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

Подождите немного. Документ загружается.

0013 Although many countries have banned the use of

DDT, it is still of value in controlling diseases such as

malaria. Milk from cattle reared in areas where DDT

was used in agriculture can be heavily contaminated

(e.g., over 500 p.p.m.). High levels can also be found

in mild products, e.g., ghee, butter, cheese, and infant

formula. Hexachlorocyclohexanes, e.g., lindane, have

also been identified in milk after feed prepared from

sprayed crops had been given to cattle, or insecticidal

ointment had been applied directly to their skin. Some

organochlorine compounds originally unconnected to

agricultural use have accumulated in foods because of

their long-term persistence, e.g., fish containing

mirex, an ant poison and also a fire retardant in house-

hold materials. Dioxin, a byproduct of defoliant

Agent Orange, waste incineration, and industrial pro-

cesses is found widely in the environment, although

usually at low concentrations. As a result of an indus-

trial accident 25 years ago in Italy, the long-term

impact of dioxin is being examined; one effect is a

reduction in the number of male births. In 1999 in

Belgium, chickens and other food-producing animals

ingesting dioxin-contaminated feed cost the Belgian

economy more than $750 million. Motor oil contain-

ing the dioxin entered the food chain after being mixed

with vegetable oils used in the feed manufacture.

0014 Many organochlorine pesticides have been linked

to hormone disruption and reproductive problems in

aquatic invertebrates, fish, birds, and mammals. They

degrade slowly and, being fat-soluble, accumulate in

the food chain, eventually ending up in body fat. The

long-term effects of organochlorine compounds on

human beings are not yet known.

Organophosphates

0015 Organophosphates are irreversible cholinesterase in-

hibitors and can cause changes in the immune system.

Some are highly toxic and are responsible for more

accidental pesticide poisonings than any other class of

pesticides. Symptoms may be reversed with atropine

treatment. They are relatively inexpensive and con-

trol a variety of insects. Examples are parathion,

malathion, and diazinon. They are widely used on

food crops, in residential and commercial buildings

and for ornamental plants and lawn care, which

means that many people may be regularly exposed

to them. Although they do not persist in the environ-

ment, residues have been found in fruits and

vegetables. There is no known health risk from con-

sumption of this kind of uncooked food containing

low residues over a long period of time.

Carbamates

0016 Carbamates are insecticides, fungicides, herbicides,

and nematocides. These act in a similar manner to

the organophosphates for insecticides and nemato-

cides by inhibiting acetylcholinesterase, except that

the action is more rapidly reversible. The toxicity is

generally low, with the exception of a few com-

pounds, particularly aldicarb. They are considered

to be nonresidual and generally break down more

rapidly than chlorinated hydrocarbons. Aldicarb has

been absorbed from the soil by plants with leaves and

fruit accumulating the chemical. Watermelons grown

on previously contaminated soil, and hydroponically

grown cucumbers treated with aldicarb have caused

anticholinesterase symptoms in several hundred

persons in outbreaks in North America. Symptoms

of acute carbamate poisoning are the same as for

organophosphate poisoning; abdominal pain, nausea

and/or vomiting, diarrhea, muscular weakness, twit-

ching, blurred vision, watery eyes, pinpoint pupils,

excess salivation, sweating, seizures, disorientation,

and excitation.

Pyrethrins and other Botanicals

0017Botanicals are substances that are naturally produced

by plants that are poisonous to pests that prey on

those plants. Pyrethrins are derived from plants and,

together with their synthetic analogs, are used as

insecticides. Pyrethroids affect the nervous system

and are neurotoxic. Insects become disoriented, and

body functions fail, but pyrethroids do not affect

mammals because they do not penetrate mammalian

skin, and they have esterases than can detoxify the

chemical. Although these are generally safe for mam-

mals, they can be toxic to aquatic life. Strychnine,

neem, and rotenone are examples of other botanicals

that can be used against pests.

Other Pesticides

0018Alkyl mercury salts, used as fungicides on seed grain,

have caused human illness either through direct con-

sumption of the grain or through meat from pigs

eating the contaminated grain but are no longer

used in most countries. Other chemicals considered

too dangerous today and banned in many countries

are the thallium salts formerly used as rodenticides.

Bromide fumigants, such as methylbromide, are used

against insects, nematodes, viruses, weeds, and fungi

and are applied directly to the soil. Crops planted on

these soils, particularly lettuce, celery, tomatoes, cu-

cumbers, and strawberries, may accumulate bromine.

When dibromoethane was found in flour and cake

mixes arising from fumigation of wheat during stor-

age, its use was banned because of its mutagenic,

carcinogenic, and teratogenic properties. Other fumi-

gants are methylene chloride, carbon tetrachloride,

chloropicrin, phosphine, and ethylene dibromide

1596 CONTAMINATION OF FOOD

(banned). (See Fumigants.) Alar, a plant-growth regu-

lator, penetrates fruits, cannot be removed by wash-

ing or peeling, and can be converted to products that

may be carcinogenic in cooked fruit or products.

Controversy that arose regarding its potential car-

cinogenicity led to its removal from use by the manu-

facturer.

Pesticide Contaminants

0019 In addition to pesticides themselves, certain impur-

ities in formulations can be toxic. Acute delayed toxic

effects, including weight loss and pneumonia, have

developed from exposure to trimethylphosphorothio-

ate present in malathion sprays. The potential car-

cinogen nitrosodimethylamine has been found as a

contaminant in certain pesticides. Improved pesticide

production practices have since reduced the level of

these toxic impurities. (See Nitrosamines.)

Herbicides

0020 After 50 years of use, 2,4-D of the phenoxy family of

herbicides, is the most widely used herbicide world-

wide. Its major uses in agriculture are on wheat and

small grains, sorghum, corn, rice, sugar cane, soy-

beans, low-till rangeland, and pasture. It is also used

on rights of way, roadsides, noncrop areas, forestry,

lawns, turfs, and aquatic weeds. There are moves to

restrict its applications, even though no scientifically

documented health risks, either acute or chronic,

exist from approved uses. Atrazine, a triazine herbi-

cide used to control broadleaf and grassy weeds

in corn, sorghum, soybeans, sugarcane, pineapple,

Christmas trees, and other crops, also has a low

toxicity, but animal studies indicate its potential for

endocrine disruption and carcinogenicity. In contrast

to most herbicides, paraquat, a bipyridyl contact

herbicide, is highly toxic through dermal exposure

and ingestion, and must be handled with care. Some

weeds are developing herbicide resistance, and either

new compounds or new approaches may be required

for use of herbicides in the future.

Summary

0021 Several pesticides are considered potentially carcino-

genic or teratogenic based on various tests including

animal studies. However, human data are limited

(except for arsenic and perhaps for the use of the

defoliant Agent Orange in Vietnam), and there is

no epidemiological evidence that any pesticide is a

human mutagen, carcinogen, or teratogen at normal

exposure levels. Future work needs to concentrate on

mechanisms of pesticide toxicity and metabolism,

reevaluation of acceptable limits, and their control

in the environment. The use of pesticides will not be

eliminated in the future, but their use may be reduced,

and safer compounds will replace the more toxic and

persistent compounds; unfortunately, DDT and other

organochlorines will remain in the environment for

many years.

Toxic Metals

0022The sources of toxic metals are atmospheric contam-

ination, sewage sludge, trace contaminants in animal

feed, fertilizers, or pesticides. Contamination may

also occur during processing, home cooking, and

storage in metal containers. Heat does not reduce

the toxicity of these metals substantially.

Cadmium

0023Cadmium is naturally present at a very low level in

the environment, but large concentrations are pro-

duced as waste byproducts of electroplating, rust

proofing, color tints for paint, plastic stabilizers,

and batteries. Effluents also arise from textile, porcel-

ain, and enamel manufacturing. Crops grown in

sludge containing cadmium can accumulate the metal

up to 13 times the soil concentration. When cadmium

salts are released into an aquatic environment, crust-

aceans and fish accumulate quantities large enough to

be hazardous if they are a part of the regular diet. (See

Cadmium: Toxicology.)

Lead

0024Lead present in rocks and soil may be accumulated in

plants and transmitted to humans through the food

chain. However, most lead comes from atmospheric

aerosols and dust particles through industrial pro-

cesses and automobile emissions, although lead is

less used as a petroleum additive today. Urban

areas therefore contain more lead particles than

rural regions. These fall on soil and are absorbed by

crops. Modern canning uses lacquer, side-seam welds,

and seamless two-piece cans to replace lead solders.

Acidic foods or beverages stored in ceramic vessels

made with glazed lead salts or galvanized pans have

accumulated lead. In addition, the alimentary tract

can receive lead from potable water transported

by lead piping or stored in lead-lined tanks, and

through the compulsive nibbling by children of

paint chips containing lead, with up to 550 mg per

day being accumulated. Lead is a cumulative poison,

and chronic exposure may lead to damage to the

brain, liver, peripheral and central nervous system,

and reproductive, renal, and immune systems. (See

Lead: Toxicology.)

CONTAMINATION OF FOOD 1597

Arsenic

0025 Arsenic is widely distributed throughout the earth and

reaches food sources from water through the dissol-

ution of minerals and ores, from industrial effluents,

and from atmospheric deposition; concentrations in

ground water in some areas are sometimes elevated as

a result of erosion from natural sources. The average

daily intake of inorganic arsenic in water is estimated

to be similar to that from food. Arsenic is used com-

mercially in the production of pharmaceuticals,

metals, herbicides, wood preservatives, and sheep

dips. Arsenic compounds have occurred in seafood,

eggs, and cheese. Chronic poisoning from arsenic is

unusual unless it occurs naturally in the water supply.

However, inorganic arsenic is a documented human

carcinogen, and a relatively high incidence of skin and

possibly other cancers that increase with dose and age

has been observed in populations ingesting water con-

taining high concentrations of arsenic.

Mercury

0026 Mercury is used in electrodes, the manufacture of

plastics, slimecides in the pulp and paper industry,

paints, and fungicides. In the environment, the toxic

form is methyl mercury, which is a neurotoxin as well

as a teratogen. The mercury content of crops may

increase with the use of sewage sludge. It is found in

fish and shellfish living in water contaminated from

industrial wastes and in large lakes artificially created

for hydroelectric power from drowned, decaying

vegetation. Acid rain also helps to mobilize industrial

aerosols into water supplies. People with a regular

diet of fish containing high levels of organic mercury,

or shellfish containing inorganic mercury, are at

greatest risk. (See Mercury: Toxicology.)

Tin, Copper, and Antimony

0027 Although tin can reach aquatic environments through

natural sources, industrial pollution and antifouling

paint on boat hulls, there is little evidence that it can

cause chronic human illness. However, acid foods

in tin-lined cans are able to dissolve enough metal

to cause acute gastroenteritis. Both copper and an-

timony become toxic when they are in contact

with acidic liquids. Copper pipes used in soft-drink

vending machines, and antimony-lined bowls or cups

have been implicated in acute illness. The speed of

metal solubilization depends on the acidity of the

liquids, temperature and time of exposure.

Fluoride

0028 The beneficial effects of fluoride in drinking water on

teeth have been demonstrated, but fluoride can be

toxic, and intakes of more than 10 mg per day are

not recommended. The total consumption of fluoride

from both water and food prepared using water has

to be considered in determining intake levels.

Lubricants

0029Polychlorinated biphenyls and polychlorinated naph-

thalenes were produced as lubricants and should not

be brought into contact with food or feed, but cattle

may ingest them by licking the oils from farm ma-

chinery or animal feed containing leaked oil. Affected

animals develop a debilitating condition, and human

ingestion of milk is considered hazardous. Because of

their extreme persistence in the environment, PCBs

are not only banned from future use but are being

removed from aging equipment, e.g., transformers,

and are destroyed by incineration. Polybrominated

biphenyls have also been accidently fed to livestock

with resultant human exposure through milk and

meat.

Veterinary Drug Residues

0030Antibiotics are added to reduce disease and improve

the growth of farm animals and aquaculture fish;

these are of less concern for their chemical effect

and more for their ability to increase antimicrobial

resistance in strains that might subsequently infect

humans. There is evidence that antimicrobial resist-

ance is increasing worldwide but particularly in de-

veloping countries. Steroids and growth hormones

are used to increase productivity, e.g., bovine somato-

trophin for milk, synchronize breeding cycles, and act

as tranquillizers. The human effect of consuming

foods with these drugs is still being debated, but

many countries refuse to accept products derived

from animals given these drugs. Also, some drug

residues may be allergenic, e.g., penicillin. The with-

drawal times of such drugs are critical to keep the

residues in food as low as possible.

Undesirable Fermentation Products

0031The carcinogen ethyl carbamate is a natural fermen-

tation product in the production of wine, either

through reaction of ammonia with the antimicrobial

agent diethyl pyrocarbonate or through ethanol with

carbamyl phosphate. Limits of 30 mg per kilogram of

wine and 400 mg per kilogram of brandy have been set

to reduce the level of carbamates for human expos-

ure. There have been over 1500 cases and 20 deaths

owing to eosinophilic myalgia syndrome in the USA

from tryptophan dietary supplements contaminated

with derivatives of l-tryptophan. These contaminants

1598 CONTAMINATION OF FOOD

were thought to have arisen during the fermentation

process when a genetically modified strain of Bacillus

amyloliquefaciens was used to produce the trypto-

phan. However, some purification steps were left out

of the process at the same time, and no satisfactory

explanation for the contamination has been made.

Radionuclides

0032 Radionuclides are normally present in the environ-

ment at low levels from naturally radioactive rock but

can also arise from atmospheric fallout from nuclear

tests and gaseous emissions and spills from accidents

at nuclear reactors. Food is one possible means of

transmitting radionuclides to the human body, with

a danger for long-term carcinogenic, teratogenic, or

mutagenic effects. Higher doses may also affect re-

productive capability and shorten the lifespan.

Radium-226 and uranium-238 are naturally occur-

ring radioactive elements that may be at high levels

in certain locations because of the underlying rock

structure. Cereals are the food items that contribute

the most radium-226 to our diet. Fallout from tests or

accidents persists longer in arctic zones, and persons

eating an exclusive meat diet, such as Lapps and the

Inuit, are at highest risk from lead-210 and polonium-

210. Milk and meat supply most of the radionuclides,

such as strontium-89, strontium-90, iodine-131, and

cesium-137, to our bodies. The direct effects of the

Chernobyl nuclear reactor explosion in Ukraine in

the immediate area of the reactor were extreme, but

worldwide contamination was not as high as was

originally feared and had no lasting impact on the

food supply. (See Radioactivity in Food.)

Packaging and Storage

0033 Packaging can exist in various forms, from crates to

wraps. Wood preservatives, such as phenols or copper

arsenates, and insecticides against termites, used in

crates, can contaminate food during shipping through

direct contact or vapors. Wood shavings used for

packing can also transfer these chemicals to foods,

or to animals if the shavings are used for bedding. In

addition, food stored in rooms with walls covered

with insecticidal paint, or containing pest strips from

which pesticides evaporate over a long period of time,

may become exposed to the chemical.

0034 Paper, cardboard, plastic wrap, or aluminum foil

may not keep out lindane vapors if not properly

wrapped. Phosphoric acid esters as flame retardants

in paper, adhesives, and plastic wrappers, e.g., bread

bags and margarine or butter wraps, can reach food.

Diffusion through these is dependent on the time of

contact and type of food wrapped (lipid-rich or moist

foods absorb better than other foods). Hermetically

sealed containers protect food from all chemical and

microbial contaminants if the process is carried out

correctly.

Tampering Problems

0035For centuries, food has been adulterated for fraudu-

lent purposes or deliberately contaminated for injur-

ing or killing specific persons. Recently, commercially

produced food has been tampered with for a variety

of reasons, including product extortion to obtain

money from a company or life insurance firm, at-

tempts to ruin a company by a dissatisfied customer

or disgruntled employee, attention in the media for a

political cause, or as a joke to observe the reaction of

those affected. In dioxin contamination of feed, there

may be some situations where this is deliberately done

to use waste oils mixed with vegetable oils. Tamper-

resistant and tamper-evident packaging has reduced,

but not eliminated, these problems. Nowadays the

possibility of contamination of the food chain,

water supplies or even retail food is a real threat of

bio terrorism. (See Adulteration of Foods: History

and Occurrence; Detection.)

See also: Adulteration of Foods: History and

Occurrence; Detection; Food Poisoning: Tracing Origins

and Testing; Statistics; Fumigants; Lead: Toxicology;

Mercury: Toxicology; Mycotoxins: Occurrence and

Determination; Nitrosamines; Parasites: Occurrence

and Detection; Illness and Treatment; Pesticides and

Herbicides: Types of Pesticide; Toxicology;

Radioactivity in Food; Viruses

Further Reading

Carranza-Lira S and Bueno Fontal JP (2000) Modification

of corporal weight, body fat distribution, blood lipids

and glucose levels in oral contraceptive users. Medical

Science Monitor 6(5): 941–944.

Eck LH, Bennett AG, Egan BM et al. (1997) Differences in

macronutrient selections in users and nonusers of an oral

contraceptive. American Journal of Clinical Nutrition

65(2): 419–424.

McLean JA, Barr SI and Prior JC (2001) Cognitive dietary

restraint is associated with higher urinary cortisol excre-

tion in healthy premenopausal women. American Jour-

nal of Clinical Nutrition 73(1): 7–12.

Masse PG, Van den Berg H, Livingstone MM, Duguay C and

Beaulieu G (1998) Nutritional and psychological status

of young women after a short-term use of a triphasic

contraceptive steroid preparation. International Journal

for Vitamin & Nutrition Research 68(3): 203–207.

Pelkman CL, Chow M, Heinbach RA and Rolls BJ (2001)

Short-term effects of a progestational contraceptive drug

on food intake, resting energy expenditure, and body

weight in young women. American Journal of Clinical

Nutrition 73(1): 19–26.

CONTROLLED-ATMOSPHERE STORAGE

Contents

Applications for Bulk Storage of Foodstuffs

Effects on Fruit and Vegetables

Applications for Bulk Storage of

Foodstuffs

J Saxena, Banasthali Vidyapith, Rajasthan, India

H Gourama, Pennsylvania State University, Reading,

PA, USA

S L Cuppett and L B Bullerman, University of

Nebraska-Lincoln, Lincoln, NE, USA

Background

0001 Planting and harvesting of fruits and vegetables

are determined by many factors including season of

the year, the cultivars, climatological conditions,

and the type of soil. In addition, since the majority

of fruit and vegetable consumers are often located

far from growing areas, most crops must be stored

then transported to marketplaces if demand for them

is to be satisfied throughout the year and through-

out the world. Because fruits and vegetables are

essential sources of vitamins, minerals, fiber, and

other nutrients, consumers are demanding a larger

and more consistent supply of these products. Con-

trolled atmosphere (CA) storage of fruits and vege-

tables not only increases the shelf-life of these

products and maintains good quality but also allows

for a consistent year-round supply in the marketplace.

CA storage has been shown to lengthen the shelf-life

of fruits and vegetables by controlling their levels

of transpiration, respiration, and diseases.

CONTROLLED-ATMOSPHERE STORAGE/Applications for Bulk Storage of Foodstuffs 1601

Control of Undesirable Plant Processes

0002 The quality of fruits and vegetables after harvest

depends upon whether they were harvested at the

right maturity stage, and if the metabolic activities

after harvest are controlled. Some of the physiological

activities of fruits and vegetables such as respiration

and transpiration continue after harvest. However,

other metabolic activities of these plant products

such as photosynthesis and water absorption through

the roots stop at harvest. All of these changes create

metabolic stresses on fruits and vegetables that

shorten the storage life of these crops and reduce the

nutritional and organoleptic quality. Optimal storage

conditions after harvest can control the loss of quality

of these products by maintaining metabolic homeo-

stasis and by minimizing processes like transpiration,

respiration, sprouting, and elongation of existing

structures, seed germination, and greening.

Control of Transpiration

0003 The loss of moisture after harvest can lead to many

changes in the texture and structure of plant products

such as shriveling, shrinkage, and product loss. Thus,

minimizing the amount of water loss during the post-

harvest period is critical for maintaining good quality

and freshness of these products. Transpiration rates

depend not only on the type of plant product but

also on the humidity and temperature of the external

environment. Reduction of the rate of transpiration in

these food products can be achieved by maintaining

low temperatures, high relative humidities, and small

vapor pressure differences during storage.

Control of Respiration

0004 Respiration in plant products is defined as a physio-

logical process by which plant tissues exchange gases

with the surrounding environment. The principal out-

come of this physiological process is the metabolic

transformation of carbohydrates such as starch and

oxygen to carbon dioxide and water through glycoly-

sis, the Krebs cycle, and the electron transport chain.

Respiration, if allowed to occur to any extent, pro-

duces heat, thus affecting the temperature of the

product. Generally it is known that fruits and vege-

tables with high respiration rates such as broccoli,

sweet corn, mushroom, and asparagus are perishable,

whereas products with low respiration rates are stable

during storage. The respiration rate of fruits and

vegetables is influenced by oxygen level, temperature,

carbon dioxide, ethylene, and physical stress. Control

of temperature by refrigeration is critical in reducing

the rate of respiration. However, many products, such

as melons, peppers, cucumbers, etc., cannot be stored

for a long time under refrigeration because of their

susceptibility to chill injury. Additional control meas-

ures such as appropriate packaging and transporta-

tion, modified atmosphere (MA) storage, and CA

storage of fruits and vegetables should be imple-

mented.

0005Pioneering work has led to the development of CA

storage, an effective process that can extend the shelf-

life of fruits and vegetables by controlling the gases

within the storage environment. CA and MA are

basically processes that change the normal compos-

ition of the air (78% N

, 21% O

, 0.03% CO

)

surrounding fruits and vegetables. CA storage is usu-

ally used in conjunction with refrigeration. The first

studies regarding fruit preservation in a gaseous

medium were carried out in an atmosphere consisting

of more carbon dioxide and less oxygen than is nor-

mally present in the air. The benefits of CA and MA

include slowing down the respiration rate, sensitivity

to ethylene, and, consequently, the ripening process,

inhibition of microbial growth, and control of insects.

The exact gas composition will depend on the type of

product, temperature, and length of treatment. CA

and MA have been proven to be beneficial for vege-

tables such as cauliflower, asparagus, brussels sprouts,

celery, mushrooms, cabbage, lettuce, peppers, broc-

coli, and other vegetables. Among vegetables, arti-

chokes may be held in 2–3% carbon dioxide and

2–3% oxygen, asparagus in 5–10% carbon dioxide

and atmospheric oxygen (air), broccoli in 5–10%

carbon dioxide and 1–2% oxygen, cabbage in

3–6% carbon dioxide and 2–3% oxygen, okra in

3–5% oxygen and 0% carbon dioxide at 8–12



radishes in 1–2% oxygen, 0% carbon dioxide at

0–5



C, mature tomatoes in 0–3% carbon dioxide

and 3–5% oxygen at 12–20



C, and partially ripe

tomatoes in 0–5% carbon dioxide and 3–5% oxygen

at 8–12



C. Generally, the relative humidity for the CA

of vegetables varies from 90 to 98%. CA storage was

also found to reduce chilling injuries to cucumbers.

0006CA storage has also been proven to be good for

maintaining the quality and extending the shelf-life of

fruits. CA storage has been shown to improve the

chilling sensitivity, retarding the ripening and senes-

cence and controlling microbial and insect attacks.

One of the principal commercial fruits with which

CA storage has been used successfully is apples. Gen-

erally, apples are stored in 1–3% oxygen and 1–5%

carbon dioxide at 0–5



C, depending on the variety.

These apples are typically harvested before or at the

beginning of the increase in the respiration rate.

During CA storage, apples can go through many

chemical and physiological disorders, such as devel-

opment of bitter pit, corky lesions, and superficial

1602 CONTROLLED-ATMOSPHERE STORAGE/Applications for Bulk Storage of Foodstuffs

scald. CA storage of Golden Delicious apples at low

temperatures and low oxygen atmospheres produces

the highest amounts of volatile aroma compounds

such as branched-chain esters. Low-oxygen atmos-

pheres have also been found to be beneficial for fruit

firmness, acidity, and color. It has been reported that

there are many advantages in storing apples in CA for

a long period of time (up to 3 years) over normal air

storage. These advantages include maintenance of

firmer fruits, good skin color, higher soluble solids,

and low pH. It has also been found that the develop-

ment of flesh browning after short exposure of ‘Fuji’

apples to 20-kPa carbon dioxide is a good prediction

of CA-induced flesh browning. CA storage has also

been shown to extend the shelf-life of green bananas

by storing them in 2–5% oxygen and 2–5% carbon

dioxide at an optimal temperature of 13



C. It has

been reported that equal amounts of oxygen and

carbon dioxide (5%) at 11.7



C are suitable for

Gros Michel bananas held for 20 days. Lacatan and

Dwarf Cavendish bananas have been effectively

stored for 3 weeks using CA storage conditions of

6–8% carbon dioxide and 2% oxygen at 15–15.5



A mixture of 5–10% oxygen and 0–5% carbon diox-

ide is generally effective for oranges, 5–10% oxygen

and 0–10% carbon dioxide for lemons, 1–2% oxygen

and 3–5% carbon dioxide for peaches, 1–2%

oxygen and 0–5% carbon dioxide for plums and

prunes, 5–10% oxygen, 15–20% carbon dioxide for

strawberries, and 3–5% oxygen and 5–10% carbon

dioxide for mangos. The temperature range for CA

storage of fruits varies from 0 to 5



C, and for tropical

fruits, the temperatures are higher, from 5 to 15



Control of Ripening

0007 Prior to senescence, fruits go through a ripening

stage, which consists of biochemical reactions that

transform fruits into sweet, soft products with good

aromas. The color also changes from green to yellow,

orange, and/or red. Fruits can be divided into categor-

ies, based on their ripening physiology. Some fruits,

such as apples, tomatoes and bananas, are referred to

as climacteric, whereas other fruits, such as oranges,

grapes and pineapples, are nonclimacteric. Kidd and

West were the first to establish the relationship be-

tween decreasing oxygen and raising carbon dioxide

and the onset of climacteric changes in apples and

pears. These two types of fruits are distinguished by

their response to the gas ethylene. Climacteric fruits,

when exposed to ethylene, exhibit a respiration surge/

climax, which is coincident with their ripening,

whereas nonclimacteric fruits do not have a respir-

ation climax and show no ripening changes. Also,

during ripening, climacteric fruits produce and

release ethylene into the atmosphere. Ripening in

climacteric fruits hastens their transition into senes-

cence and, therefore, shortens their storage life. Thus,

control of the level of ethylene in the environment is

very important for extending the storage life of cli-

macteric fruits. (See Ripening of Fruit.)

0008Ethylene production in climacteric fruits has an

important physiological role in seed germination,

leaf abscission, ripening of fruits and vegetables, and

the yellowing of leaves. Methionine is the primary

precursor of ethylene biosynthesis. Methionine in

the presence of ATP transforms into S-adenosyl-

methionine, which then transforms into amino-

ocylpropane carboxylate (ACC) and ethylene. ACC

synthase and ACC oxidase are key regulatory

enzymes involved in the biosynthesis of ethylene.

Ethylene’s biosynthesis and physiological function

depend on the oxygen concentration. Apples stored

at 3% oxygen generate up to three times less ethylene

than the apples stored in the air. Golden Delicious

apples stored at low oxygen and at low temperature

receive the highest sensory score after 5 months of

storage. Maintenance of ethylene concentration of

less than 1 mll

1

in CA storage delays fruit softening

and other ripening changes, including the develop-

ment of disorders, such as superficial scald and bitter

pit in apples, both of which are also markedly influ-

enced by preharvest factors and maturity. It is clear

that the potential for disorder development, which

would be readily manifest in air or refrigerated

storage, can be modified significantly by storage in

conditions that induce significantly reduced ethylene

production rates and/or prevent build-up of ethylene

in the storage atmosphere.

0009High concentrations of carbon dioxide suppress

the production of ethylene. A number of investiga-

tions have shown that treatment of fruits with

elevated levels of carbon dioxide leads to an accumu-

lation of ACC. The inhibition of ethylene formation

may be due to the inactivation of ACC oxidase, the

enzyme that catalyzes the reaction of ACC to ethyl-

ene. However, small concentrations of carbon dioxide

(0.1% or lower) have been found to be stimulatory to

the production of ethylene. Reducing oxygen levels

from 2 to 1%, with 1% carbon dioxide at 1



C, leads

to a decrease in the respiration rate of Red Delicious

apples by one-third. Storing apricots at low concen-

trations of oxygen and high carbon dioxide levels

(12–15%) for 30 days or less improves the quality

of Perfection and Rival apricots.

0010Carbon monoxide has also been used in CA stor-

age. Carbon monoxide is an air pollutant that is

hazardous to humans and can affect vegetables

detrimentally before and after harvest, because of its

ethylene-mimicking capabilities. In a study, carbon

CONTROLLED-ATMOSPHERE STORAGE/Applications for Bulk Storage of Foodstuffs 1603

monoxide added to air, or 2% oxygen, reduced the

respiration rate of head lettuce during storage at

2–5



C. Carbon monoxide can stimulate carbon diox-

ide and ethylene production by climacteric fruits but

has little effect on respiration rates on nonclimacteric

fruits, such as strawberries. However, it has been

reported that a combination of 4% oxygen, 2%

carbon dioxide, and 5% carbon monoxide may be

optimal for delaying maturation and ripening, main-

taining good quality and retarding decay during stor-

age of mature green tomatoes at 12.7



C. It has also

been found that packaging precut vegetables, i.e.,

lettuce, cabbage, celery, broccoli, cauliflower, parsley,

and green onions, in 1.5 mil (a mil is a full unit used

for thickness) polyethylene bags and modifying the

atmosphere within these packages to include 25–50%

oxygen and 3–10% carbon monoxide retard brown

discoloration. Carbon monoxide has also been shown

to prevent browning of mushrooms by inhibiting

polyphenol oxidase activity.

0011 Many investigations have shown that preserving

foods by atmosphere modification has more ad-

vantages than disadvantages, depending on the

commodity, variety, atmospheric composition, and

temperature. The advantages of preserving fruits

and vegetables are as follows:

0012 reduction of low-temperature diseases, such as chill

injury during refrigeration;

0013 control of insect and microbial attacks;

0014 better preservation of organoleptic characteristics

such as taste and aroma;

0015 retardation of ripening; and

0016 the period of preservation is significantly longer

than when fruits and vegetables are stored in an

uncontrolled atmosphere.

Potential problems with these processes, especially

MA storage, include the following: storage under

low levels of oxygen may lead to the development of

off-flavors owing to anaerobic respiration; certain

types of defects, such as brown stains on lettuce and

blackheart in potatoes, can be initiated at low levels

of oxygen; and at high levels of carbon dioxide, the

ripening of some fruits can be irregular.

Control of Microorganisms

0017 Fruits and vegetables contain water and other solutes,

which are utilized by microorganisms deposited on

their surfaces during the growing season. Most of the

microorganisms are opportunistic, invading the tissue

as it matures, particularly if the crops are stored

under conditions of high temperatures and humidity.

Although fungi and bacteria cause substantial losses

in vegetables and soft fruits, most losses are caused by

molds, since the inherent acid conditions of the prod-

uct delay bacterial growth. (See Spoilage: Bacterial

Spoilage; Molds in Spoilage.)

0018It is difficult to determine the full extent of post-

harvest losses caused by microorganisms; however,

conservative estimates place US losses at around

24% of the harvested crops of fruits and vegetables.

Postharvest losses have been estimated to be 50% of

the harvested crop, and much of this is due to rot

caused by microbes, especially fungi. Fruits and vege-

tables are frequently washed with recirculating water

after harvest. This water is often contaminated with

soft-rot bacteria and fungi, because of the recircula-

tion, and these can contaminate fresh commodities.

Therefore, an effective concentration of a broad-

spectrum antimicrobial agent should be maintained

in water used for handling fruits and vegetables in

order to kill potential pathogens and spoilage micro-

organisms. Chlorine and sodium orthophenylphenol

(SOPP) have been used for this purpose. Bananas are

generally surface-contaminated with several fungi,

i.e., Cephalosporium, Gloeosporium, Fusarium, and

Verticillium species, which may cause crown rot

during marketing. These fungi can be killed by expos-

ure for 1 min to 2 ppm chlorine in water.

0019Care must also be taken in properly maintaining

the storage environment of fruits as a means of

controlling microbial losses. Rooms used for ripening

bananas, degreening citrus fruits, and refrigerated

storage can become heavily infested with spores of

pathogenic fungi. These rooms may be disinfected

easily and economically by atomizing a water solu-

tion containing 1% formaldehyde or 5% sodium

hypochlorite into the atmosphere and closing the

room for a few hours. Gaseous nitrogen trichloride

and sulfur dioxide have also been used to disinfect

lemon and grape storage rooms, respectively. Brief

heat treatment has been shown to be most successful

in eradicating latent or incipient fungal infections in

several fruits. Hot water is the best heat-transfer

medium because of the availability, heat capacity,

and lack of residues on the fruits. Hot water has

been advocated for control of Penicillium and Diplo-

dia species on oranges, Colletotrichum species on

papaya and mango, and crown rot of banana.

0020Irradiation has also been investigated as an alterna-

tive to chemical means to control insect and fungal

contaminants. Irradiation has also been shown to

extend the shelf-life of fruits and vegetables by

delaying the ripening process. The use of gamma

irradiation has shown promising results in controlling

specific infections in apples. Ionizing radiation doses

for up to 100 krad has been approved for the treat-

ment of produce. Infection may also be prevented by

the use of fungicides before harvest or before storage.

1604 CONTROLLED-ATMOSPHERE STORAGE/Applications for Bulk Storage of Foodstuffs

Many weak acids, such as benzoic, sorbic, propionic,

acetic, nitrous or sulfuric acid, are used to control

molds in foods and stored products. (See Fungicides.)

0021 Biological control of postharvest diseases is an

emerging area that has has been widely investigated,

owing to increased concern over the safety of these

chemicals and to development of resistance of

number of plant pathogens to these chemicals. A

number of biological controls have been tried, includ-

ing antagonistic microorganisms, induced resistance,

and the use of natural antimicrobial substances.

Trichoderma viride has been applied to strawberry

plants to partially control gray mold caused by Botry-

tis cinerea on strawberry fruits after harvest. Brown

rot on peaches has been controlled by Bacillus sub-

tilis. Many investigators are trying to enhance the

natural defense mechanisms of fruits and vegetables

such as the reinforcement of plant cell wall, phyto-

alexins, PR proteins, and constitutive inhibitors such

as monoterpene aldehyde. Other potential nonchemi-

cal control mechanisms include the use of ultraviolet

light, heat treatment, calcium chloride, and chitosan.

0022 A storage atmosphere that has been modified by

reducing the oxygen level and increasing the carbon

dioxide level can influence the development of post-

harvest diseases either by direct inhibition of the

pathogen or by altering the resistance of the host. It

has been found that 30–40% carbon dioxide in the

storage atmosphere inhibits the development of sev-

eral pathogenic fungi on temperate zone fruits. Trop-

ical fruits may be less tolerant to high levels of carbon

dioxide. The following are recommendations for some

tropical fruits: avocado in 2–5% oxygen and 3–10%

carbon dioxide, banana in 2.5% oxygen and 2.5%

carbon dioxide, mango in 3–5% oxygen and 5–

10% carbon dioxide, papaya in 2–5% oxygen and

5–8% carbon dioxide, and pineapple in 2–5%

oxygen and 5–10% carbon dioxide.

0023 The most commonly used gas combination is 5%

carbon dioxide and 3% oxygen, a mixture that pro-

vides good storage conditions, along with low tem-

peratures (0–4.4



C). Dry ice can be used to increase

the carbon dioxide content to 10–45% during transit

or short-time storage. Such treatment is beneficial for

sweet cherries, strawberries, raspberries, and several

other products. Among vapor treatments, sulfuric

fumigation is a standard practice for control of

decay of grapes in storage, but it is injurious to most

other fruits and vegetables. Biphenyl pads have been

used to control decay in packages of some citrus

fruits. (See Fumigants.)

0024 Another potential disinfectant for fruits and vege-

tables is ozone. This has been extensively investigated

over the last few years. Ozone dissolved in water has

been shown to be effective in sanitizing the surface of

fruits and vegetables. Sodium orthophenylphenate is

frequently used as an antiseptic wash or in a wax on

several crops including citrus fruits, pears, sweet

cherries, and sweet potatoes.

Control of Insect Pests

0025Insect pests, along with microbial diseases and spoil-

age, are responsible for much storage loss that causes

extensive economic losses. Various control methods

are available for these pests, including hygiene and

cultural control, physical control, physical barrier,

and chemical and biological control. Treatment by

hot water or hot air has been used to control insects

and increase the shelf-life of fruits and vegetables.

Postharvest has also been found to affect the senes-

cence of fruits by influencing the rate of respiration

and ethylene synthesis. (See Insect Pests: Insects and

Related Pests; Problems Caused by Insects and Mites.)

Use of Fumigants

0026Typical fumigation procedures expose the fruit, at

ambient or near ambient temperatures, for several

hours to methyl bromide or ethylene dibromide at

concentrations of 45 g to a few kilograms per

1000 m

of air space in air-tight chambers. The fumi-

gants are highly toxic, and their residues can pose an

additional problem in the use of chemical fumigants.

For the safety of operators and consumers, applica-

tions of fumigants should follow the standards set by

the proper regulatory agencies.

Use of Gas Control

0027Strict control of storage atmospheres has many

advantages such as delay of maturation, ripening,

senescence, insects, and microorganisms. Treatment

of European red mite on Delicious and Spartan apples

with close to 100% carbon dioxide or nitrogen at 21–



C provides a 100% kill in 2 days. A mixture of

60% carbon dioxide with air provides no mite mor-

tality, even after 7 days of exposure. This indicates

that the biocidal effect resulted from low oxygen. The

effects of carbon dioxide are also more or less the

same on a number of other insects of economic im-

portance. The codling moth is also sensitive to high

carbon dioxide and low oxygen levels. The possible

phytotoxicity caused by such an atmosphere indicates

a potential for using high levels of carbon dioxide on

some apple cultivars. Laboratory tests have shown

the effects of high carbon dioxide (60%) and low-

oxygen (0.5%) atmospheres, applied at 25



C and at

relative humidities of 60 and 95%, as reducing the

amount of time required for codling moth mortality.

CONTROLLED-ATMOSPHERE STORAGE/Applications for Bulk Storage of Foodstuffs 1605