Materials for Canning and Bottling

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 : A lloy 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 material s . (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 White flint (clear glass) Colourless glass, known as white flint, is derived from soda, lime and silica. Pale green (half white) Where slightly less pure materials are used, the iron content (Fe2O3) rises and a pale green glass is produced. Dark green This colour is obtained by the addition of chromium oxide and iron oxide . 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 . 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 Safety: to be an inert material from a health and hygiene viewpoint 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 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.