Yam, Kit L. (ed.). The Wiley encyclopedia of packaging technology

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application of the common atmospheric gases and the

beneﬁcial effects conferred by speciﬁc concentrations of

various gases. Thus, the technologies, rely on gases that

are safe, common, cheap, readily available, and usually

not considered chemical additives. Different combinations

of these gases are appropriate for different foods, package

types, and situations. The proper marriage of food, gas

mixture, and package type has been the subject of most of

the developmental efforts in the area.

Vacuum packaging (VP) is a form of MAP that estab-

lishes an atmosphere by drawing a partial vacuum to

remove the ambient gases inside a gas barrier package

and then sealing the package with the purpose of exclud-

ing atmospheric gases, principally O

. A complete vacuum

is never established under practical conditions but the

exclusion of gases is the aim.

MAP/VP are employed to delay deterioration of foods

that are not sterile and whose enzymatic systems may still

be operative. Thus, these techniques differ from tradi-

tional methods of food preservation, such as cooking,

canning, drying, salting, or freezing, but rather are meth-

ods to maintain foods in a ‘‘natural’’ condition while

slowing speciﬁc deterioration processes. Rigorous tem-

perature control is often necessary for the packages to

work properly. For this reason, the capabilities of the

distribution system or ‘‘cold chain management’’ deﬁne

the degree to which MAP can be used. These packaging

technologies have ﬁt very well into the vertically inte-

grated, geographically restricted distribution systems in

Western Europe. Although they have been more difﬁcult

to implement in the more fragmented and longer distance

distribution systems of North America, they are now used

commonly in all types of food packaging.

GASES USED IN MAP

Oxygen (O

)

Most of the reactions with food constituents involving

oxygen are degradation reactions resulting in the oxida-

tive breakdown of foods into their constitutive parts.

Oxygen combines readily with fats and oils and causes

rancidity. In addition, most spoilage microorganisms re-

quire O

to grow and will cause off odors in the presence

of sufﬁcient oxygen. Oxygen is necessary to the normal

respiratory metabolism of fresh fruits and vegetables, and

normal atmospheric concentrations of O

contribute to

senescence and degradation of produce quality. Oxygen is

implicated in staling of bakery goods and pasta. It oxidizes

the pigments of red meats to an undesirable brown color.

In the absence of O

, meats will take on a purplish color

that some consumers ﬁnd objectionable.

Oxygen permeates through plastic polymers at rates

depending on the polymer, but it generally permeates

more slowly than carbon dioxide. The permeability rate

of oxygen (and all gases) in plastics increases as tempera-

ture increases. Similarly, the chemical reactivity of oxygen

with food constituents increases as temperature increases.

Carbon Dioxide (CO

)

Carbon dioxide is present in the atmosphere at low

levels (B0.03%) but is a product of combustion and so is

easily produced. It is very soluble in water, especially in

cold water (179.7 cm

/100 mL at 01C), and will thus be

readily absorbed by high-moisture, refrigerated foods.

Carbon dioxide is soluble in fats and oils, as well as

in water, and this solubility can lead to package collapse,

off ﬂavors, excess purge by muscle foods, and discolora-

tion of fresh produce. Carbon dioxide permeates most

packaging materials more rapidly than other atmospheric

gases.

When CO

dissolves in water, it has an acidifying effect.

This acidiﬁcation, as well as direct antimicrobial effects of

W10–15%, can suppress the growth of many spoilage

microorganisms and for this reason it is an important

component of MAP.

Carbon dioxide also suppresses the respiration of some

fresh fruits and vegetables and thus can help extend their

shelf lives. In addition, CO

, concentrations above about

1% can render many plant tissues insensitive to the

ripening hormone ethylene and thus slow their senescence

and deterioration. However, too much CO

can be dama-

ging to plant tissues and individual fruits and vegetables

differ in their tolerance of CO

Nitrogen (N

)

Nitrogen is the most abundant component in air (B78%)

and can be used in either gaseous or liquid form. It is

physiologically inert in its gaseous and liquid forms and is

used in packaging primarily as a ﬁller and to exclude

other more reactive gases. It is sparingly soluble in water

(2.33 cm

/100 mL at 01C).

Carbon Monoxide (CO)

Carbon monoxide is a colorless, odorless, tasteless, very

toxic gas that is effective as a browning and microbial

inhibitor. In concentrations as low as 1%, CO will inhibit

the growth of many bacteria, yeasts, and molds. It can also

delay oxidative browning of fruits and vegetables when

combined with low O

concentrations (2–5%) and has

found limited use commercially for this purpose. By add-

ing minute amounts of CO to red meat packages, products

such as ground beef can maintain their natural appear-

ance throughout their shelf life, since CO reacts with the

meat pigment myoglobin to create carboxymyoglobin, a

bright red pigment that masks the natural aging and

spoilage of meats. However, the beneﬁts and risks of using

CO in MAP remain controversial, and due to the toxicity of

the gas and its explosive nature at 12.5–74.2% in air, it

must be handled using special precautions.

Sulfur Dioxide (SO

)

Sulfur dioxide has been used to control growth of mold and

bacteria on a number of soft fruits, particularly grapes and

dried fruits. It has also found use in the control of

788 MODIFIED ATMOSPHERE PACKAGING

microbial growth in fruit juices, wines, shrimp, pickles,

and some sausages. Sulfur dioxide is very chemically

reactive in aqueous solution and forms sulﬁte compounds,

which are inhibitory to bacteria in acid conditions (pH

o4). However, a signiﬁcant minority of people display

hypersensitivity to sulﬁte compounds in foods and the use

of sulﬁtes has come under public and regulatory scrutiny

in recent years.

Ethanol (EtOH)

Ethanol has antifungal activity and has been used with

some baked goods in Japan to reduce microbial spoilage.

In addition, research results have shown ethanol to

enhance ﬁrmness of tomatoes and may act as a ﬂavor

enhancer for other fruits.

Argon (Ar)

Argon, a noble gas, is not known to have any chemical or

biological activity. Nevertheless, reports from one com-

pany suggest that it may have antimicrobial effects. Argon

comprises 0.9% of the atmosphere and so is relatively

abundant.

PACKAGING MATERIALS

Most MAPs rely on ﬂexible monolayer, multiplayer, and

multilayer laminate ﬁlms and/or composite trays to main-

tain product and atmosphere integrity. Polymer-paper and

polymer-foil laminations, as well as metal cans and glass

jars, are also used in such packaging. Many types of

polymers and composite materials are available for these

uses, and more are appearing every day. Polymers prob-

ably comprise upwards of 90% of the materials used in

MAP, with paper, paperboard, aluminum foil, metal, and

glass accounting for the remainder. However, for each

product category, relatively few kinds of materials are

used. The selection of materials depends on technical

considerations of performance, strength, sealability, print-

ability, and recyclability as well as aesthetic, safety, and

cost considerations.

The most commonly used polymers are polyethylene

(PE), polypropylene (PP), polyester, polycarbonate, poly-

styrene (PS), nylon, ethylene–vinyl alcohol (EVOH), poly-

vinylidene chloride (PVDC), ethylene vinyl acetate (EVA),

cellophane, rubber, and butadiene. In addition, sealant

layers of ionomer or other polymer materials are some-

times used.

Barrier Properties

The function of many MAP systems is to exclude O

and

moisture from the packaged food and thereby retard

oxidative rancidity (baked goods, Sous Vide, nuts, and

pasta), retard growth of spoilage microorganisms (meats,

pasta, baked goods), maintain crispness (baked goods and

snack foods), and maintain proper color (red meat). In

other packages, the aim is to prevent egress of CO

retard growth of microorganisms (meat, baked goods and

pasta). These packages require the use of gas barrier

materials that allow very litle permeation of gases.

MAP for fresh produce, on the other hand, must allow

entry of a controlled amount of atmospheric O

to main-

tain the aerobic metabolism of the product. In addition,

controlled amounts of CO

must also exit the package to

avoid buildup of injurious levels of the gas. These

packages rely on the use of polymer ﬁlms with either

relatively high gas permeability characteristics or micro-

perforations.

The barrier of a polymeric ﬁlm to a gas is inversely

proportional to the permeability of the ﬁlm (i.e., the higher

barrier, the lower permeability). Gas permeation involves

three sequential steps: adsoprtion of the gas molecules

onto one side of the ﬁlm, diffusion of the gas molecules

across the ﬁlm, and desorption of the gas molecules from

the other side of the ﬁlm (1). The ﬁrst and third step,

adsorption and desorption, may be described as Henry’s

Law:

¼ Sp

where c

is gas concentration at the ﬁlm surface (moles/cc),

p (atm) is partial pressure of the gas, and S is solubility

coefﬁcient (moles/cc/atm). The second step, diffusion, may

be described the Fick’s First Law:

J ¼D

where J (moles/cm

/s) is diffusion ﬂux, D (cm

/s) is diffu-

sivity or diffusion coefﬁcient, c (moles/cc) is gas concentra-

tion, and x (cm) is distance in the ﬂow direction.

Sometimes, small holes or microperforations are incor-

porated in the ﬁlm structure, which have the effects of

increasing the values of permeabilities and decreasing the

permeability ratio of CO

to O

When calculating the permeability of a multilayer

polymer laminate, the following equations may be em-

ployed (1, 2):

þ

where P is the permeability, L is the ﬁlm thickness, the

subscript T refers to the total ﬁlm, and the subscripts 1, 2,

3 refer to the individual layers in the ﬁlm.

Gas barrier properties of plastic ﬁlms are sensitive to

temperature and, in a few cases such as for EVOH or

nylon, relative humidity. As most ﬁlm permeability testing

occurs at room temperature and low relative humidity, it

is often difﬁcult to predict barrier performance under the

high humidity refrigerated conditions typical of extended

shelf life fresh foods. As a rule, both WVTR and gas

transmission rates increase with increasing temperature

(see also Barrier Polymers).

MODIFIED ATMOSPHERE PACKAGING 789

ACTIVE PACKAGING

Besides gas ﬂushing, gas injection, and wrapping in

packages that mediate or obstruct gas movement, there

are a growing number of supplementary materials that

can be added to MAPs or used with those packages to

further alter and control the package environment. These

include absorbers, emitters, scavengers, scrubbers, and

desiccants that, when added to a package, alter the

package structure, function, or properties. Their purpose

is to extend product shelf life, usually through the control

of atmospheric gases and moisture, without the use of

‘‘preservatives.’’ These materials are diverse and their

claims in the marketplace may sometimes outpace their

capabilities. But there is no question that this is a rapidly

growing area of packaging that is likely to move into the

mainstream of food packaging in the near future (3).

Oxygen Absorbers

For packaging applications that involve oxygen-sensitive

products, gas ﬂushing with nitrogen or carbon dioxide

often is insufﬁcient to remove residual oxygen. Because

low concentrations of oxygen can participate in the de-

gradation of fatty foods, accelerate staling of baked goods,

and facilitate other forms of deterioration, the use of

oxygen absorbers as an adjunct to gas ﬂushing has become

an important methodology. Most commercially available

absorbers use metallic reducing agents such as pow-

dered iron oxide, ferrous carbonate, or metallic platinum.

Iron powder is the most common active ingredient. These

products often utilize powdered FeO, which becomes

and Fe

and their hydroxide forms after absorp-

tion of O

. The lower the temperature, the lower the O

absorption speed (4, 5).

Reduced iron is listed as GRAS (generally regarded as

safe by the FDA) with no limitations on its use other than

good manufacturing practices. It should be pointed out

that the use of O

scavengers reduces O

to levels that

may be conducive to the growth and toxigenesis of certain

anaerobic pathogens, notably Clostridium botulinum, and

thus should be used with great care with nonsterile fresh

foods.

Carbon Dioxide Absorbers

Some of the absorbents that are currently being used to

remove excess CO

from CA storage rooms could be adapted

for their utilization in MAP. They include lime (calcium

hydroxide [Ca(OH)

] + sodium hydroxide or potassium hy-

droxide), activated charcoal, and magnesium oxide (5).

Moisture Regulators

The stability and shelf life of many food products depends,

in part, on the maintenance of an appropriate water

activity inside the package. Inappropriate moisture levels

can lead to shortened shelf life, reduced quality, and, in

the worst case, unwanted microbiological activity. While

many ﬁlms are available that will provide an excellent

moisture barrier to prevent the ingress or egress of

unwanted moisture, often the food product itself can

contribute unwanted humidity within a package. Several

products are available that will aid in the regulation of

proper moisture within the package. Most rely on physical

absorption of moisture, though a few rely on actual

chemical bonding to the water molecules. The most com-

mon desiccants currently used are based on silica gel,

montmorillonite clay, calcium oxide, activated carbon, or

glycerol. Of these, silica gel is the most common.

Silica gel is a partially dehydrated colloid of silicic

acid. Its structure is such that it forms interconnected

micropores that form a vast surface area that can

attract and hold water through adsorption and capillary

condensation. Silica gel is most efﬁcient at temperatures

below 251C where it can adsorb up to 40% of its weight in

water. Its efﬁciency falls off at higher temperatures. Silica

gel is nontoxic and noncorrosive. Montmorillonite clay is

less efﬁcient at moisture adsorption than silica gel and

also slower.

Alternatively, saturated salt solutions can be employed

to maintain a desired equilibrium relative humidity

within the package. Individual salts, if present in sufﬁ-

cient quantities, will maintain a characteristic relative

humidity (RH) at a given temperature. For example, NaCl,

at 5 1C, will maintain a RH of 75%. For a higher equili-

brium RH, K

,at51C, will maintain an RH of 98.5%

(6, 7). Selection of the proper salt can result in almost any

desired RH.

Absorbers/emitters of Ethylene and Other Volatiles

Because ethylene gas is a plant hormone with powerful

physiological effects at very low concentrations, it is

sometimes removed from the environment of sensitive

commodities. Ethylene gas (C

), in part per million

concentrations, can induce rapid ripening and senescence

in many fruits, yellowing of leafy vegetables, and physio-

logical injury of selected produce items. Potassium per-

manganate has long been used to remove ethylene from

controlled atmosphere apple storage rooms. The same

compound, adsorbed on various inert substrates, is avail-

able commercially in sachets, on pads, or in granular form.

Many other compounds have ethylene adsorbing capacity,

including various hydrocarbons, silicones, glycols, and clay

materials (8).

In addition, many other volatile compounds can be

responsible for off-odors in foods but can be reduced

through the use of absorbers. Potassium permanganate

and activated charcoal are the most important and can

absorb many volatile gases other than ethylene.

Active Films

While the above methods of active package modiﬁca-

tion have their virtues, they all suffer because they

have to be utilized in addition to the packaging itself.

As such, they represent an added expense and, in some

cases, the addition of a potentially hazardous material.

A number of innovative approaches to avoiding these

problems have emerged in the past few years. There are

now several plastic ﬁlms that incorporate some of the

functions described above into the ﬁlm itself. Thus, the

790 MODIFIED ATMOSPHERE PACKAGING

package itself may absorb O

, ethylene or CO

, or control

decay (3).

There are several new ﬁlms, mostly from Japan, that

are reputed to have ethylene-adsorbing capabilities to

improve the shelf life and freshness of fruits and vegeta-

bles. These ﬁlms are typically made of common plastic

polymers (usually low-density polyethylene) with one or

several clay materials (zeolites, cristobilites, etc.) em-

bedded in the ﬁlm matrix. These ceramic materials have

putative ethylene-adsorbing capacity. However, investiga-

tors have found little ethylene adsorbing capacity by

porous ceramic materials (8, 9). Urushizaki (10) tested

one such ceramic material and detected adsorption of less

than 1 mL/g of ceramic material after exposure to 500 ppm

of ethylene. Such adsorptive capacity is insufﬁcient to

be of beneﬁt in a modiﬁed atmosphere package of fresh

produce.

Some ﬁlms containing ceramic materials are claimed to

aid in the preservation of produce through the emission of

farinfrared radiation. Such radiation normally is effective

mainly in heating an absorbing body, in this case the fresh

produce. This is antithetical to the usual aim in preserving

produce. The reputed beneﬁcial effect is that the infrared

radiation excites the plant cell membranes, thereby ren-

dering the cells more resistant to microbial invasion.

Such claims are as yet unsubstantiated in the scientiﬁc

literature.

Films that will pass ultraviolet radiation have been

suggested for reduction of ethylene and for control of

microorganisms. Ultraviolet radiation reacts with oxygen

to form ozone which scavenges ethylene and also kills

microorganisms. Unfortunately, ozone is also very dama-

ging to most plant tissues. In addition, the reaction may

not be very efﬁcient in low oxygen environments such as

those found inside MAP.

A promising approach to reduction of oxygen content

inside a package is based on imbedding in the plastic ﬁlm

a photo-sensitizing dye and an electron-rich oxidizable

compound termed a singlet oxygen acceptor. When irra-

diated with ultraviolet, visible, or near-infrared radiation

of appropriate wavelengths, the excited dye molecules

sensitize oxygen molecules by converting them to the

singlet state. Such oxygen molecules then more readily

react with oxygen acceptor molecules that are also em-

bedded in the ﬁlm (11).

Other workers are making progress in incorporating

antimicrobial agents into plastic ﬁlms so that the package

itself controls bacteria and fungi. Technical hurdles sur-

rounding a percentage of products in contact with the

packaging material exist. In addition , the incorporation of

pesticides in ﬁlms may meet resistance in the current

regulatory climate.

Temperature Switch

Temperture switch polymers, which are relatively new

technologies, are unique polymers that respond to tem-

perature changes in a controllableand very predictable

way. Temperature switch polymers can signiﬁcantly

change their permeability, adhesion, viscosity, or volume

when heated or cooled by just a few degrees above or below

a preset temperature switch (12). Temperature switch

polymers can be very advantageous in packaging applica-

tions when signiﬁcant temperature variations occur

within the distribution channel.

MAP OF RED MEAT

Deterioration of Fresh Meat

Fresh meat undergoes both oxidative color deterioration

and microbiological deterioration. The color of red meat is

determined by the oxidation state of the pigment myoglo-

bin. The reduced form, deoxymyoglobin, is a purple color.

Oxygenated oxymyoglobin is a bright red color associated

with freshness in the minds of many consumers. Atmo-

spheric O

slowly converts myoglobin to the dull brown

metmyoglobin that many consumers associate with

poor quality. Deoxymyoglobin is more susceptible to oxida-

tion than oxymyoglobin, so metmyoglobin forms more

readily at low O

concentrations than at higher concen-

trations (13).

Fresh meat is contaminated on the surface with spoi-

lage bacteria from the slaughtering process. The presence

of O

encourages the growth of aerobic spoilage bacteria,

particularly species of Pseudomonas, which will produce

putrid, malodorous compounds.

Vacuum Packaging

The exclusion of atmospheric O

prevents the oxidation of

myoglobin to metmyoglobin as well as suppressing the

growth of malodorous Pseudomonas bacteria. The delay of

these two primary forms of deterioration through packa-

ging can signiﬁcantly extend shelf life of fresh red meat.

Vacuum packaging has been applied to 2–9 kg primal

and subprimal cuts of meat for distribution to stores.

Appropriate ﬁlms for such packaging must have good

gas barrier properties, generally admitting o50 cc O

24 h/atm (13). In addition, they must resist puncturing by

protruding bone and must be ﬂexible enough to form a

tight ‘‘skin’’ over the meat and prevent pockets of air from

forming where aerobic deterioration could rapidly occur.

Films made of polyamide–polyethylene laminates and

EVA copolymer–PVC/PVDC copolymer laminates, as well

as ionomer–polyamide–EVA copolymer, among others,

have been used for this purpose (17).

When vacuum-packaged meats reach the store, they

are unpacked, cut into appropriate consumer units, and

placed in polystyrene foam trays of PVC trays and

overwrapped with O

permeable ﬁlms. The ingress of

causes the deoxymyoglobin to ‘‘bloom’’ into red

oxymyoglobin.

Vacuum packages for meat are formed in four basic

ways: (i) through heat-shrinking a ﬂexible bag around the

primal cuts, (ii) Using a preformed plastic bag in an

evacuation chamber, (iii) Thermoforming trays in-line

from a base web, or (iv) Vacuum skin packaging in which

the product acts as the forming mold. Vacuum-packaged

beef of normal pH and kept at chill temperature can be

stored for 10–12 weeks. Lamb, because it tends to have

MODIFIED ATMOSPHERE PACKAGING 791

more neutral pH exterior adipose tissue than beef, will

keep 6–8 weeks in vacuum packages (14).

Case Ready Meats

A further evolution of vacumm-packaged meats are case-

ready meats. Case-ready meats are packaged at plants

and delivered to retailers ready to be placed in the retail

case. Case-ready meats employ a combination of MAP

technologies including vacuum packaging as well as low

and high O

MAP (15). Examples of growing case-ready

meats include poultry, beef, veal, pork, and ground meat

products.

High O

MAP

High O

MAP employs 40–80% O

to extend color stability

as well as 20–30% CO

to delay microbial spoilage. How-

ever, the presence of O

can lead to off odors and rancidity

and so high O

MAP has not been suitable for prolonged

storage of red meat.

Low O

MAP

Combinations of low O

and high CO

have been achieved

through gas-ﬂushing packages with N

and CO

The absence O

retards formation of brown metmyo-

globin and the CO

suppresses growth of spoilage bac-

teria. However, because CO

is very soluble in both water

and fat, excess CO

must be added to the package to

allow for the solubility. Package collapse can result unless

in the headspace of the package signiﬁcantly exceeds

the amount of CO

that solubilizes. Such packages

have resulted in shelf lives of 3–4 months for pork and

lamb.

MAP OF POULTRY

Poultry is usually contaminated with a large bacterial

population that consists primarily of spoilage bacteria.

Poultry is high pH compared to red meat and so provides a

good environment for growth of these bacteria. Vacuum

packages are difﬁcult to form around poultry because of

the irregular shape and sharp edges commonly encoun-

tered. Consequently, shelf life in vacuum packages is

usually short, limited to about 2 weeks before putrid odors

develop.

Low O

combined with high CO

has been extensively

used with bulk packaged poultry. Oxygen is removed by

drawing a vacuum and CO

and N

are introduced.

Despite the presence of some residual O

, shelf lives of

2–3 weeks can be achieved (13). Case-ready MAP is also

expanding in poultry, including chicken, turkey, and duck.

MAP OF FRESH FISH

Fish encompasses a great diversity of species and habi-

tats. In general, ﬁsh differ from terrestrial foods in that

the interior of their muscles are not sterile, they undergo

rapid enzymatic breakdown of their proteins even in low

environments, and they are often not raised in

controlled environments. Fish are only as clean as the

water they were taken from. Thus, ﬁsh can be carriers or

several pathogens such as Clostridium botulinum non-

proteolytic types E and B, Vibrio parahaemolyticus, Lis-

teria monocytogenes, and others (16).

Fish rapidly spoil due to the activity of gram-negative

spoilage bacteria and they undergo enzymatic breakdown.

Vacuum and MAP employing high CO

have been used to

extend the normally limited shelf lives of various kinds of

ﬁsh. Gas mixtures of 30% O

, 40% CO

and 30% N

have

been used for nonfatty ﬁsh, while 40% CO

and 60% N

have been used for smoked and fatty ﬁsh, (17).

The use of MAP and vacuum packaging are not capable

of preventing growth and toxin production by C. botulinum

(18). Maintaining the temperature below 31C throughout

distribution is the only barrier to the growth of this

pathogen. While commercially packaged raw ﬁsh have

not been implicated in food poisoning incidents, MAP of

fresh ﬁsh should only be undertaken with extreme caution.

MAP OF BAKERY AND PASTA PRODUCTS

Pasta and baked goods are subject to moisture loss,

oxidative rancidity, and microbiological breakdown, pri-

marily due to growth of molds. MAP has been used

extensively in Europe and, less so, in the United States

to prevent deterioration and extend shelf life. Vacuum

packaging has been used for some baked goods to remove

headspace O

and inhibit oxidative rancidity and growth

of aerobic spoilage microbes. Packaging in a combination

of N

and CO

has been used more commonly to replace O

and suppress growth of bacteria and molds due to the

presence of the CO

. Oxygen absorbers, CO

generators,

and ethanol emitters have been used to extend the shelf

life of baked goods in Japan and other parts of Asia (19).

Because the exclusion of O

is so crucial to MAP of

pasta and baked goods, packaging materials must provide

a good barrier to O

. Rigid trays with nylon/LDPE or PVC/

PVDC lidstocks have been used. Alternatively, laminated

ﬁlms made from nylon/polyethylene, nylon/PVDC/PE, or

nylon/EVOH/PE have also been used. All maintain a

reasonable moisture vapor as well as an O

barrier.

Baked goods have been packaged in atmospheres of 50–

100% CO

plus 0–50% N

, which can result in shelf lives

up to several months for some products. Fresh pasta will

stay fresh in MAP up to 2 weeks if not pasteurized or, in

some cases, 3 months if pasteurized (20).

MAP OF PREPARED FOODS

Chilled, prepared foods are perhaps the fastest growing

area of all food categories, and many of these foods are

being shipped and marketed in MAP. As with all MAP

applications, use of top-quality ingredients, strict adher-

ence to temperature control, and careful sanitation are

prerequisites to entering this market. The most rapidly

growing areas of this sector include such prepared foods

as pasta, pizza, precooked meats, sandwiches, precooked

French fries, and complete prepared dishes such as ‘‘Sous

Vide.’’

792 MODIFIED ATMOSPHERE PACKAGING

Most chilled, prepared foods are packaged in combina-

tions of N

and CO

with little or no O

in the package.

Such atmospheres confer several beneﬁts including reduc-

tions of oxidative rancidity, lack of growth of aerobic

spoilage microorganisms, suppression of growth of molds

by CO

, little moisture loss through the ﬁlm package, and

reduced oxidative breakdown of ﬂavor and aroma

volatiles.

The packages for these products are generally high-

barrier polymer coextrusions or laminations. Packaging

formats can include bags, top- and bottom-forming and

nonforming webs, stand-up pouches, or multilayer lidding

materials sealed onto rigid trays. Most packaging is run

on form/ﬁll/seal machines using with either PVC or EVOH

polymers to provide the barrier properties.

Sous Vide involves vacuum packaging of foods, usually

in multilayer polymer pouches, cooking the vacuum pack-

aged product in a water bath, moist steam or pressure

cooker, cooling rapidly in cold water, and then storing

under refrigeration. These products will have a shelf life

of 2–3 weeks under refrigeration. Cooking under vacuum

protects the ﬂavors from oxidative breakdown as well

as preventing the growth of aerobic spoilage microorgan-

isms (21).

While the food is not sterile, it will have low microbe

counts and refrigeration should prevent growth of those

few microbes that survived the cooking process. Because

the cooking process will not kill spore-forming bacterial

pathogens, the inclusion of barriers to pathogen growth,

such as low pH, reduced water activity, or the introduction

of lactic acid bacteria, in addition to refrigeration, has

been suggested. Sous Vide was developed in France and

has found widespread acceptance there. Acceptance has

been slower in the United States but continues to grow,

particularly in the food service sector.

MAP OF FRESH FRUITS AND VEGETABLES

The primary effects of MAP of fruits and vegetables

are based on the often observed slowing of plant respira-

tion in low O

environments. Reduced respiration leads

to reduced depletion of carbohydrate reserves, slower

ripening of fruits, and longer shelf life. This suppres-

sion of respiration continues until O

reaches about

2–4% for most produce. If O

gets lower than 2–4%

(depending on product and temperature), then fermenta-

tive metabolism can replace normal aerobic metabolism

and off ﬂavors, off odors, and undesirable volatiles can be

produced. Low O

can also reduce enzymatic browning of

injured plant tissues. As CO

increases above the 0.03%

found in air, a suppression of respiration results for some

commodities. Reduced O

and elevated CO

together can

reduce respiration more than either alone. In addition,

elevated CO

suppresses plant tissue sensitivity to the

effects of the ripening hormone ethylene. For those pro-

ducts that tolerate high concentrations of CO

, suppres-

sion of the growth of many bacteria and fungi results at

W10% CO

(22).

Although package O

permeability increases somewhat

as temperature increases, product respiration (demand for

) increases much faster. Thus, O

will rapidly be

depleted if package temperature increases. Because pack-

age performance can only be speciﬁed within a particular

temperature range, it is important that packages be used

within that range. If the temperature gets outside of that

range, product quality will suffer (7).

The rapid growth of the fresh-cut produce industry,

including retail salads, vegetables, and fruits as well as

many fruits and vegetables produced for food service, has

been possible largely due to the improved quality and shelf

life of cut produce in MAP. Products are packaged in a

wide variety of modiﬁed atmosphere packaging including

laminated and/or coextruded copolymers of polyoleﬁns

such as LDPE, EVA, PS, and PP. Packaging formats

include bags, stand-up pouches, lidded trays, and micro-

waveable trays. The choice of the correct polymer or

combination of polymers is often determined by matching

the strengths of particular polymers with the require-

ments of the packaging system, while at the same time

minimizing or masking particular polymer disadvantages

(2). Package atmospheres can be created passively by

sealing the bag and allowing the product respiration to

decrease the O

concentration and increase the CO

concentration until equilibrium is reached. Alternatively,

the atmosphere can be initially rapidly modiﬁed by redu-

cing the package headspace by drawing a vacuum and,

sometimes, by injecting a desirable gas mixture into the

bag. In any case, the equilibrium package atmosphere is

determined by the respiration rate of the product or

product blend, the ﬁnal target modiﬁed atmosphere, and

the gas permeability properties of the package, not by the

initial atmosphere in the bag. Once all of the parameters

have been deﬁned, mathematical models can be used to

determine appropriate ﬁlm breathability characteristics

that will deliver a beneﬁcial atmosphere at the anticipated

processing, storage, and distribution temperatures.

An effective mathematical model to estimate appro-

priate ﬁlm breathablity for a desired atmosphere is as

follows (23):

ðO

2;air

 O

2; pkg

ðCO

2; pkg

 CO

2; air

where

¼ respiration rate (O

consumption rate of

product)

¼ respiration rate (CO

evolution rate of

product)

W = product weight

L = ﬁlm thickness

A= ﬁlm surface area

¼ permeability to O

¼ permeability to CO

2, pkg

= desired O

concentration in package

2, air

concentration in air (typically 21%)

2, pkg

= desired CO

concentration in package

2, air

=CO

concentration in air (typically 0.03%)

MODIFIED ATMOSPHERE PACKAGING 793

BIBLIOGRAPHY

1. D. S. Lee, K. L. Yam, and L. Piergiovanni, Food Packaging

and Technology, CRC Press, New York, 2008, Chapter 4.

2. J. R. Gorny and J. Brandenburg, Packaging Design for Fresh-

Cut Produce IFPA, 2003.

3. M. L. Rooney, ‘‘Active Packaging in Polymer Films’’ in M. L.

Rooney, ed., Active Food Packaging, Blackie Academic &

Professional, 1995, pp. 74–110.

4. J. P. Smith, J. Hosohino, and Y. Abe, ‘‘Interactive Packaging

Involving Sachet Technology’’ in Ref. 1, pp. 143–173.

5. J. P. Smith, Y. Abe, and J. Hoshino, ‘‘Modiﬁed Atmosphere

Packaging—Present and Future Uses of Gas Absorbents

and Generators’’ in J. M. Farber and K. L. Dodds, eds.,

Principles of Modiﬁed-Atmosphere and Sous Vide Product

Packaging, Technomic Publishing Co., Lancaster, PA, 1995,

pp. 287–323.

6. P. W. Winston and D. H. Bates, ‘‘Saturated Solutions for the

Control of Humidity in Biological Research,’’ Ecology 41(1),

232–237 (1960).

7. D. Zagory, ‘‘Principles and Practice of Modiﬁed and Atmo-

sphere Packaging of Horticultural Commoditie,’’ in Ref. 3, pp.

175–206.

8. D. Zagory, ‘‘Ethylene-Removing Packaging’’ in Ref. 1, pp. 38–

54.

9. D. Faubion and A. A. Kader, Evaluation of Two New Products

with Claimed Ethylene Removal Capacity,’’ Perishables

Handling 86, 27–28 (1996).

10. S. Urushizaki, ‘‘Development of Ethylene Absorbable

Film and Its Application to Vegetable and Fruit Packaging,’’

Autumn Meeting of Japan Society for Horticultural,

Science Symposium: Postharvest Ethylene and Quality

of Horticultural Crops, University of Kyushu, October 8,

1987.

11. M. L. Rooney, R. V. Holland, and A. J. Shorter, ‘‘Removal of

Headspace Oxygen by a Singlet Oxygen Reaction In A Poly-

mer Film,’’ J. Sci. Food Agric., 32, 265–272 (1981).

12. Landec Corporation. Web information. Available at http://

www.landec.com/technology.html., Accessed August 2007.

13. C. O. Gill, ‘‘MAP and CAP of Fresh, Red Meats, Poultry and

Offals,’’ in Ref. 3, pp. 105–136.

14. A. L. Brody, ‘‘Modiﬁed Atmosphere/vacuum Packaging of

Meat’’ in A. L. Brody, ed., Controlled/Modiﬁed Atmosphere/

Vacuum Packaging of Foods, Food & Nutrition Press, 1989,

pp. 17–37.

15. AMI. Webinformation. Available at http://www.meatami.com/

Content/PressCenter/factsheets/casereadymeatsmap.pdf. Ac-

cessed August, 2007.

16. D. M. Gibson and H. K. Davis, ‘‘Fish and Shellﬁsh Products in

Sous Vide and Modiﬁed Atmosphere Packs’’ in Ref. 3, pp. 153–

174.

17. G. Robertson, Food Packaging, Principles and Practice, Mar-

cel Dekker, New York, 1993.

18. L. S. Post, D. A. Lee, M. Solberg, D. Furgang, J. Specchio, and

C. Graham, ‘‘Development of Botulinum Toxin and Sensory

Deterioration during Storage of vacuum and Modiﬁed Atmo-

sphere Packaged Fish Fillets,’’ J. Food Sci. 50, 990–996

(1985).

19. J. P. Smith and B. K. Simpson, ‘‘Modiﬁed Atmosphere Packa-

ging of Bakery and Pasta Products’’ in Ref. 3, pp. 207–242.

20. F. Castelvetri, Proceedings of the Fourth International Con-

ference on Controlled/Modiﬁed/Vacuum Packaging, Decem-

ber 2–6, 1988. Glen Cove, New York, 1989 pp. 43–62.

21. T. Martens, ‘‘Current status of Sous Vide in Europe’’ in Ref. 3,

pp. 37–68.

22. A. A. Kader, D. Zagory, and E. L. Kerbel, ‘‘Modiﬁed Atmo-

sphere Packaging of Fruits and Vegetables,’’ CRC Critical

Rev. Food Sci. Nut. 28(1), 1–30 (1988).

23. K. L. Yam and D. S. Lee, ‘‘Design of Modiﬁed Atmosphere

Packaging for Fresh Produce’’ in M. L. Rooney, ed., Active

Food Packaging, Blackie Academic & Professional, 1995 pp.

55–73.

MODIFIED ATMOSPHERE PACKAGING

MARKET, EUROPE

EMMA HANBY

LYNNERIC POTTER

Campden and Chorleywood

Food Research Association,

Chipping Campden,

Gloucestershire, United

Kingdom

INTRODUCTION AND MAP MARKET INFORMATION

In the last few decades there has been a dramatic growth

in the chilled foods market in Europe. This growth has

been stimulated by an increasing consumer demand for

fresh, convenient, and additive-free foods. This consumer

demand has stimulated the growth of modiﬁed-atmo-

sphere packaging (MAP) as a technique to improve pro-

duct image, reduce wastage, and extend the shelf-life

quality of a wide range of foods. Also the added beneﬁts

of improved transportation and distribution chains and

longer product shelf life have enabled widespread use of

modiﬁed atmosphere packaging.

The prepared chilled foods market in Western Europe

is worth approximately 14.62 billion euros. The United

Kingdom leads the way, with 54% of the chilled food

market, equating to nearly 8 billion euros, followed by

France with 18%. Other countries with increasing sales of

chilled prepared foods include Germany, Italy, Spain,

Belgium, and the Netherlands (1). Figure 1 illustrates

the segmentation of the chilled food market. Proportion-

ally more retail area is being devoted to chilled foods at the

expense of frozen and ambient-stable foods. The main

54%

18%

28%

United Kingdom

Other

France

Figure 1. Segmentation of the chilled food market, Europe.

794 MODIFIED ATMOSPHERE PACKAGING MARKET, EUROPE

reason for this development is that the concentration of

retail power in the United Kingdom is the highest in the

world, led by Sainsbury, Tesco, Morrisons, Asda, Waitrose,

and Marks & Spencer. Their operations are increasingly

being focused on centralized distribution and a quality

image that they feel is enhanced by an expanding chilled-

foods sector (2).

As MAP grows in popularity across Europe, some of the

more established MAP areas such as raw red meats, will

see their growth rates slow down. Centralized packing of

these types of products will become more common rather

than retailers cutting and packing the product in the back

of the store. MAP can allow a wider area for distribution

across Europe, thereby reducing costs, but packers need to

ensure that the product can outlast the distribution time

to the store. There has been a surge of interest of MAP in

the chilled ready meal market with products such as

sandwiches, salads, and cooked–chilled products. It is

predicted that the MAP chilled ready meal market will

dramatically increase in volume and value, and this

strong growth will cause it to overtake the frozen ready

meal market, particularly in the United Kingdom.

BACKGROUND INFORMATION

Modiﬁed-atmosphere packaging (MAP) is a popular food

preservation technique, whereby the composition of the

atmosphere surrounding the food is different from the

normal composition of air, which consists of oxygen

(20.9%), carbon dioxide (0.03%), and nitrogen (79%).

These gases can be used on their own or in combination

to enhance the shelf life and quality of the packaged

product.

Vacuum packing (VP) is the removal of most or all of

the air within a package without deliberate replacement

with another gas mixture.

Active packaging can be used in conjunction with MAP,

whereby certain additives are incorporated into the packa-

ging ﬁlm or within packaging containers and are capable

of altering the atmospheric composition surrounding the

food. Active packaging devices include oxygen and carbon

dioxide scavengers and ethanol and carbon dioxide

emitters.

Controlled-atmosphere storage (CAS) is yet another

food-preservation technique similar to MAP; but unlike

MAP, where there is no way of controlling atmospheric

constituents at speciﬁc concentrations once a package has

been hermetically sealed, in CAS the atmospheric consti-

tuents are precisely adjusted to speciﬁc concentrations

throughout the storage and/or distribution of perishable

foods. CAS is used primarily for the warehouse storage of

whole fruit and vegetables and for the road or sea-freight

container transport of perishable foods (3).

Gases Used for MAP

The gas mixture used in MAP must be chosen to meet the

needs of the speciﬁc food product (3), but for nearly all food

applications this will be some combination of either carbon

dioxide (CO

), oxygen (O

), or nitrogen (N

). For example,

raw red meats are often packed in a high oxygen environ-

ment to maintain the red color, bakery products will be

packed in a combination of carbon dioxide and nitrogen to

prevent mold growth and pack collapse, and dried goods

are packed in nitrogen to prevent oxidative rancidity.

Novel Gases

Novel gases such as carbon monoxide, ozone, nitrous

oxide, helium, argon and high oxygen have been used to

extend the shelf life of a number of food products. For

example, carbon monoxide has been shown to be very

effective at maintaining the color of red meats, maintain-

ing the red stripe of salmon, and inhibiting plant tissue

decay. However, carbon monoxide is not permitted in the

EU, due to its highly toxic and explosive nature. Argon

and nitrous oxide are known to sensitize microorganisms

to other antimicrobial agents (4). Argon has been shown to

inhibit tissue fermentation in sliced tomatoes, inhibit

protein breakdown in seafood, and extend the shelf life

of prepared fruit (5) and has been used as a replacement

for nitrogen. Research has also indicated that argon is

biochemically active, probably due to its enhanced solubi-

lity in water compared with nitrogen and oxygen and its

possible interference with cell membrane ﬂuidity and

enzymic oxygen receptor sites (4). Nitrous oxide is being

used as a propellant in whipped cream cans. The commer-

cial use of most of these gases is severely limited in the

United Kingdom because of regulatory constraints, safety

concerns, negative effects on sensory quality, or economic

factors (3). However, argon (E938), helium (E939), nitrous

oxide (E942), and sulfur dioxide (E220) are now permitted

for food use in the EU (4).

Research into high oxygen applications other than with

meat products has resulted in some commercial applica-

tions. High oxygen has been found to be particularly

effective at inhibiting enzymatically mediated discolora-

tion, preventing anaerobic fermentation reactions and

inhibiting aerobic and anaerobic microbial growth. Under

high oxygen MAP it is hypothesized that reactive oxygen

species damage vital cellular macromolecules and thereby

inhibit microbial growth when oxidative stresses over-

whelm cellular antioxidant protection systems (6). Re-

search carried out at Campden and Chorleywood Food

Research Association (CCFRA) found high oxygen MAP to

have beneﬁcial effects on the sensory quality of the vast

majority of the fresh produce items studied. These items

included a number of different types of lettuce, potatoes,

coriander, raspberries, and strawberries (7).

Products Packed Under MA

The United Kingdom is undoubtedly leading the world in

terms of the range of food products packed under MA (8).

These product developments have been prompted by the

major retail chains, which have considerable inﬂuence in

the British food industry (9). Established products packed

under MA include red meats, poultry, cooked and cured

meats, ﬁsh and seafood, pasta, cheese, bakery goods,

pizza, quiche, ready meals, dried foods, fruit, and

MODIFIED ATMOSPHERE PACKAGING MARKET, EUROPE 795

vegetables. Newer modiﬁed atmosphere products include

sandwiches, as well as fresh chilled combination products

with meat/ﬁsh and vegetables. Further developments

include products being modiﬁed atmosphere packed,

stored frozen, and then thawed to chilling for retail sale.

However, there is little background information on the

effects of freezing on the gases used in modiﬁed atmo-

sphere packaging.

Nitrogen and/or carbon dioxide are also used with a

number of beverages such as beer, lager, fruit juices, and

carbonated soft drinks.

Although retail products have tended to attract most of

the publicity in relation to MAP developments, bulk MA

technology is being used for products such as pork pri-

mals, poultry, and bacon (8). In addition, this technology is

presently being used to gas ﬂush conventionally packaged

retail products, such as overwrapped trays of red meats,

into large bag-in-box master packs. Excellent opportu-

nities also exist for using MAP technology for supplying

the catering, food processing, and wholesale industries

with bulk packs of many dried commodities, such as tea,

coffee, cocoa, herbs, spices, and nuts, as well as chilled

perishable foods (8).

MAP DEVELOPMENTS

High-Permeability Films for Produce

Unlike other foods that are MA packed, fresh fruit and

vegetables continue to respire after harvesting, and con-

sequently any subsequent packaging must take into ac-

count this respiratory activity. The depletion of O

and the

accumulation of CO

are natural consequences of the

progress of respiration when fresh fruit or vegetables

are stored in a hermetically sealed package. Such mod-

iﬁcation of the atmospheric composition results in a

decrease in the respiration rate, with a consequent exten-

sion in the shelf life of fresh product. However, packaging

ﬁlm of the correct permeability must be chosen to realize

the full beneﬁts of MAP for fresh produce.

Typically, the key to successful MAP of fresh produce is

to maintain an equilibrium MA (EMA) containing 2–10%

and CO

within the package. For highly respiring

produce such as mushrooms, beansprouts, leeks, herbs,

peas, and broccoli, traditional ﬁlms such as LDPE, PVC,

EVA, and OPP are not sufﬁciently permeable. Highly

permeable microperforated ﬁlms for highly respiring pro-

duce are more suitable. P-Plus ﬁlm can be microperforated

to match the permeability of the ﬁlm with the product’s

respiration rate.

Intellipac

technology is a means of providing different

permeabilities to maintain the optimum atmosphere

within a pack even with changing temperatures. The

membrane patch that is attached to a hole in the ﬁlm

controls the ﬂow of gases in and out of the pack by altering

the properties of the polymers within the membrane (10).

Seal Integrity of MA Packs

Seal integrity is important to maintain a safe and good-

quality product. A number of methods can be used to

detect leaks in MA packs. Ofﬂine methods include the

following:

1. Dye testing. A penetrative dye is sprayed or painted

onto the seal area. This indicates if a leak is present

and also identiﬁes the position.

2. Gas Analysis. This can be used on ﬂexible packs to

determine whether there is a leak in the sealing

area (11). EMCO has established a European com-

pany that has the distribution rights of Oxysense O

technology. This can also be used as a noninvasive

detection device. The O

xysenset 4000 is a portable

oxygen analyzer that utilizes a noninvasive optical

method that determines oxygen concentration by

measuring the ﬂuorescent energy released from an

illuminated oxygen-sensitive sensor (O

xyDott)

(11).

3. Indicators. This is a nondestructive method for

detecting leaks in MA packs. Indicators give a visual

indication (e.g., a color change), if a leak is present.

For modiﬁed atmosphere packs the indicators used

are oxygen or carbon dioxide, depending on the gas

composition of the pack.

Carbon dioxide leak detectors can also be used where at

least 10% of the packs gas composition is CO

. These

systems can be ofﬂine or online and use CO

as a trace gas

to detect leaks.

Easy-Opening/Resealable Systems

A visit to any European supermarket will illustrate the

enormous growth in convenience foods. Clearly, the ease of

opening of these products is a key attribute. Also as the

population ages, and consequently their abilities to read

and/or handle food packages decreases, there is a need to

understand how consumers manage so-called easy-to-

open packaging and also to have an understanding of

how reducing seal strengths to make packs of all types

easier to open may compromise the quality and safety of

the products on sale. Easy-open features are not only

important for the convenience food market but are essen-

tial for the elderly and those with disabilities. Easy open-

ing and resealable systems are very different. Easy

opening systems are designed to aid consumers when

opening packaging, whereas resealable packs are de-

signed to help extend food shelf life in the consumer’s

home. However, once the primary seal is broken, the major

beneﬁt of MA to extend food shelf life is lost. The reseal-

able features such as slider/zipper will just provide the

convenience beneﬁt to the consumer and will prevent

moisture loss of the product.

There are a variety of systems now available, including

peelable ﬁlms for easy opening and zips/slider (single- or

dual-track zipper) to reclose bags after opening.

Valle Spluga Two-Phase MAP

When packing high-moisture/high-fat foods such as

meat, poultry, and seafood, the high solubility of CO

these foods can lead to pack collapse, due to the decrease

796 MODIFIED ATMOSPHERE PACKAGING MARKET, EUROPE

in headspace volume (10). In conventional retail MA

packs, pack collapse is minimized by limiting the pro-

portion of CO

to less than 40% and having a large

headspace volume above the food. However, these proce-

dures limit the shelf-life extension potential since lower

levels of bacteriostatic CO

are maintained within MA

packs. Additionally, the larger headspace volume required

results in a decreased packing density, with asso-

ciated higher costs of production, storage, and distribu-

tion (8).

An innovative process for solving the problem of pack

collapse is now widely used. This two-phase process is

based on the use of solid and gaseous CO

in MA packs (7).

A weighed tablet of solid CO

is dispensed into a thermo-

formed tray containing the food product, just before gas

ﬂushing and sealing. The solid CO

sublimes to gaseous

after sealing and causes the semirigid package to

swell. However, after a few hours, an equilibrium is

established between the gaseous CO

in the headspace

and the CO

absorbed by the food, and hence the package

reverts to its original shape. Valle Spluga patented the

process and has successfully used this process to market

spring chickens in MA packs that maintain high levels of

with a minimum headspace (8).

GUIDELINES FOR THE MANUFACTURE AND HANDLING

OF MA PACKED FOODS

MA-packed chilled foods have been marketed in Europe

for many years, and during this period they have main-

tained an excellent safety record, providing the consumer

with high-quality, safe, and fresh products. It is impor-

tant, however, for all those involved in the manufacture

and handling of MA-packed chilled foods to be vigilant

about possible food safety hazards, especially in the light

of increased regulatory and consumer concern about

the perceived rise in food poisoning incidents. It is im-

perative that the food safety of such products not be

compromised by complacency and poor manufacturing or

handling practices. Such a situation would seriously com-

promise the safety of MAP technology and hence its

further application as a preservation technique for chilled

foods (3).

REPORT ON VACUUM PACKAGING AND ASSOCIATED

PROCESSES

The UK Advisory Committee on the Microbiological Safety

of Food (ACMSF) has published a report on the potential

hazards of vacuum packaging and associated processes

such as ‘‘sous vide’’ and MAP (12). Emphasis is placed on

the safety aspects of chilled foods, with particular refer-

ence to the risks of botulism. Preventative measures have

been identiﬁed, and possible mechanisms for control have

been detailed. Among the many recommendations is one

which states that chilled prepared food packed under

reduced O

levels with an assigned shelf life of more

than 10 days should contain one or more controlling

factors in addition to chill temperatures to prevent growth

and toxin production by Clostridium botulinum. Control-

ling factors include heat treatment, acidity and salt levels,

and water activity. The UK government endorses this

recommendation and has drawn it to the attention of

appropriate trade and professional bodies.

CONCLUSIONS

MAP is still one of the most exciting and innovative areas

of the packaging industry. New developments in both

packaging materials/machinery and food product applica-

tions are being described at an ever-increasing rate. The

biggest growth areas are likely to be in easy-opening MA

packs and methods for measuring integrity. The MAP

chilled-food market in Europe is substantial and has

enjoyed considerable growth in recent years because of

the important beneﬁts it provides to food manufacturers,

retailers, and consumers alike. Although MAP has been

used primarily for red meats, tremendous opportunities

exist for the MAP of other foods.

BIBLIOGRAPHY

1. www.food and drink europe.com

2. R. Pearson, ‘‘The Quiet Revolution. Imperial Chemical Com-

pany,’’ Plast. Today 29 (1988).

3. B. P. F. Day, Guidelines for the Manufacture and Handling of

Modiﬁed Atmosphere Packed Food Products, CCFRA Techni-

cal Manual 34, Chipping Campden, Gloucestershire, UK,

1992, p. 3.

4. B. P. F. Day, ‘‘Novel MAP for Fresh Prepared Produce,’’ Eur.

Food Drink Rev. 1, 73–80 (1996).

5. K. C. Spencer, ‘‘The Use of Argon and Other Noble Gases for

the MAP of Foods,’’ paper presented at International Con-

ference on MAP and Related Technologies, CCFRA, Chipping

Campden, Gloucestershire, UK, September 6–7, 1995.

6. M. I. Gonzalez and B. P. F. Day, The Effects of Novel Atmo-

sphere Packaging (MAP) on Fresh Prepared Produce Growth,

in Proceedings of the Cost 915 Conference, Cuidad Universi-

taria, Madrid, Spain. October 15–16, 1999.

7. B. P. F. Day, Fresh Prepared Produce: GMP for High Oxygen

MAP and Non-sulphite Dipping, CCFRA Guideline No. 31.

Chipping Campden, Gloucestershire, UK, 2001, pp. 70–75.

8. B. P. F. Day, ‘‘Recent Developments in MAP,’’ Eur. Food Drink

Rev. 2, 87–95 (1993).

9. B. P. F. Day, and L. G. M. Gorris, ‘‘Modiﬁed Atmosphere

Packaging of Fresh Produce on the Western European Mar-

ket,’’ ZFL 44(1/2), 32 (1993).

10. G. Robertson, Food Packaging Principles and Practice, 2nd

edition, CRC press, Taylor & Francis Group, Boca Raton,

2006, pp. 285–311.

11. L. Potter, E. L. Lloyd, and A. J. Campbell, The Manufacture

and Integrity of Seals for Packaged Foods, CCFRA Review 48,

Chipping Campden, Gloucestershire, UK, 2006, p. 23.

12. ACMSF, Report on Vacuum Packaging and Associated Pro-

cesses, Advisory Committee on the Microbiological Safety

of Food, HMSO, London, 1992.Information emanating from

this Research Association is given after the exercise of all

reasonable care and skill in its compilation, preparation, and

issue, but is provided without liability in its application and

use.

MODIFIED ATMOSPHERE PACKAGING MARKET, EUROPE 797