmosphere. Small-sized Fuji apples were

less susceptible to CAS disorder than large fruits.

Delaying storing apple fruits in controlled atmos-

phere or CO

accumulation is recommended as it

may reduce the incidence and severity of all the

above-mentioned physiological disorders.

0035 The appearance of CO

injury symptoms is shown

to be a function of concentration, exposure time, and

temperature, while injury under low O

levels is

due to anaerobic respiration which results in the

accumulation of toxic byproducts like alcohol and

acetaldehyde. On the other hand, certain types of

physiological disorders can be curtailed under CAS.

For example, a LO of > 5% reduces the brown discol-

oration of beans which usually develops during har-

vesting and handling. High CO

is reported to inhibit

browning in snap beans at the site of mechanical

injury and skin browning in lichee fruit.

0036 A hypothesis to explain the mode of action of LO

and high CO

on the incidence of physiological dis-

order, such as browning, has been proposed based

on a recent study on the effects of CAS conditions

on adenosine triphosphate (ATP) and adenosine

diphosphate (ADP) levels and the concentrations of

NAD(H) and NADP(H) in apple varieties stored. The

reduced ATP level and increase in the accumulation of

fermentative products might indirectly change the

mitochondrial membrane permeability and the elec-

trochemical potential. Alterations in the membrane

permeability leads to leakage of ions, protons, acids,

and phenolics from vacuoles, causing acidification

and oxidation of phenols in the cytoplasm and finally

the browning of tissues.

Residual Effects of CAS

0037Storing fruits and vegetables in CAS can affect their

subsequent shelf-life. For example, bell pepper fruits

exhibited suppressed CO

production and O

con-

sumption for at least 24 h after transfer to air. The

residual respiratory inhibition in bell peppers is

found to be due to a reduction in the mitochondrial

oxidative capacity and not due to changes in the ultra-

structure of mitochondria. Black raspberry (cv. Bris-

tol) showed greatest weight loss after removal from

controlled atmosphere. Several potato cultivars

showed complete sprout inhibition, low weight loss,

and healthy skin post CAS. With regard to root quality

during long-term storage and poststorage processing

potential, CAS of LO and high CO

has been shown to

be an effective method for Lance Asian bell roots. In

controlled-atmosphere-stored cabbages, storage and

trimming weight losses were lower; recoveries of

trimmed cabbages suitable for marketing or process-

ing were higher – up to 22% than in those stored in air.

0038Though the present literature is ambivalent as

regards the quality and rate of deterioration of fruit

and vegetables after they have been removed from

tbl0004 Table 4 Threshold level of O

and CO

required for causing injury to some fruits and vegetables and typical injury symptoms

Crop and cultivar CO

injury level CO

injury symptoms O

injury level O

injury symptoms

Apple, cox’s orange pippin > 1% Core browning <1% Alcoholic taste

Apple, golden delicious >5% CO

injury <1% Alcoholic taint

Apple, Elstar >2% CO

injury <2% Core flush

Apple, Jonathan >5% Flesh browning <1% Alcoholic taint, core browning

Apricot >5% Loss of flavor, flesh browning <1% Off-flavor

Avocado >15% Skin browning, off-flavor <1% Internal flesh breakdown

Broccoli >15% Off-odor <0.5% Off-odor

Cabbage >10% Discoloration of inner leaves <2% Off-flavor

Cucumber >5% Increased softening <1% Off-odors

Lettuce >2% Brown stain <1% Breakdown at center

Kiwi fruit >7% Internal breakdown <1% Off-flavor

Mango >10% Softening, off-flavor <2% Grayish flesh, skin discoloration

Pepper, bell >5% Internal browning and softening <2% Off-odors and breakdown

Strawberry >25% Off-flavor, brown discoloration <2% Off-flavor

Tomato, mature green >2% Discoloration, uneven ripening <2% Off-flavor

Adapted from Thompson AK (1998) Controlled Atmosphere Storage of Fruits and Vegetables. New York: CAB International.

1614 CONTROLLED-ATMOSPHERE STORAGE/Effects on Fruit and Vegetables

CAS, many reports indicate that the storage life is

adequate for marketing, and sometimes the market-

able life is even better than harvested produce.

Storage of Minimally Processed Fruits and

Vegetables

0039 The preference by consumers for vegetables in a

‘ready-to-cook’ and ‘ready-to-eat’ convenient form

has resulted in the supply of fruits and vegetables in

minimally processed form (peeled, sliced, diced, shred-

ded, and topped vegetables) to the market. Such min-

imally processed (MP) produce has been successfully

stored in modified-atmosphere packages (MAP) with

little or no loss in their sensory, nutritional, and market

quality. MAP using polypropylene bags with micro-

perforations has been shown to be an effective method

for storing MP fruits and vegetables. LO atmosphere is

used to control spoilage microorganisms on cut spin-

ach leaves for at least 7 days. A high level of O

inhibits

undesirable fermentation reactions, delays browning

during processing, and inhibits microbial growth

during the storage of MP fruits and vegetables in

sealed packs. MAP has been used commercially to

extend the shelf-life of minimally processed mango

and other salad vegetables and leaves.

See also: Acids: Properties and Determination; Natural

Acids and Acidulants; Apples; Ascorbic Acid: Properties

and Determination; Avocados; Controlled-atmosphere

Storage: Applications for Bulk Storage of Foodstuffs;

Flavor (Flavour) Compounds: Structures and

Characteristics; Production Methods; Pears; pH –

Principles and Measurement; Ripening of Fruit;

Sensory Evaluation: Texture; Taste