Materials for Canning and Bottling of Food Products

1. COURSE NO: FET 427
Fruits and Vegetables
Processing Technology

2. Materials for Canning and Bottling
Mohammad Afzal Hossain
Assistant Professor
Dept. of Food Engineering and Tea Technology
SUST, Sylhet-3114

3. Containers for Canned Foods:
The container plays a vital role in food canning, it must be:
1) Capable of being hermetically sealed to prevent entry of
microorganisms.
2) Impermeable to liquids and gases, including water vapour
3) Maintain the state of biological stability (i.e, commercial
sterility) that was induced by the thermal process alone or in
combination with other chemical and physical processes.
4) Physically protect the contents against damage during
transportation, storage and distribution.

4. Can materials:
Wide varieties of materials are used now for manufacture of cans
for fruits and vegetables preservation. Yet metal containers
remain the most frequent used package for canning foods.
(a) Metal cans:
Alloy of iron with carbon and usually other elements
Tinplate, tin-free steel, and nickel-plated steel coated with a
very thin film of tin are the materials used to manufacture metal
food cans.
The amount of tin used being only about 1.5% of the can’s
weight and should not contain more than 1% lead. It is used to
prevent rusting.
Nausea, vomiting and diarrhea have been reported after
ingesting canned food containing 200 mg/kg of tin.

5. Can materials (contd.)
To prevent interaction between products and the metal,
cans are coated on the inside with an organic material.
Two general kinds of organic coatings are used in the food
industry : (i) acid-resistant and (ii) sulfur-resistant. Acid-
resistant coated cans are used primarily for fruit. Meat
products are generally packed in cans that have been lined
with sulfur-resistant materials.
(b) Aluminum/steel/tin
(c) Plastic
(d) Glass containers and metal closures

6. Although the wide variety of containers for canned
foods, the metal ones are preferable as:
1) It has a high conductivity of heat.
2) It cannot easily be broken.
3) Being opaque, so any possible bad effects of light on
food stuffs are avoided.
4) Be able to withstand the stresses imposed during
thermal processing and cooling.
5) Be able to withstand the subsequent handling, which
includes transportation, storage and distribution.

7. Use of metal packaging
Food is packed into a wide range of containers, some of
which consist of all metal whilst others have metal
components.
The different types of metal packaging include:
 Beer and soft drink cans
 Food cans
 Drums and pails
 Tubes
 Open trays
 Caps and closures (e.g. lids on glass jars and bottle tops)
 Lids (e.g. for yoghurt and butter containers).

8. METALS AND ALLOYS USED FOR FOOD
PACKAGING
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
 Highly resistant to corrosion
 When exposed to air, the metal develops a thin film of
aluminium oxide (Al2O3). The film is colourless, tough
and non-flaking and few chemicals are able to dissolve it
(Beliles, 1994).
 At neutral pH, aluminium hydroxide has limited
solubility

9. 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.
 At ETP, 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.

10. Tin
Tin can be applied as a thin layer on steel used for
metal packaging
Applied electrolytically during the manufacture of
ETP (electrolytic tinplate)
The tin layer provides corrosion resistance
If not coated tin can act as an efficient oxygen
scavenger
Use of uncoated tin is limited by the various possible
interactions between the metal surface and the
foodstuff and is therefore mainly used for, e.g. light
fruits in brine or tomato-based products.

11. Packaging of food in glass containers
Definition of Glass:
 The American Society for Testing Materials defined
glass as ‘an inorganic product of fusion which has
cooled to a rigid state without crystallizing’.
 Chemically, glass is made by cooling a heated, fused
mixture of silicates, lime and soda to the point of
fusion.
 Glass is hard and brittle, with a chonchoidal (shell-
like) fracture

12. Glass Types
1. White flint (clear glass)
Colourless glass, known as white flint, is derived from soda, lime
and silica.
2. Pale green (half white)
Where slightly less pure materials are used, the iron content
(Fe2O3) rises and a pale green glass is produced.
3. Dark green
This colour is obtained by the addition of chromium oxide and
iron oxide.
4. Amber (brown in various colour densities)
Usually obtained by melting a composition containing iron oxide
under strongly reduced conditions. Carbon is also added. Amber
glass has UV protection properties and could well be suited for use
with light-sensitive products.
5. Blue
Obtained by the addition of cobalt to a low-iron glass.

13. Attributes of food packaged in glass
containers
The glass package has a modern profile with distinct
advantages, including:
Quality image
Transparency
Surface texture
Colour
Decorative possibilities
Impermeability
Chemical integrity
Design potential

14. Attributes of food packaged in glass
containers(contd.)
Heat processable
Microwaveable
Tamper evident
Ease of opening
UV protection
Strength
Hygiene
Environmental benefits

15. Glass pack integrity and product
compatibility
I. Safety: to be an inert material from a health and
hygiene viewpoint
II. Product compatibility: enable liquid and solid
foods to be stored for long periods of time without
adverse effects on the quality or flavour of the product
III. Consumer acceptability:
 aesthetic appeal
 quality perception
 preferred taste
 product visibility and associated appetite appeal
 reseal ability.

16. Use of coatings for metal packaging
 Many metal packaging's (typically cans,
containers, caps and closures) are normally
coated on one or both sides. The inside (food
contact) coating is referred to as an internal
coating, lacquer or enamel and the outside
as external coating, enamel, ink or varnish.
Unlike many other applications, can
coatings are normally thermally processed
(stoved or baked).

17. Internal (food contact) coatings:
 Provide protection of the contents from the metal –
e.g. iron pick-up in beer or discolouration of some
dark-coloured fruits, such as plums and strawberries,
due to metal contact
 Provide protection of the metal can 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).

18. External (non-food contact) coatings:
 Provide protection of the metal from the
environment – e.g. atmospheric corrosion
 Support decoration, labelling and consumer
information
 Influence mobility (friction) 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.