PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
73
Chapter
4
PLASTICS BASED
PACKAGE FORMS &
SPECIALITY PACKAGING
FOR FOOD PRODUCTS
H S Sathish
Food Packaging Technology Department
Central Food Technological Research Institute
Mysore 570 020 (INDIA)
PLASTICS IN FOOD PACKAGING
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Chapter 4
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
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Chapter 4
PLASTICS BASED PACKAGE FORMS
AND SPECIALITY PACKAGING
FOR FOOD PRODUCTS
Plastic materials are synthetics made from
oil, coal or natural gas and are now one of the
principal packaging materials being used in
the form of wraps, pouches, bags, sacks,
bottles, jars, tubes, trays, and boxes. Plastics
have applications in transport packaging
too, where they have replaced steel, wood
and glass. They are also used in the form of
stretch wrapping and shrink wrapping and
shrink film, and as strapping for securing
palletized loads. There will be many other
packaging openings in the future for this
group of materials. The properties of plastics
like pliability, flexibility, formability and
ease of handling will enable plastics to
expand their position in the market against
competition from other materials such as
natural fibers, glass and metal.
Speciality packages which possess
certain functional properties to enable
processing and/or preservation of food
products include retort pouches/trays,
aseptic packages, modified atmosphere
packages, frozen and oven proof packages
and active and smart packaging.
New plastics, along with new combinations of natural and synthetic materials,
will undoubtedly continue to be developed
in the form of co-polymerized, laminated
and co-extruded packaging products to meet
a wide range of needs.
FLEXIBLES
Fig. 4.1. Flexible films and laminates
PLASTICS IN FOOD PACKAGING
Flexible films are basically produced
through extrusion, extrusion blowing and to
some extent through moulding. Flexible films
are used to make wraps, pouches, bags, and
their variations.
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WRAPS
Probably the simplest type of flexible
package ever devised is the intimate wrap,
where a sheet material is used to enclose a
quantity of product. The wraps are most
widely used in bakery and confectionery
industry. Metalised films and composite
materials in the form of twist wraps, Pleated
bunch wraps and folded wraps are
commonly used methods of wrapping.
flexibles are widely used in food industries
particularly for bulk packaging applications.
Flexible pouches are used to pack foods
such as: processed, frozen and fresh meats,
poultry and seafood; dairy foods, frozen
vegetables, dry bakery goods, coffee, tea,
candy and snack foods; dry powders;
prepared entrees and processed fruit and
vegetables; condiments and liquids; and
cereals and pet foods. Flexible pouches
being light weight and adaptable are
competing favorably with other containers,
such as glass and plastic bottles, metal and
composite cans and paperboard boxes.
Following are the commonly used pouch
styles.
Fin Pouch
Fin pouch is made by simply folding the
web material in half and sealing both sides.
The bottom sometimes also has a seal
depending on web material and product.
Fin pouches with an applied re-closeable
zipper are also popular. Liquids and
powders are generally packed in this
package style.
Gusset Pouch
Fig. 4.2. Bread wrapping
POUCHES
Pouches are totally enclosed packages
which are intended to hold the product with
or without assistance.
Flexible pouches can be made either from
monolayers or multilayered by laminates or
co-extruded structures. Metalization on
plastic films to improve the barrier properties
and opacity is also common. Also composite
Gusset pouch is formed by folding the
web material into a “W” shape at the bottom
of the pouch. By adapting the fin pouch style
to have a gusset at its base, the fill volume of
the pouch is increased.
Stand Up Pouch
Stand Up Pouch has proved to be one of
the most successful means of packaging a
wide variety of products. The method of
producing the Stand Up pouch is very
similar to making a gusset pouch with the
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
addition of sealing the edges and bottom of
the gusset in order that the pouch will stand
upright on the store shelf. The style is ideal
for snack foods, pet treats, delicate products,
dried soup mixes, condensed soups and
other liquids.
Membrane Pouch
The membrane pouch concept was
designed for separating a fin, gusset or stand
up pouch into two separate compartments
by means of a center web. Membrane pouches
are used for separating any two ingredients
from each other prior to dispensing from the
pouch.
Tandem pouch configuration is ideal for
increasing output of a single product fill,
increasing output of a multi-product fill or
the presentation of a two part product in
separate packages. Pouches may remain
Frangible pouch
attached with a perforation or serration. They
can also be cut into individual pouches after
discharge from the pouching machine.
Frangible Pouch
The frangible pouch is used for keeping
two components separate from one another
prior to being mixed them within the pouch
itself. The two components are kept separate
until one of the compartments is squeezed
and the resulting pressure ruptures the seal
between the compartments and allows the
components to mix. After mixing, the pouch
is opened and the product is dispensed.
Bags
Tandem Pouches
Fin pouch
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A plastic bag is defined here as a bag
manufactured from extensible film by heat
sealing one or more edges. They are produced
in different sizes for use in different
packaging applications. The plastic bags
are identified by the type of heat seals
Gusset pouch
Membrane pouch
Fig. 4.3. Different pouch styles.
PLASTICS IN FOOD PACKAGING
Stand up pouch
Tandem pouch
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Chapter 4
employed. There are basically three types of
seal methods in use and they are: side weld,
bottom-seal, and twin seal. Plastic bags,
available in virtually all shapes, sizes and
colours and configurations have replaced
paper in most light duty packaging
applications. Polyethylene such as LDPE,
HDPE, HMHDPE and polypropylene are
the most commonly used materials for bags.
Bags are generally classified as commercial
bags and consumer bags. Commercial bags
are used as a packaging medium for another
product, whereas consumer bags are used to
contain the purchased materials from the
market.
container, usually holding one but sometimes
more than one bag.
Edible oils packed in bag-in-box are very
popular in the market. Other products being
packed in this system are fruit juices and
non-carbonated beverages. Both hot fill and
aseptic filling techniques can be used. Other
liquid products that are being used in bagin-box include water, milk, wine, cider,
vinegar, soya sauce, tomato ketchup, salad
dressings, etc. Bag-in-box is not just confined
to small packs and packs up to 1,000 liter
capacity are also in the market. The bag-inbox technique was originally used for liquids
but has successfully diversified into
packaging of dry powdered or granular
products. The typical materials used for the
construction of bag are Kraft/PE/Foil/PE,
Bleached Kraft/PE/Foil/PE and PET/PE/
Foil/PE.
Fig. 4.4. Plastic bags
Bag-in-Box
Bag–in-box is a two package system used
for commercial packaging of food and nonfood products. It is used in bulk packaging
of liquid and semi liquid products consisting
of three main components. (1) a flexible,
collapsible, fully sealed bag made from one
or more plies of plastic films; (2) a closure
and a tubular spout through which contents
are filled and dispensed; and (3) a rigid outer
corrugated or solid fibreboard box or
Fig. 4.5. Aseptic bag in a box.
Skin Packs
Skin packaging is another form of blister
packaging. In skin packaging, the product
itself is the mould over which the heated
plastic film or a “skin” is drawn by vacuum
and heat sealed to paperboard card. There
are three principal components associated
with skin packaging: the plastic film, the
heat seal coating and the paperboard card.
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
There are three types of films used in skin
packaging: LDPE, PVC and Surlyn Ionomer.
Normally, skin packaging films are heated,
draped and formed, and bonded to the
paperboard card in one operation.
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l Automation
l Scan through optics
l Ease of removal
l Recycling
Stretch packaging operation consists of
stretching the film around the objects to be
wrapped and then heat sealed. The residual
tension in the film provides the tight contour
wrap. Again, like shrink wrapping, it finds
its use in collating, pallet overwrapping and
retail wrapping.
The main films used in stretch wrapping
are LDPE, EVA and PVC. The choice of stretch
film depends on factors such as appearance,
protection required and the susceptibility to
damage by compression of the articles to be
wrapped.
Fig. 4.6. Skin packaging of chicken
sausages.
Stretch Films
Stretch films are basically used to unitise
smaller individual items into a larger unit
loads. The advantages of unitization are:
l Reduced handling costs
l Less manpower requirement
l Transportation savings
l Protection to the commodities.
In addition to the above advantages,
stretch films offer further advantages:
l Low supply cost
l Protection from moisture, dirt and
abrasion
l Reliable performance
PLASTICS IN FOOD PACKAGING
Stretch wrapping of pallet load is done by
spiral winding so that a standard width of
film can be used, irrespective of the pallet
load dimensions. Pallet stretch wrap
equipments are also available for this
purpose.
Shrink Films
Shrink films are basically used to wrap
awkwardly shaped articles, which
otherwise are difficult to pack. The
availability of tougher, cheaper films with
higher softening points such as LDPE, PVC
along with hot air shrink tunnels made shrink
packaging a reality. The applications include
collation of cans, jars, bottles or cartons. For
cans, bottles and cartons, it is necessary to
use fibreboard trays or plastic trays such as
PVC or EPS. Cost-wise, shrink wrapping is
cheaper compared to fibreboard boxes.
The use of shrink film at retail store level
has a positive impact from the environmental
point of view. The amount of packaging to be
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Chapter 4
disposed off at retail level is smaller
compared to paperboard packaging, and
this is an important positive point from the
environmental point of view.
Overwrapping of complete pallet loads
displacing the use of paper or board
coverings held in place by metal or plastic
strappings by shrink wrapping ensures more
stability than strapped loads and this
provides extra protection against ambient
conditions.
conventional flat looms.
l Improved strength of the weaving fabric.
l Savings in floor space, number of
operations and labour.
l Higher output of sacks.
Advantages of Woven Sacks
over Conventional Sacks of
Jute, Paper, etc.
l Weighs only 20% of the jute sacks.
l Resistant to even most corrosive
products.
l Safe for direct contact with food products
and do not cause contamination as likely
with jute fibres.
Fig. 4.7. Shrink wrapping of aseptic
fruit juice packages and HDPE container.
Plastic Woven Sacks
Woven sacks are manufactured by
weaving of monoaxially oriented tapes of
HDPE, PP and LDPE for packaging of
foodgrains, sugar, rice, salt, milk powder,
onion, potato, etc.
For high moisture sensitive foods, where
higher barrier properties are required, loose
liners of LDPE, LLDPE or HMHDPE are
used or LDPE lamination of the woven fabric
is done before stitching into sacks.
Advantages of Circular Woven
Sacks
l Coverage is very much better because the
tapes do not get twisted as in flat weaving.
l Savings up to 25% because of superior
coverage.
l Much higher output compared to the
l Are water repellent and can be made
water and moisture-proof by using a loose
liner or lamination.
l Do not contain Jute Batching Oil (JBO).
l No corrosion even in presence of water or
in corrosive atmosphere.
l Superior drop impact properties; as such
bursting losses are very low or almost
nil.
l Resist fungal attack.
l Can be manufactured in any desired
colours for easy identification as well as
for the brand image.
l Attractive printing.
l Clean appearance.
l Easy disposability and reusability.
Possible Variations
l Leno bags for the packaging of potatoes,
onions, apples, fruits, etc — fabric is
open mesh with average weight of less
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
than 30 g/m2. For example, a 40 kg potato
bag weighs only 28 g each.
l Fabric can be laminated to paper for
Plastic film.
l Medium size bulk containers up to 2 ton
capacity are manufactured using a fabric
weighing 200-250 g/m 2 from UV
stabilized PP Tapes.
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Plastic netting is a valuable packaging
means. It is resilient, strong, and flexible.
Netting can be frozen and then heated or vice
versa, keeping its strength and flexibility.
Plastic netting is very cost effective compared
to other forms of packaging and is recyclable.
Plastic netting is used in many packaging
applications. As a flexible material it
conforms to irregular products. Netting
provides an excellent packaging media as a
decorative and protective overwrap. Netting
has wide applications in the packaging of
fresh fruits and vegetables especially root
vegetables and in the poultry industry.
Fig. 4.8. Plastic woven sacks.
Nettings
Plastic nettings are produced either by
knitting or by extrusion. Netting is produced
in the form of tube and sheet in a wide variety
of mesh sizes, diameters, width and colours.
Extruded netting is produced through
counter rotating dies. As the inner and outer
dies rotate, small strands of molten plastic
overlap each other, bonding themselves
together where they overlap. The material is
heated and stretched to the point just before
breakage to get the orientation. Knitting
machines offer simple and sophisticated
stitch patterns. HDPE and PP are the most
commonly used plastic materials for
nettings.
PLASTICS IN FOOD PACKAGING
Fig. 4.9. Potatoes and onions
in plastic netting
RIGID AND SEMI-RIGID
CONTAINERS
Bottles and Jars
When used to make jars or bottles, plastics
have some distinct advantages over glass or
metal including the following:
l Non breakability: At least most plastics in
many applications are less likely to break
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on impact than glass. With most
commercial plastics, unbreakability is a
major advantage.
Fig. 4.10. Plastic bottles and jars in
various shapes and sizes.
l Lighter weight: As low as 1/3 the weight
of metal and 1/8 the weight of glass in
comparable applications.
l Lower noise level in packaging and in
use, again compared to glass and metal
no corrosive as opposed to metal cans.
l Transparent: Some plastics–when compared to metal.
l Smaller size: When compared to glass,
wall thickness for equivalent strengths
and volumes are less, and so equivalent
contents can be contained in packages of
smaller exterior size.
l Flexibility of forming: Capital investment
required to produce rigid plastic
containers is only a small fraction of that
required for glass or metal.
The major plastic materials used for
bottles and jars are HDPE, LDPE, PP, PVC,
PS, PC, PET, Multilayers of desired
combinations.
bottles offer new packaging possibilities for
improved barrier requirements with a
potential to replace traditional glass and
metal containers. A wide range of different
polymers can be combined in different ways,
and also the wall thickness of the individual
layer can be optimized to achieve the
necessary functionality and offer the best
economics. Manufacture of these bottles
involves use of flexible co-extrusion
machines suitable to rheological behaviour
of the different polymers as well as quality
control.
Co-extruded bottles are already in the
market for a wide range of foods such as
ketchup, sauces and jellies. These bottles
have replaced glass bottles and they are
unbreakable, squeezable and light weight.
Co-extruded Blow Moulded
Multilayer Bottles
Co-extruded blow moulded multilayer
Fig. 4.11. Co-extruded multilayer plastic bottles.
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
The most popular material combination in
use today is the six layer combination – PP or
HDPE/regrind/adhesive/EVOH/
adhesive/PP or HDPE. Another three layer
combination is PC/PET/PC. Here, no
adhesive material is required , since both
polymers belong to the polyester family and
have excellent adhesion.
Stretch Blow Moulded Bottles
The hollow type of extrusion blow
moulded bottles made of various thermoplastics like LDPE, HDPE, PVC, PS, PC, etc.
have been in commercial use for over three
decades. However, the biggest breakthrough
in bottle making was the invention of stretch
blow moulding technique since it provides
material savings, improved clarity and good
mechanical strength. Following are the
advantages of stretch blown moulding:
l Raw material savings up to 25% since
thinner walls are possible because of
superior mechanical strength due to
biaxial orientation.
l Improved clarity particularly in case of
PET bottles.
l Improved barrier properties.
equivalent performance, and container
weight and cost can become excessive. Heat
resistance is another important property
required by the can to undergo pasteurization and sterilization for most of the acid
and low acid food products. A precise flange
is needed to guarantee a perfect seal, which
is absolutely critical for sterilized cans, and
certainly desired for contained liquids,
especially under pressure. Plastic ends or
metal ends are used in these type of cans.
Another design concern is the necked-in end
now customary for beverage cans, which
allows tighter six packer and cheaper ends.
This can be done with plastics, but mould
design is more complicated to permit the
undercut needed.
These cans have huge applications in
softdrink and beer markets. Thermoformed
and blow moulded PET bottles coated with
PVDC are in the market in USA, Britain and
Italy. For heat resistance PP is the most
suitable material. However, PC can also be
used but it is expensive. For better barrier
properties, a multilayered co-extruded PP/
EVOH/PP can also be used. Injection
moulded HDPE and PS cans are also in use
for some food products.
l Improved mechanical properties.
The major materials that are processed by
this process are PET and PVC followed by
PP. Thermoforming is another technique
used for making jars.
Cans
Cans are also made by plastics, by
injection moulding, blow moulding and
thermoforming. Since plastics are not as
rigid as metals, thicker walls are needed for
PLASTICS IN FOOD PACKAGING
83
Fig. 4.12. Plastic can with metal lid.
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Chapter 4
Collapsible Tubes
Many plastics can be used to make plastic
tubes, but LDPE/HDPE is the primary
material used today. It has high moisture
barrier properties, low cost and good
appearance. Its lack of oxygen and flavor
barrier have been improved with barrier
coatings. HDPE and PP are also used, but
they are much stiffer than LDPE for tube side
walls, and hence not as popular as LDPE.
EVOH based co-extruded tubes offer excellent
barrier to oxygen and flavour.
These tubes are produced by Strahm and
Downs method, basically an extrusion
process. The collapsible tubes are corona
treated during extrusion for better ink
adhesion during printing. HDPE and PP
screw caps are used as closure for collapsible
tubes. At present, the all plastic barrier tube
is not economically viable with a laminated
structure. Plastic collapsible tubes will find
a major share in the market, in the event of
reduction of EVOH prices in the future.
In the open-head design configuration,
the containers are usually supplied with a
removable lid designed to be used with either
liquids or solids. The lids are available with
spouts of various types. The most commonly
used pour fittings for liquids is the flexible
polyethylene spout. This fitting snaps into
position in a preformed hole or is a spout
that incorporates metal collar that is crimped
onto a formed, ridged opening in the lid. The
open head pails are generally non-vertical
and are nested into each other for efficient
storage and transportation, prior to being
filled and sealed. In the closed-head
configuration, no nesting advantage exists.
The size of pails varies from 3 L to 25 L
capacity. Both open-head and closed-head
pails are made from HDPE. These pails are
universally injection moulded.
Fig. 4.14. Plastic pails for vanaspati
Fig. 4.13. Collapsible plastic tubes
Pails
Plastic pails are open head containers
with removable lids and containers
produced as a single unit called tight head
containers. The container top or lid can be
manufactured with one or more openings
for filling and dispensing. The openings are
designed to be used with a variety of closures.
Blister Packs
Blister packs are the fastest packing
method world over. It consists of combination
of plastic materials with paperboard to
produce visual, self vending packages. The
rapid growth of self service retailing created
a demand for innovative packaging that
protects the product and also provides sales
appeal in terms of product visibility and
instruction for use. The size and shape are
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
numerous because of the flexibility it offers.
The blister packs consists of a preformed
plastic blister, paperboard and a heat sealing
coat on the paperboard. The selection of
packaging material for blister in terms of
type, thickness and grade depends on many
factors like height and weight of the product,
sharp and pointed edges of the product, heat
sealing properties, compatibility with the
product and machinability. The most
commonly used plastic materials for blister
packs are PVC, PVDC coated PVC, OPS and
recently PET is also being used.
Heat seal coatings provide a bond
between the plastic blister and the printed
paperboard card. These solvent or water
based coatings can be applied to rolls or
sheets of printed paperboard using roll
coaters, gravure or flexographic methods.
Paperboard of thickness between 0.45 and
Fig. 4.15. Artificial sweetener in a
blister pack
PLASTICS IN FOOD PACKAGING
85
0.60 mm in generally used. The normal
sequence of assembly involves loading the
blister with product, placing the paperboard
card over the blister and heat-sealing the
package.
Thermoformed Containers
Tubs, trays and box inserts are the
commonest containers formed by this method
particularly where very thin walls are
required, such that it would be difficult for a
polymer to flow between the mould walls in
an injection moulding.
PS, Polypropylene, PVC, HDPE, and PET
have all been used for thermoformed
containers. The latest materials in this field
are foamed polystyrene andPP, which can
be thermoformed to give trays and containers
with built in cushioning properties. The
thermoformed articles are produced either
by vacuum forming or by pressure forming.
Continuous on-line Thermo-Form-FillSeal (TFFS) machines are also available in
the market. This type of machine uses a reel
fed web of plastics material into which is
thermoformed a series of tray like
depressions. The depressions are indexed
forward as a web and after filling a further
web is fed over the open top of the filled tray
and sealed on to the flanges of the trays to
form a closure. The web of filled and closed
trays is then punched to form individual
packs, or slit into partially jointed strips
containing several units. Lidding materials
can be plastic film or film laminations,
although metal foil reverse coated for heat
sealing to the container is more widely used.
Re-closable plastic lids can be provided for
some thermoformed containers, either by a
separate operation or by on-machine
thermoforming at the lidding station.
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Chapter 4
The products, which are commonly
packaged in thermoformed containers, are
butter, cream, yogurt, processed cheese,
ready-to-eat foods, fruits, vegetables, and
jams.
Use of thermoformed cups made of
polypropylene are widely used. These have
functional advantage of transparency and
toughness over HIPS cups. These can be
used for packing Dairy products and
drinking water.
Fig. 4.16. Thermoformed trays of
various shapes and sizes.
Drums
Open top plastic containers up to 25 L
capacity are called jars or pails. The term
“Drum” applies to containers larger than 25
L capacity, and the container can be either
open or closed type. The standard drum
sizes commonly used are 30, 60, 120 and 216
L. The development of large plastic drums
took many years because they required
special resins and processing equipment.
These drums are used in food processing
industries for the shipment and storage of
products that include concentrated fruit
juice, vegetable pulps and condiments. They
are made by extra high molecular weight
high density polyethylene. These have
relatively high resistance to permeation,
which can be further improved by using
higher wall thickness. The service life of
HDPE drums cannot be predicted because it
largely depends on climatic conditions.
Different colorings, especially black, blue,
green, white and gray, increase resistance to
weathering and protect the product from
light. Depending on the climatic conditions
additional UV stabilizers must be added.
Drums are manufactured by rotational
moulding. In this process, a fine powder or
Fig. 4.17. Food products in thermoformed
containers
Fig. 4.18. Plastic drum and milk cans
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
liquid thermoplastic takes on the shape of a
heated mould subjected to tri-axial total
rotation. Once the receptacle has been
formed, the mould is cooled and opened. The
particle size of the powder used also affects
the surface appearance, the quality of which
improves with the fineness of the powder.
Crates
Plastic crates are being used for many
years in the food industries as returnable
shipping containers. The more familiar uses
have been as milk crates, fresh fruits and
vegetable crates, beverage cases, as a storage
container in factory warehouses, etc.
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moulding. This method is most suited for
reusable shipping container because it allows
intricate shapes to be moulded at high rates
of production. HDPE is the most commonly
used material for plastic crates. There are
four different types of crates available:
l
Nest only
l
Stack only
l
Stack and nest
l
Collapsible
Corrugated Sheets & Boxes
Plastic corrugated boxes are used in
situations where the traditional paper based
CFB are inadequate in certain situations.
Theoretically, it is possible to use all plastic
materials for conversion into corrugated
sheets, but the costs can be prohibitive. The
most commonly used materials are HDPE
and PP. PC is also used as sheets for some
special applications. Following are the
advantages and disadvantages of plastic
corrugated boards, which designer should
keep in mind while selecting the material.
Table 4.1. Advantages and
disadvantages of plastic
corrugated boxes
Fig.14.9. HDPE crates.
There are five different methods employed
to manufacture plastic crates: Injection
moulding; Compression moulding; Blow
moulding; Rotational moulding; and
Thermoforming. Each process is suited to
the production of a range of geometries with
a variety of materials at different costs. But
the most often used method is injection
PLASTICS IN FOOD PACKAGING
Advantages
Disadvantages
Long life
Cost
Chemical resistance
Insulation
Formability
Temperature
resistance
Multiple colour
choice
UV degradation
Strength:weight ratio
Waterproofness
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Forming Methods
Corrugated plastic boards are
manufactured using standard box making
techniques. Generally, flatbed presses using
cam action or single stroke are used to diecut, score, crease, or fold the material. Threepoint or four-point, single-side bevel-edge
rule is used for cutting. Six-point creasing is
used for creasing parallel with the flutes,
three-point of creasing across the flutes, to
obtain a 90° bend. The polyolefin board has
a “memory” and, unlike paperboard, will
generally attempt to return to its previous
shape. This characteristic calls for modified
bending and creasing techniques.
High-frequency welding is the method
used for joining the material. Because of the
nature of the polymer, glues are not generally
successful. But lap joints have been
accomplished using corona-treated board
with silicone-type or hot melt adhesives.
Metal stitching can be used, but this creates
a weak spot immediately surrounding the
staple.
Chapter 4
Pallets
Plastic pallets are primarily used inside
the plants or in closed-loop shipping system
due to their higher costs. Plastic pallets are
almost always found in applications where
the user can retrieve most of the pallets after
each trip. Following are the advantages of
plastic pallets:
l
Long pallet life
l
Reduced load damage
l
Easy cleanup
l
Reduced worker injury
l
Chemically inert
l
Moisture proof
l
No harbor for pests
l
Nestability
l
Interstackability
The commonly used materials are HDPE,
PS and FRP. But HDPE is the most favoured
material because of low cost, uniform
performance, ready availability, wide
acceptance, excellent resistance to impact,
and good performance under wide range of
operating conditions. The only negative
point of HDPE is the poor creep resistance.
Following are the methods employed for the
manufacture of plastic pallets:
l
Structural foam moulding
l
Injection moulding
l
Rotational moulding
l
Thermoforming
l
Reaction injection moulding
Foams
Fig. 4. 20. HDPE and PP corrugated sheets.
The mould comprises of two walls
between which steam is diffused through a
mass of plastic granules (EPS, PE,
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
polyurethane), entering by a large number of
apertures or slitted plates uniformly
distributed over the inner wall.
Expanded Polystyrene Foaming
Conversion is carried out by raising the
temperature in two stages. In the first stage,
pre-expansion or free expansion of
polystyrene beads yields expanded
polystyrene flakes. These flakes are then
used to fill the mould, and they expand to
take the form of the mould under heat and
pressure. Two processes exit: heating by hot
air followed by compression, and steam
heating of the mould. Blocks and moulded
shapes may be produced.
Polyurethane Foaming
Conversion starts with dosing machines
that feed the basic liquid ingredients to a
mixing head which deposits them on the belt
(free foaming) or into a closed mould (forced
foaming) where expansion begins. There are
two kinds of machines: the low pressure
“pre-polymer” machine (in which mixing is
by agitator of compressed air and feeding by
gear pump) and high pressure “one-shot”
machine.
Polyethylene Foaming
Conversion starts with a mixture of
polymer and blowing agent to which
crosslinking agents (peroxides of dicumulated butyl and tributyl) are added.
Shaping is effected by calendaring. Chemical
or radiation crosslinking is accomplished at
temperatures below the breakdown
temperatures of the blowing agent.
CLOSURES
Screw Caps
Screw caps are generally injection
moulded from wide variety of plastics such
PLASTICS IN FOOD PACKAGING
89
as
polyethylene, polystyrene or
polypropylene or compression moulded
from phenol-formaldehyde and ureaformaldehyde. They are commonly used on
plastic bottles or jars.
Polypropylene caps are particularly
valuable as closures for cosmetic
preparations because of their design
possibilities. Polypropylene has good
resilience so that mouldings having slight
undercuts can be “jumped-off” the mould
core without damage to the moulding.
Decorative inserts can be pressed into these
moulded-in undercuts to give caps with
highly effective sales appeal. The resilience
of polypropylene also makes possible the
design of linerless closures.
Plug Fitting
This type of closure is normally injection
moulded from low-density polyethylene
since its softness and flexibility enables it to
give a good seal, even against hard, smooth
surfaces such as walls of polystyrene tube.
The plug itself is often ribbed to give even
better sealing.
An interesting example of the design
possibilities inherent in the use of plastic is
the plug closure which incorporates flexible
prongs on the underside of the plug. The use
of this closure for tablet tubes eliminates the
necessity for a wad of cotton wool on top of
the tablet to prevent their movement with
consequent risk of breakage during transport.
Again no special equipment is necessary for
closing.
Push-on Covers
This type of closure is the normal one for
injection-moulded plastic pots or jars and
for some types of vacuum-formed containers.
In addition to plastic push-on covers,
90
Chapter 4
paperboard ones are still used in some
instances. Before applying the push-on
cover, a foil diaphragm is often crimped over
the top of the pot or jar. This gives extra
protection or a tamper-proof seal.
In
thickness gauges, aluminium foil is
sometimes used as the only closure, as in the
case of yoghurt containers. Flexible pushon covers (in low density polyethylene) can
also be used for bottles.
Heat-sealed Covers
These are often used for closing vacuumformed containers of the tray type, or the
deep drawn pyramid type used for fruit
drinks. The cover may be flat or recessed to
give a shallow plug-type fitting to the
container with a consequent increase in
rigidity and strength. Sealing is carried out
with a heated jig. With certain types of
equipment it is possible to vacuum form
plastics sheet continuously from the reel, fill
the depressions so formed, then covers them
with another plastic sheet fed from a separate
reel. After heat sealing, the cover on the
containers are cut out and trimmed.
Miscellaneous Closures
The possibilities for design inherent in
moulding of plastics have led to many special
types of closures, such as combined plug
and snap-on covers and plug or screw-caps
which incorporate means of dispensing the
contents in droplet form or as a jet or spray.
Such closures are usually fitted to “squeeze”
bottle designs. Another interesting design
feature which is often incorporated in plastic
closures is the integral moulding of a nozzle
and cap to give a captive closure. The
assembly is fitted as a plug in the bottle neck.
The same result has also been achieved by
the use of a snap-on action retaining ring.
Fig. 4.21. Closures.
SPECIALITY PACKAGING
Vacuum and Gas Packaging
Where foods are susceptible to oxygen,
as frequently occurs in the presence of light,
it is helpful to exclude air from the package.
Vacuum packaging is more a means of
keeping a food at better level of quality during
Table 4.2. Some examples of
gas-flushed packaging at
refrigerated temperatures
Food
Gases
Shelf-life
(days)
Red
meats
70% Oxygen
30% Carbon dioxide
7
Organ
meats
40% Carbon dioxide
50-60% Oxygen
6-10
Processed 20-50% Carbon dioxide
meats
50-80% Nitrogen
21
Fish
Pizzas
80% Carbon dioxide
20% Oxygen
4-8
50% Carbon dioxide
505 Nitrogen
21
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
91
Table 4.3. Gases used in packaging and their applications
Gases
Applications
Nitrogen
As a pressure-relief agent to prevent external atmosphere from crushing the
product. Nitrogen is inert gas. It does not react with foodstuffs. Common
packaging applications: bulk-pack bacon and sauces, shredded and sliced
cheese and beef jerky, snack foods.
Carbon
dioxide
Depending upon applications, 20-100% carbon dioxide may be used.
Carbon dioxide lowers the pH of the food and can exert a powerful slowing
effect on the growth of microorganisms. Primary application is for baked
foods, cookies, cakes, breads, dough and pasta products. Carbon dioxide
tends to be absorbed into the actual body of the food product itself. Carbon
dioxide is frequently mixed with nitrogen to prevent the package from
clinging too tightly to the product. On the other hand, some products which
are not sensitive to strong pressure or tight cling, but which are susceptible
to spoilage by mould growth, are packaged in an atmosphere of 100%
carbon dioxide.
Oxygen
The applications using oxygen are primarily for red meat. The concept is
widely used in Europe for centrally packaged retail cuts. Oxygen is used
as an oxygenating agent at levels in the range of 40-80% to form the bright
red meat colour. When oxygen is used, it is usually mixed with carbon
dioxide and nitrogen—carbon dioxide for its preservation effect, nitrogen
to provide a bulking agent. Oxygen tends to disappear inside the package.
It can be metabolized by the meat to carbon dioxide which is absorbed in
the water phase of the meat as carbonic acid.
its natural life than a means of increasing its
shelf life. Under good vacuum conditions,
the oxygen level is reduced to less than 1%.
In the case of vacuum packed meats,
Fig. 4.22. Nitrogen filled snack
food packages.
PLASTICS IN FOOD PACKAGING
respiration of the meat quickly consumes the
residual oxygen replacing it with carbon
dioxide which eventually increases to 1025% within the package.
Packaging material required for vacuum
packaging must possess high resistance to
gas permeability and water vapour
transmission with perfect seals and also
should have good mechanical strength.
Typical materials used are: 1. K-Nylon/
LLDPE, MXXT/LLDPE, K-PET/LLDPE 2.
Laminates of plastic films with aluminium
foil. Food products like bacon slices, ham,
fish, cheese, coffee, tea, meat, etc. are vacuum
packed.
92
In gas flush packaging the gases used
and their applications are given in Table 4.2
and 4.3.
Retort Packaging
Pouches
The materials used in making retort
pouches should possess toughness and
puncture resistance normally required of
flexible packaging, good barrier properties
for long shelf-life, and heat sealability over a
wide temperature range along with the ability
to survive retort temperatures. To get all
these desired properties in the pouch material,
laminate structures or coextruded films are
used.
The outer film of the composite structure
is needed for strength and flex resistance. It
should be resistant to heat-seal temperatures,
printable, and be able to withstand retort
temperatures without bursting, shrinking
and delamination. The present material of
choice is polyethylene terephthalate (PET).
It has the added advantage of being reverse
printed so that ink is embedded between the
outer layer and the next inner layer.
In order to achieve a shelf-life of one year
or more, aluminium foil layer as one of the
inner layers for barrier properties is essential.
The thickness range of aluminium foil varies
from 9 to 25µm though 9 µm thickness
currently predominates. Thicker foils tend
to result in more flexure failures and form
more permanent creases or peaks that act as
loci for abrasion failures. In Japan, non-foil
pouches are quite common since a much
shorter shelf life of 3-6 months is acceptable.
Nylon is another material used as a barrier
film in place of aluminium foil because of its
low gas transmission rate and toughness.
Being transparent, nylon based laminates
cannot provide protection from light unless
Chapter 4
covered with a overcarton or wrap. The other
transparent materials used in place of
aluminium foil are EVOH, PVDC, aluminium
oxide and silicon oxide coatings on PET.
The current material of choice for inner
sealant layer is cast polypropylene, though
high density polyethylene modified with
isobutylene rubber is also used.
Since thermoprocessing imposes higher
performance criteria on pouch materials,
developmental efforts centred around the
formulation of adhesives and primers
capable of laminating the dissimilar plies
together with adequate strength to withstand
all the rigours of heat sealing, retorting and
distribution handling, while being
acceptable to regulatory agencies from the
standpoint of not contributing harmful
components to the foods. Quality assurance
procedures are strictly adhered to in view of
the several critical factors involved in pouch
performance.
Semi-rigid Containers
Retortable semi-rigid containers are of
tray or tub type with a structural supporting
body and a sealable flexible lid. The tray
package is a thin-profile package that offers
all the advantages of the retortable pouch
with the added convenience of a serving
dish. Improved techniques of thermoforming or cold impact forming and
coextrusion have recently advanced the
state-of-art of this package. Thermoforming
is relatively low-cost technique, wherein the
sheet is heated to an optimum temperature
and it is then forced into a female cavity
mould by compressed air, vacuum, or a male
die.
Advantages of semi-rigid packages
include ease of filling or top-loading of
products with or without in-line forming of
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
the container, and potential increases in line
speeds due to multiple pocket forming on a
wide web-style operation.
Original semi-rigid packages were made
of aluminium foil laminates with cast
polypropylene as sealant layer. Oriented
polypropylene was used as exterior layer.
The 80’s have seen high barrier plastics
coming into use to serve as an effective
replacement for aluminium in order to make
the containers microovenable. Two resins
that are being used in these are
polyvinlyledene chloride (PVDC or saran)
and ethylene vinyl alcohol copolymer
(EVOH or EVAL).
Though these resins are prohibitively
expensive, multi co-extrusion permits the
burying of a thin layer of the barrier layer
between two or more thicker layers of less
expensive polymer. While PVDC provides
an excellent barrier to oxygen, its resistance
to re-melting and hence the inability of using
its regrind may prove to be a disadvantage.
In case of EVOH, the barrier to oxygen
transmission is adversely affected in presence
of high humidity. The use of a desiccant in
the tie layers to capture any errant moisture
is believed to solve this problem.
In the rotary thermoforming process, a
multi-layer sheeting is directly coextruded
on to a rotary drum, where it is thermoformed
into multicavities while it is still above the
melt temperature of the polyethylene. The
higher temperature is expected to result in
stress-free containers, thereby minimizing
warping during retorting.
Following are the typical laminate
structures used for retort pouches and trays:
PLASTICS IN FOOD PACKAGING
93
Pouches
CPP
PET/CPP
CPP/Nylon/CPP
PET/Al.foil/CPP
PET/Al.foil/Nylon/CPP
PET/SiO2 on PET/CPP
PET/Al2O3 on PET/CPP
PET/PVDC on PET/CPP
PET/EVOH/CPP
Trays
CPP
PET/CPP
PET/Regrind/PVDC on PET/CPP
PET/Regrind/EVOH/CPP
CPP/Regrind/EVOH/Regrind/CPP
Fig. 4.23. Retortable pouches and trays.
Aseptic Packaging
Aseptic processing and packaging
basically consists of filling of the
commercially sterilized product into
presterilized package under aseptic
conditions and sealing with a presterilized
closure in an atmosphere free of
microorganisms. Aseptic packaging consists
of the following steps:
94
l Heating the product to sterilization
temperature and holding it at that
temperature to achieve commercial
sterility,
l Cooling of the product,
l Filling into sterile containers in sterile
atmosphere and sealing aseptically.
The versatility of aseptic technology has
given rise to the use of a variety of plastic and
polyolefin materials for packaging. Since
aseptic applications require both product
preservation, and utility from the packages,
there are several basic requirements that
these relatively new packaging materials
must meet for successful application in the
marketplace, and the most of them are
product-or usage-dependent.
Chapter 4
through the package as required by the
product.
The package forms that are used in aseptic
packaging are: Rectangular and tetrahedron
shaped cartons, Cups, Bags, bottles and bag
in box/drums. The packaging materials are
sterilized by using either H2O2 in combination with heat or gamma irradiation.
The typical packaging structures used
are:
LDPE/Paperboard/PE/Al.foil/PE/
LDPE/ LLDPE.
LLDPE/EVOH/LLDPE
PET/Al.foil/Paperboard/PP or PE
1. The packaging materials must be
acceptable for use in contact with the
intended product, and must comply with
material migration requirements
applicable.
2. Physical integrity of the package is
necessary to assure containment of the
product and maintenance of sterility. The
term integrity applies to the structural
integrity of the container itself as well as
that of the closures and seals to assure
package soundness and hermeticity
during handling and distribution.
3. The package material must be able to be
sterilized and be compatible with the
method of sterilization used (heat,
chemical or radiation).
4. The package must provide the barrier
protection necessary to maintain product
quality until it is used. Barrier protection
means control over the transmission of
oxygen, moisture, light, and aroma
Fig. 4.24. Aseptic consumer packs
and bulk bags.
Frozen Food and Oven-Proof Trays
The continuing growth of microwave
oven sales and increasing consumer use of
microwave ovens for cooking processes as
well as other conventional ovens has made
development of dual-oven-proof trays an
important proposition in packaging. One of
the largest markets for microwave ovenproof trays is restaurants equipped with
microwave ovens for quick service. Most
plastic trays and paperboard trays with
grease-proof coatings are available for
microwave oven use only, since temperatures
to which trays are exposed are lower than
100°C(boiling point of water).
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
Social trends and changing life styles,
that have made dual-oven-proof paperboard
trays dominant in the market, include:
1. Growing popularity of convenience
foods,
2. Increasing institutional catering,
3. Development of the microwave oven,
4. Development of dual-oven-proof PETcoated paperboard,
5. The higher production cost of metal and
plastic containers,
6. Energy factors,
7. Environmental factors.
Requirements for Dual-Oven-Proof
Trays
The Primary requirements of dual-ovenproof tray for food packaging are as follows:
1. Protect the food contained,
2. Aesthetic appeal to the user,
3. Ease of heating or cooking the food for
serving,
4. Operating efficiency in manufacturing,
and
5. Cost efficiency.
Each requirement must be satisfied by the
physicochemical functionalities or
properties of materials used in the tray
manufacture.
Requirements for Dual-Oven-Proof
Paperboard
Dual–oven-proof paperboard has been
developed primarily in conformity with the
requirements for dual-oven-proof trays
already described. Detailed requirements or
PLASTICS IN FOOD PACKAGING
95
advantages of dual-oven-proof paperboard
for oven-proof trays are as follows :
1. Dual-oven-proof quality : Paper itself
has a high heat resistance, which is
reinforced by the PET coatings. An oven
temperature in cooking could be as high
as 240°C, and heat resistance against
200-220°C for 30 min is sufficient for most
applications.
2. High temperature resistance : Ovenproof trays used for frozen food
packaging must have a high heat
resistance, going from deep freezing at –
40°C to reheating at 200-220°C for 30 min.
3. Browning and odor development
resistance : Browning of paperboard is a
major problem to be overcome with PET
coating on paperboard as a material of
dual-oven-proof trays.
Heat is
accumulated along the tray flange, while
the walls are protected from rising
temperature by the heat-sink effect from
the foods contained. Coatings should
not be degraded to generate odor at oven
temperatures.
4. Good performance under deep freeze
conditions : Frozen foods are handled
and distributed under deep-frozen
conditions at lower than –15°C, typically
–40°C. Oven-proof trays must have
sufficient properties as packaging for
frozen foods at that temperature.
5. Grease and water resistance : These are
other important roles of coating, and also
are primary requirements for a packaging
of frozen foods that will be used to heat
and serve.
6. High in productivity : This refers to not
only productivity of tray itself but also
productivity at the packaging operation,
96
Chapter 4
Table 4.4. Dual-oven-proof trays
Basic Material
Coating
Forming
Paperboard (pulp)
PET
Acrylic
Silicone
Polybutylene terephthalate (PBT)
Pressed forming
Folded forming
Molded forming
Plastic (PET)
-
Vacuum forming
Molding (thermoset)
Aluminium
Plastics
Pressed forming
Drawn forming
which are very important in the cost
performance.
7. Printability : Ease of printing and aesthetic
qualities are distinctive properties of
paperboard.
8. Heat sealability and gluability : These
are primary requirements for food
packaging to protect the contents. Coating
affects these requirements strongly,
especially heat sealability, which is not
original property of paperboard.
9. Heat tolerance in physical properties : A
tray with food, reheated for serving, must
have sufficient physical properties for
holding food and serving on the table
without any troubles. Rigidity and grease
and water resistance are important
properties.
10. Safety as food packaging materials : All
the materials used should be in
conformity with regulatory requirements
and be approved.
11. Microwave safe : Molecules often
generate heat from electric oscillation of
microwaves which may result in their
degradation and hazardous substances.
PET Tray
Dual-oven-proof PET trays have been
developed for more than 10 years, and a few
products have been introduced. PET has
appropriate properties as a material for dual
oven-proof trays, including cost of resin,
heat resistance, mechanical properties, ease
of processability, and compatibility with
food products as well as availability of an
amorphous and a crystalline state. PET can
be extruded to sheeting and can be
thermoformed at its amorphous state, and
high heat resistance can be achieved in the
crystalline state, which is the primary
property of the tray for conventional oven
use.
Modified Atmosphere Packaging
(MAP)
It is a food preservation technique, in
which the composition of atmosphere
surrounding the food is changed from the
normal composition of air. Unlike controlled
atmosphere storage, in MAP, there is no way
of controlling the atmosphere components
at specific concentrations once a package
has been hermetically sealed. There are two
different methods of MAP: Active
modification and Passive modification.
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
97
packaging that performs a role other than an
inert barrier to the external environment.
The active functions can be achieved by
any one of the methods given below:
1. Scavenging undesirable substances,
2. Release of active substances,
3. Using other new functional package
designs/materials.
Fig. 4.25. Packaging for frozen foods.
The typical packaging forms used in
MAP are pillow pouches, bag-in-boxes and
trays with overwrapping. MAP has wide
applications in the area of fresh fruits and
vegetables and in meat preservation.
The packaging materials used are as
follows:
Pouches
PET/PVDC/LDPE/LLDPE
PA/PVDC/LDPE/LLDPE
PC/EVOH/EVA
MPET
MOPP
OPP/PVDC
Trays
UPVC/LDPE
Oxygen present in the headspace in food
package results in oxidation and
development of moulds, fungi and bacteria,
resulting in spoilage of food. The oxygen
can be removed from the package by using
the following types of oxygen scavengers:
1. Iron-based,
2. Metal/acid-based,
3. Metal (e.g. platinum) catalyst based,
4. Ascorbate/metallic salts based,
5. Enzyme-based.
Ageless® is a very popular sachet type
oxygen scavenging system being used world
over. Similarly ethylene scavengers and
antimicrobial agents are also incorporated
in films to perform specific functions to
increase the shelf life of the commodities.
Smart packaging is an advanced active
packaging system that contains additional
HDPE
EPS/EVOH/LDPE
Bag-In-Box
PA/LDPE
PA/EVOH/LDPE
Active and Smart Packaging
Active packaging can be defined as
PLASTICS IN FOOD PACKAGING
Fig. 4.26. Baby corns and ladies fingers in
PS tray wrapped with transparent films.
98
Chapter 4
Table 4.5. Common plastic materials and forms and their
applications in food industries.
Types of Plastics
Applications
Low density polyethylene
Foods, milk, frozen foods, agricultural products, shrink
wrapping, heavy duty sacks, coating, lamination, multilayer composites, coextrusion, containers and liners.
Linear low density
polyethylene
Trash bags, ice bags, produce bags, shrink, aseptic
bags films, heavy duty shipping sacks, liquid milk
packs, edible oil packs and lamination film, etc.
High density polyethylene
Woven sacks, films, drums, barrels, milk can bottle
crates, fish crates, transport containers, pallets, moulded
containers, bags, tapes, strips, blown films, extrusion
coating, corrugated sheets, etc.
Films, rolls, bags, pouches, drum liners, garbage bags,
lamination for fertilizer packages, milled wheat
products, wrapping films, etc.
Woven sacks, strappings, films and laminates, pouches.
Packages for textiles, apparels, bakery products (biscuits,
bread, cakes etc.), metallized films, shrink films closures,
corrugated sheets, blown moulded bottles, extrusion
and stretch blow moulded items, heavy crates, boxes,
bucket containers, extruded nets, knitted sacks,
corrugated boxes, etc.
High molecular high
density polyethylene
Polypropylene
Expanded polypropylene
Insulation, packaging medium for electrical and
electronics items as a cushioning material, wrapping,
liner, etc.
Polyvinyl chloride
Films, sheets, bags, liners, shrink films, shrinkable tubes,
skin/blister packs, laminates, adhesive tapes, bottles,
etc
Nylon-6
Oxygen and odour sensitive foods, edible oils, spices
Polyester
Spices, instant foods, bakery and confectionery, bottles,
laminates etc.
Polyurethane
Coatings, foams, sheets, etc.
Polystyrene
Thermoformed containers for ice cream, condiments,
jam, etc.
Expanded polystyrene
Insulating and cushioning material, beverages, frozen
foods, fans, motors, typewriters, computers, electricals
and electronics, etc.
PLASTICS IN FOOD PACKAGING
PLASTICS BASED PACKAGE FORMS &
SPECIALITY PACKAGING FOR FOOD PRODUCTS
99
functions beyond barrier and protecting
functions. It also exhibits sensing and
interactive and responsive mechanisms. The
function of smart packaging are:
Jenkins WA and Harrington JP (1991).
Packaging Foods with Plastics. Technomic Publication, Lancaster, Pennsylvania.
l To improve product quality and product
value,
Paine FA (1962). Fundamentals of Packaging. John Wiley and Sons, London.
l To provide more convenience,
Paine FA (1977). Packaging Media. John
Wiley & Sons, London.
l To change gas permeability,
l To provide protection against theft,
counterfeiting and tampering.
There are different techniques used in
smart packaging: Time temperature
technique; Oxygen indicators; Microbial
growth indicators; Moisture indicators, etc.
BIBLIOGRAPHY
Paine FA and Paine HY (1983). Handbook
of Food Packaging. Leonard Hill,
Glasgow, UK.
Parry RT (1993). Principles and Applications of MAP of Foods.
Peleg K (1985). Produce Handling, Packaging and Distribution. AVI Publications, West Port, Connecticut.
Athalye AS (1992). Plastics in Packaging.
Tata McGraw Hill, New Delhi.
Robertson GL (1993). Food Packaging:
Principles and Practice. Marcell Decker,
New York.
Brody A (1997). The Encyclopedia of
Packaging Technology. John Wiley and
Sons, USA
Sacharow S and Griffin RG (1980). Principles of Food Packaging. AVI Publications, West Port, Connecticut.
Brown WE (1992). Plastics in Food
Packaging. Marcel Dekker Inc, New York.
Sathish HS (1996). Profile on Food
Packaging. CFTRI, Mysore.
PLASTICS IN FOOD PACKAGING
100
Chapter 4
PLASTICS IN FOOD PACKAGING
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