Modified atmosphere

Modified atmosphere

Modified atmosphere

is the practice of modifying the composition of the

internal atmosphere of a

package

(commonly food packages, drugs, etc.)

in order to improve the

shelf life

.

The modification process often tries to lower the amount of

oxygen

(O

2

),

moving it from 20.9% to 0%, In order to slow down the growth of

aerobic

organisms

and the speed of

oxidation

reactions. The removed oxygen can

be replaced with

nitrogen

(N

2

), commonly acknowledged as an inert gas,

or

carbon dioxide

(CO

2

), which can lower the

pH

or inhibit the growth of

bacteria

.

Carbon monoxide

can

be used

for keeping the red color

of meat.

Re-balancing of gases inside the packaging can be achieved using active

techniques such as gas flushing and compensated vacuum or passively by

designing

“breathable”

films

know

n

as

equilibrium

modified atmosphere

packaging (EMAP). Packets containing

scavengers

may be used.

MAP = Modified atmosphere packaging

?

EMAP = Equilibrium modified atmosphere packaging

?

MA/MH = Modified atmosphere/modified humidity packaging

?

Controlled Atmosphere

Storage (CAS) was used already In the 1930s when

ships transporting fruits had high levels of CO

2

in their holding rooms,

thus increasing the shelf-life of the product. In the 1970s MA packages

reached

the

stores

when

bacon

and

fish

were

sold

in

retail

packs

in

Mexico.

Since then the development

has been stable

and the interest into MAP

has

grown

due

to

consumer

demand.

This

has

led

to

advances

for

example

in

the

design

and

manufacturing

of

Bacon

films.

New

techniques

are

designed,

like

the use of

anti-fogging layer

to improve product visibility. From MAP a

new packaging technique

?

EMAP has been developed.

Under

MA

products

like

red

meat

,

seafood

,

minimally

processed

fruits

and

vegetables

,

pasta,

cheese,

bakery

goods,

poultry,

cooked

and

cured

meats,

ready

meals

and

dried

foods

are

packaged.

The

three

major

commodity

types

are fruits and vegetables, meat and meat products, and seafood. It has

been

estimated

that

25-40%

of

all

fresh

produce

harvested

will not

reach

the consumers table, due to

spoilage

and mishandling that occurs during

distribu tion.

[

citation needed

]

[

edit

] Modified Atmosphere Packaging (MAP)

Modified Atmosphere

Packaging

(MAP) is a technique used for prolonging

the shelf-life period of fresh or minimally processed foods. In this

preservation technique the

air

surrounding the food in the package is

changed to another composition. This way the initial fresh state of the

product

may

be

prolonged.

It

is

the

shelf-life

of

perishable

products

like

meat, fish, fruits and vegetables that will be prolonged with MAP since

it

slows

the

natural

deterioration

of

the

product.

MAP

is

used

with

various

types of products, where the mixture of gases In the package depends on

the type of product, packaging materials and storage temperature. Meat

and fish need very low gas permeability films so for non-respiring

products (meat, fish, cheese etc.) high barrier films are used. The

initial

flushed

gas-mixture

will

be

maintained

inside

the

MA

package.

But

fruits

and

vegetables

are

respiring

products

where

the

interaction

of

the

packaging

material

with

the

product

is

important.

If

the

permeability

(for

O

2

and CO

2

) of the

packaging film is

adapted to the products respiration,

an

equilibrium

modified

atmosphere

will

establish

In

the

package

and

the

shelf-life of the product will increase.

[

edit

] Equilibrium modified atmosphere

packaging (EMAP)

Among

fresh-cut

produce

Equilibrium

Modified

Atmosphere

Packaging

(EMAP)

is

the

most

commonly

used

packaging

technology.

When

packaging

vegetables

and fruits the gas atmosphere of package is not air (O

2

21%; CO

2

0.038%;

N

2

78%)

but

consists

usually

of

a

lowered

level

of

O

2

and

a

heightened

level

of CO

2

. This kind of package slows down the normal respiration of the

product

to

prolong

its

shelf-life.

Of

course

there

are

other

factors,

like

the

size

of

the

product,

severity

of

preparation,

maturity

of

the

product

and

type

of

tissue

that

have

an

effect

to

the

shelf-life

of

an

EMA

packaged

produce.

[

edit

] Technology

There are two techniques used in the industry to pack vegetables namely

gas- flushing

and

compensated vacuum

. In gas-flushing the package is

flushed with a desired gas mixture, as in compensated vacuum the air is

removed totally and the desired gas mixture then inserted. The label

example of a gas mixture used for non-vegetable packaged food (such as

crisps

) is 99.9%

nitrogen

gas, which is inert at the temperatures and

pressures the packaging is subjected to.

[

edit

] Gases