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Metal packaging material
1. METAL PACKAGING MATERIAL
FST-505 FOOD PACKAGING
Submitted to: Er. D. S. Bunkar Sir
Submitted By: Jagriti Bhasin
ID: 19412FST008
M.Sc. 1st year
Department of Dairy Science and Food Technology
Banaras Hindu University
3. Introduction
• Metal packaging plays an important role in the process of food preservation.
• The common expression used to describe such a process is "canning". Canned food
has become an important part of the human diet in developed countries during the
past century.
• Metal packaging has a double function as a protection against any external influence
on the foodstuff during heat treatment and storage and as a sales and information
pack.
• The basic requirement for such a package is the hermetic tightness of the container.
• Two basic types of alloyed metals are used in food packaging i.e. steel and aluminum.
Steel is used primarily to make rigid cans, whereas aluminum is used to make cans
as well as thin aluminum foils and coatings.
• Nearly all steel used for cans was coated with a thin layer of tin to inhibit corrosion,
and called as “tin can”.
4. STEEL
• Steel grades for food contact packaging applications are essentially electrolytic tinplate
(ETP) and electrolytic chromium/chromium oxide coated steel (ECCS).
• Electrolytic tinplate (ETP) is a cold-rolled low carbon mild steel sheet or coil coated on
both surfaces with tin that is applied in a continuous electrolytic operation.
• Tinplate can be differentially coated when one of its surfaces carries a heavier tin
coating than the other. Usual coating weights range from 1 to 15.1 g/m2.
• The most common alternative to electrolytic tinplate for food contact applications is
ECCS (electrolytic chromium/chromium oxide coated steel), which has equal coating
weights on both surfaces of the coil.
• The function of a chromium coating is to prevent atmospheric oxidation or sulphur
staining of the steel by foodstuffs and to improve lacquer adhesion.
• ECCS is always used with an additional organic coating (i.e. can coating). It is normally
used for the manufacture of drawn cans, can ends.
5. ALUMINIUM
• Aluminium is widely used in food contact materials. Aluminium
alloys used for food contact may contain elements such as
magnesium, silicon, iron, manganese, copper and zinc.
• Aluminium and its various alloys are highly resistant to
corrosion. When exposed to air, the metal develops a thin film
of aluminium oxide (Al2 03 ). The film is colourless, tough and
non-flaking and few chemicals are able to dissolve it.
• Aluminum has considerably less structural strength than steel
at the same gauge thickness. This means that aluminum has
limited use in cans such as those used with retorted foods.
• Aluminum works well in very thin beverages cans that contain
internal pressure such as soda or beer. This internal pressure
from CO2 gives rigidity to the can.
6. RECYCLING OF PACKAGING METAL
• Both aluminum- and steel-based packaging materials are readily
re-melted by the metal manufacturers.
• Waste materials arising during the can-making processes may be
returned for recycling through third party merchants.
• Postconsumer metal packaging waste is collected and, after
automatic separation from other waste materials, is ultimately
returned to the metal manufacturers for re-melting.
• Aluminum and steel suffer no loss of quality during the re-melting
process so may be reused an unlimited number of times for the
production of first-quality packaging material.
• Certain recycling processes permit the tin to be separated from
the steel base prior to re-melting.
7. MANUFACTURING OF TIN
TINPLATE :
• Tinplate is the most common metal material used for food cans. It consists of a low-
carbon, mild steel sheet or strip, 0.50–0.15 mm thick, coated on both sides with a layer
of tin. This coating seldom exceeds 1% of the total thickness of the tinplate.
• The combination of tin and steel produces a material that has good strength, combined
with excellent fabrication qualities such as ductility and drawability as well as good
weldability, nontoxicity, lubricity, lacquerability and a corrosion-resistant surface of bright
appearance.
Structure of tinplate :
8. • The mechanical strength and fabrication characteristics of tinplate depend on the
type of steel and its thickness.
• The hardness of steel is a very important attribute in manufacturing of various
packaging material, it is measured using Rockwell Hardness test.
• The Rockwell hardness test has been adopted as the industry standard to express
temper because of its simplicity and overall good correlation with fabrication
requirements.
• Typical temper values for blackplate and ETP(electrolytic tinplate) are presented in
Table 1.
• The minor constituents of steel are carbon, manganese, phosphorous, silicon,
sulphur and copper. At least four types of steel, with different levels of these
constituents, are used for food cans. The corrosion resistance and appearance of
tinplate depend on the tin coating.
• The four main grades of steel product for subsequent use in tinplate production are
shown in Table 2.
11. TINPLATING
Cleaning (Is done in
Pickling and
Degreasing unit)
Washing (to prepare
substrate for plating)
Electroplating ( either
by Acid stannous
sulfate process or by
halogen process)
Coating(Flow Melting)
Rapid quenching in
water
Electrolytic treatment
in Sodium dichromate
electrolyte
Passivation
Oiling(Light oiling)
Strips are shreared
into sheets or coiled.
Packaged for shipment
to the Can
Manufacturer
12. TIN COATING:
• The role of tin coating is an essential component of the can
construction and plays an active role in determining shelf
life.
• The most significant aspect of the role of the tin coating is
that it protects the steel base-plate which is the structural
component of the can.
• Without a coating of tin, the exposed iron would be
attacked by the product and this would cause serious
discoloration and off-flavors in the product and swelling of
the cans; in extreme cases the iron could be perforated
and the cans would lose their integrity.
• The second role of tin is that it provides a chemically
reducing environment, any oxygen in the can at the time of
sealing being rapidly consumed by the dissolution of tin.
This minimizes product oxidation and prevents colour loss
and flavor loss in certain products.
13. MANFACTURING OF ECCS
ELECTROLYTIC CHROMIUM-COATED STEEL (ECCS):
Electrolytic chromium-coated steel (ECCS), sometimes described as Tin free steel, is
finding increasing use for food cans. It consists of low-carbon, mild CR or DR steel
coated on both sides with a layer of metallic chromium and chromium sesqueoxide,
applied electrolytically. ECCS is less resistant to corrosion than tinplate and is normally
lacquered on both sides. It is more resistant to weak acids and sulphur staining than
tinplate.
Structure of ECCS plate:
14. MANUFACTURING OF ALUMINIUM
Aluminum is used in the form of foil or rigid metal.
Aluminum Foil
• Aluminum foil is produced from aluminum ingots by a series of rolling operations
down to a thickness in the range 0.15–0.008 mm.
• Most foil used in packaging contains not less than 99.0% aluminum, with traces of
silicon, iron, copper and in some cases, chromium and zinc.
• Foil used in semi rigid containers also contains up to 1.5% manganese. After
rolling, foil is annealed in an oven to control its ductility. This enables foils of
different tempers to be produced from fully annealed (dead folding) to hard, rigid
material.
15. • Foil is a bright, attractive material, tasteless, odorless
and inert with respect to most food materials. For
contact with acid or salty products, it is coated with
nitrocellulose or some polymer material. It is
mechanically weak, easily punctured, torn or abraded.
• Foil is used as a component in laminates, together with
polymer materials and, in some cases, paper. These
laminates are formed into sachets or pillow packs on
FFS equipment .
• Examples of foods packaged in this way include dried
soups, sauce mixes, salad dressings and jams. Foil is
included in laminates used for retortable pouches and
rigid plastic containers for ready meals. It is also a
component in cartons for UHT milk and fruit juices.
16. ALUMINUM ALLOY
• Most commercial uses of aluminum require special properties that the pure metal
cannot provide. Therefore, alloying agents are added to impart strength, improve
formability characteristics and influence corrosion characteristics.
• A wide range of aluminum alloys is commercially available for packaging
applications, depending on the container design and fabrication method used. The
chemical composition and typical usage of some of the more commonly used
aluminum alloys (the aluminum is at least 99% pure) are shown in Table 3.
• Hard-temper aluminum alloy, containing 1.5–5.0% magnesium, is used in food can
manufacture. It is lighter but mechanically weaker than tinplate. It is manufactured in
a similar manner to aluminum foil.
• It is less resistant to corrosion than tinplate and needs to be lacquered for most
applications. A range of lacquers suitable for aluminum alloy is available, but the
surface of the metal needs to be treated to improve lacquer adhesion.
18. MANUFACTURING OF CANS
CAN MATERIALS: Cans are made from either
aluminium or steel. The steel can be chrome plated or
laminated. The commonly called tin can is a misnomer.
The sheet of these cans have only a thin coating of tin
either on one side or on both sides.
CAN CONFIGURATIONS: The three basic types of
cans are: three-piece cans, two-piece drawn and ironed
cans and two-piece drawn and redrawn cans.
19. THREE-PIECE CANS
• Three-piece cans are mainly used for food, but may be used for some
non-carbonated beverages, particularly fruit juices.
• They were the original cans, consisting of a bottom (end), walls
(body) and lid. They are made with ETP only being used for the body,
in order to facilitate welding, whilst TFS or ETP could be used for the
ends or possibly aluminium if an easy-open end (lid) is used.
• The components of the three-piece can are cut from steel after
coating (if used). The wall of the can is rolled to form a cylinder and
the seam (joint) is welded. A protective lacquer is then applied to this
seam. It can be either liquid or powder and is known as a side seam
stripe. A bottom (either a classic or easy open end) is then attached.
After filling, a lid (classic end) is attached to close the can. Both the
bottom end and the lid have a gasket applied to ensure a hermetic
seal.
23. • Within three-piece category cans, there are further four
classifications determined by the method used to join
the side seam of the body cylinder. The methods are
soldering, welding , cementing and double seaming.
(i) Soldered seams: For soldered cans, the edges
of the blanks are bent, brushed with flux, passed over
a gas flame and joined in a lap and lock seam while
moving over a solder application seam, another
burner smoothens the seam and wiper removes
excess solder. The soldering seam is then treated
with a lacquer. The body blank is flanged to receive
the can bottom which is double seamed. The top of
the can is usually applied after a filling operation. In
the final step a spray coating is applied to the can
interior, cured and tested for leaks.
24. Fig.: Three-piece Can Welding Principles
(ii) Welded seams: The
welded side seams are very
strong and require a much
narrower undecorated strip than
that needed for soldering. In
welding, the side seam is an
overlap of the curled plate, which
is subjected to a high-amperage
electric current in a resistance
welding process. The resulting
exposed edge inside the can is
coated in a striping operation
using powder coating which is
cured by infra-red or high-
frequency induction heating.
25. (iii) Cemented seams: The cemented side seams permit all-round lithography with
no base strip required at the solder point. The body former curves the sheet to form a
cylinder and overlaps the edges. Cemented seams are produced by passing the body
blank edges over an open flame and applying special cement with wheel.
Chilling rolls then solidify the cement and trimming knives remove cement between
adjacent body blanks. The exposed edges are coated with lacquer. A thorough test is
to be followed before the cemented side seams are used for cans under pressure.
(iv) Double Seaming: After the side seam has been welded, the bodies are
transferred to a flanger for the final metal forming operation: necking and flanging for
beverage cans, and beading and flanging for food cans. The can rim is flanged
outward to enable ends to be seamed on.
The top of beverage cans is necked to reduce the overall diameter across the
seamed end to below that of the can body wall, yielding savings in the cost of metal
through the use of smaller diameter ends. This allows more effective packing and
stacking methods to be adopted, and prevents damage to the seams from rubbing
against each other. Simultaneous creation of the neck and flange using a spin
process is used. Double-, triple- and quadruple-neckings are now quite common, the
latter reducing the end diameter from 68 to 54 mm for the common beverage can.
26. Fig: Double Seaming of metal ends on to a metal container : (a) end and body are brought
together, (b) first seaming operation, (c) second seaming operation , (d) section through final
seam.
27. CAN SEAMER
• A Can seamer is a machine used to seal the lid (End) to
the can body such as in paint or food cans. The lid (End)
should be of metal while the body can be of metal
(beverage, soup, etc.), paper or plastic.
• Seam formed is generally leak-proof but this depends on
the product being canned. The seam is made by
mechanically overlapping the two layers to form a hook.
Different parameters of the hook are measured and
monitored to check the integrity of the seam under
different conditions.
28. TWO-PIECE CANS
These cans were developed in 1960's. This method of can
manufacturing eradicates the side seam and separate bottom.
The two-piece can body has an integral side and bottom and is
made in a process that thins the sidewall while maintaining the
thickness of the bottom. The widest use of these is in the beer
and soft drink markets.
Two-piece cans have technical, economic and aesthetic
advantages in comparison with soldered or welded three-piece
cans. In terms of integrity, the two-piece can has no side seam
and only one double seam, which is more easily formed and
controlled because of the absence of a side seam lap juncture.
There are two types of Two-piece cans : Draw and iron (D&I)
and Drawn and re-drawn Cans (DRD).
29. Two-piece Draw and Iron Cans: The drawn and wall-ironed can (DWI) is made
from a disc of metal 0.30–0.42 mm thick. DWI cans are mainly used for packaging
carbonated beverages. The internal pressure supports the thin wall.
Fig: Manufacturing of Draw and iron cans
30. Two-piece Drawn and re-drawn (DRD) Cans: These cans are used for
fruits, vegetables ,tuna and ready-meals.
Fig: Sequential stages in the production of DRD Cans: (1) Body
Blank , (2) Drawn Cups (3 &4) Diameter decreased, (5) Finished
trimmed can with profile.
31. END-MAKING PROCESS
1. Plain food can end and shells for food/drink easy-open ends:
The initial processes for making plain food can ends and easy-open ends for food
and drink cans are the same. The body of an end that will be ultimately converted
into an easy-open end is referred to as a shell. Plain ends/shells may be stamped
directly from wide coils of metal or from sheets cut from coils. Whether from coil or
sheet, the metal is fed through a press that produces multiple stampings for every
stroke.
After removal from the forming tool, the edges of the end shells are then curled
over slightly to aid in the final operation of mechanical seaming the end onto the
flange of the filled can. After curling, the end shells are passed through a lining
machine that applies a bead of liquid-lining compound around the inside of the
curl.
33. 2. Conversion of end shells into easy-open ends:
The principles used in the conversion of end shells are the same for both full aperture food
easy-open ends and small aperture drink easy-open ends. The conversion operations
comprise scoring (partially cutting through) the perimeter of the opening panel and
attaching a metal tab with which to tear-open the panel. Scoring is necessary to reduce the
force required to open the end to an acceptable level.
Fig: Easy open-end conversion
The pull-tab is made from a narrow
strip of pre-coated aluminum or steel,
which is in coil form. The strip is first
pierced and cut, and then the tab is
formed in two further stages before it
is ready to be joined to the end shell.
34. 3.Threaded Closures: Screw-top cans are containers with threaded closures. A
wide variety of threaded spouts and applicators have been available. A closure
could be specified by the size of the outside of the threads on the container.
There are no industry standards for threaded profiles, the caps from one
manufacturer may not fit containers from another. Caps and containers must be
purchased at the same time from the same source to ensure a good fit.
4.Slip Cover Closures: Shallow cans with slip covers are made by blanking and
drawing metal plate to the proper size and curling the edge. This category of
closures includes simple reclosure type; firm reclosure type or friction closure
type. There are still markets for highly decorated metal boxes, although the uses
of these slip cover containers have greatly decreased due to the labour intensive
cost of making these cans has soared and other types of mass-produced
containers have developed.
35. CAN LACQUERS
• Lacquer is a resin coating of cans which protect the
inside of the can from acids in food which would
otherwise attack the metal causing it to corrode.
• If the can is going to be stored in poor conditions
the outside of the can, can be lacquered as well, to
protect the metal from corrosion.
• The lacquering seals and protects the tin from
chemical reactions without affecting the food flavor,
it also prevents the dissolution of tins into the
products.
36. INTERNAL (FOOD CONTACT) COATINGS
• Protection of the contents from the metal - e.g. iron pick-
up in beer or discolouration or some dark-coloured fruits,
such as plums and strawberries, due to metal contact
• Protection from the contents of the can - e.g. acidic soft
drinks (which may corrode uncoated metal) or some fish,
meats and soups (which may cause sulphur staining).
37. EXTERNAL (NON-FOOD CONTACT) COATINGS
• Protection from the atmospheric corrosion
environment
• Support decoration, labeling and consumer
information
• Influence mobility of the article during filling
operations — e.g. beverage cans can only
be filled with an external decoration, which
provides the necessary friction (mobility) to
pass through the filling head.
External Additive Coating Machine
38. MAJOR CONSTITUENTS IN A CAN COATING
• Resin(s)
• Cross-linking agents (almost always present)
• Additives
• Solvents (not always present)
41. LACQUERING - METHOD OF APPLICATION
Lacquers can be applied in a following way
Electrophoretic Lacquers
Dip Applied Lacquers
Brush Lacquers
Spray Lacquers
Spray Lacquer Machine for Cans
42. APPLICATIONS
• BEVERAGES:
i) Carbonated beverages:- Two-piece Drawn and Iron(D&I) Cans.
ii) Non-carbonated beverages:- Three-piece Cans are mainly used for this
purpose.
• AEROSOL CANS: Few foodstuffs such as canned whipping cream are packed in
aerosol cans. Aerosol cans are either three-piece or two-piece.
• LIDS: Metal lids are used on glass jars and botte tops like in Jam jars and
Ketchup Bottles.
• DRUMS AND PAILS: These are made of three-piece cans. There are different
grades of drums depending upon the intended contents & method of
transportation. E.g.: Oils and other edible fats.
43. • FOOD CANS
Food cans are manufactured in a greater variety of sizes and shapes than
beverage cans.
Both three piece welded cans and two piece steel cans are commonly used. The
welding process produces a high-integrity three-piece can that is lead free.
Shallow drawn aluminium cans are used extensively for processed foods such as
vegetables, certain meat products, fillets of fish and various sauces.
Deeper cans drawn and ironed are used for vegetables in brine or sauces, soups.
Tomato sauce and mustard sauce are corrosive products, so the foods prepared
in them, if to be packed in aluminium can should not exceed total 3% acidity,
expressed as acetic acid.
Other fresh foods packed in D&R cans include meat, boned chicken, etc.
A few products like roasted coffee, milk powder are canned in dry state.
44. ADVANTAGES
• Total barrier to
Gas
Water vapor
Aroma
• Good compression resistance
• Good heat resistance
• Good thermal and physical shock
resistance
• Light protection
• Recyclable
DISADVANTAGES
• Metal is corrosive material, can affect
the quality of food.
• Metal is moderately heavy packaging
material.
• Can’t see the food content after
packaging
• Due to multi –step can manufacturing
process, can making is time taking
process.
• Metal can react with the food material.
45. CONCLUSION
• Competition among metal, glass and plastic packaging products will continue to be a
major force in overall container industry. Metal cans have been able to maintain a
large share of the market owing to technological advances permitting efficient high
speed operation and conservation of materials and energy.
• Recent innovations in the design and manufacture of metal packaging for food
products include: large opening stay-on-tab ends for drink cans, widgets to provide a
foam head to beer and chilled coffee, self-heating and self-chilling drink cans, full
aperture food can ends which are easier to open, square section processed food
cans for more efficient shelf storage, etc.
• The prime purpose of packaging in a metal container is the physical and chemical
protection of the product to be marketed. A perfect lacquered can is an ideal
container for food with respect to all these.
• This will ensure that metals will continue to have an extremely important part to play
in the cost efficient packaging of foods for short or long term ambient storage
conditions.
46. REFERENCES
• Food Packaging Principles and Practice; By: Gordon L. Robertson
• http://ecoursesonline.iasri.res.in/mod/page/view.php?id=1101
• http://ecoursesonline.iasri.res.in/course/view.php?id=28§ion=6
• http://ecoursesonline.iasri.res.in/mod/page/view.php?id=1099
• https://www.slideshare.net/SaptadeepSanyal/metal-packaging
• https://www.slideshare.net/keerthanapriya1/lacquering-keerthana
• http://epgp.inflibnet.ac.in/Home/ViewSubject?catid=15
