Food Packaging & Storage Technology

Overview of World Market for Metal Cans

• The total world market for metal containers is estimated at 410 × 1012 units per annum, divided into:
• Drink cans: 320 × 1012 units
• Processed food cans: 75 × 1012 units
• Aerosol and general line cans: remainder

Container Performance Requirements

• Preserve and protect the product
• Resist chemical actions of the product
• Withstand handling and processing conditions
• Withstand external environment conditions
• Have correct dimensions
• Have required shelf display properties at the point of sale
• Give easy opening and simple/safe product removal
• Be constructed from recyclable raw materials

Container Design

• Shallow Tapered Wall Seamless:
• Types: round, non-round
• Economic concept: allows empty containers to be nested for minimizing transport costs
• Applications: fish
• Non-Round Cross Section:
• Structure: circular cans with lever lids and diaphragm seals
• Applications: powder products (infant formulas, instant coffee, dried milk)

Closure Systems

• Food cans:
• Require an aperture with either total or virtually full internal diameter of the container through which to remove the product
• Opening tools: can-opener to remove plain lid, full aperture easy-open ends (FAEOs)
• Drink cans:
• Aperture designed to suit method of consumption
• Closure systems: heat sealing mechanism, peelable membrane end

Raw Materials for Can Making

• Steel:
• Used in the form of low-carbon steel, converted into tinplate for manufacture of container and closure
• Tinplate manufactured by electrolytically coating blackplate with a thin layer of tin
• Advantages: provides good corrosion-resisting properties to steel
• Suitable for direct contact with specific foods (white fruits, tomato-based products)
• Coating: an organic coating must be applied to the inside surfaces of the tinplate container
• Function: preventing chemical reactions between product and container
• ECCS (Electrolytic Chromium/Chrome oxide coated Steel):
• Structure: electrolytically coating blackplate with a thin layer of chrome/chrome oxide
• Coating with an organic material to provide a complete corrosion-resistant surface
• Advantages: excellent key for adhesion of laminated materials added to the surface, less expensive than tinplate
• Disadvantages: matt surface, no reflective surface like tinplate
• Aluminum:
• Characteristics: used in a relatively pure form with Mn and Mg added to improve strength properties
• Not suitable for three-piece type containers, only used for seamless (two-piece type) containers
• Internal surfaces of aluminum containers are always coated with an organic lacquer
• Applications: carbonated beverages, collapsible tubes for food products (ketchup, cheese spread, chocolate)

Can Types

• Three-piece cans:
• Structure: consist of a cylindrical body rolled from a piece of flat metal with a longitudinal seam, together with two can ends which are seamed onto each end of the body
• Flexibility: possibility to produce any practical combination of height and diameter, suitable for making cans of different dimensions
• Container size flexibility facilitates the use of pack promotions, offering free extra product
• Two-piece cans:
• Structure: made from a disc of metal that is reformed into a cylinder with an integral end to become a seamless container
• Flexibility: possibility to produce any practical combination of height and diameter, suitable for making cans of different dimensions
• DRD cans: drawing, re-drawing, and ironing operations

Can Making

• 3-Piece Welded:
• Raw material: steel only, as aluminum is not suitable for welding
• Procedure: cutting coils of steel into sheets, coating and printing to protect and decorate the surfaces, slitting the sheets into small individual blanks, rolling the blank into a cylinder with two longitudinal edges overlapping, welding the edges, flanging the top and bottom of the can body, fitting the ends
• 2-Piece Drawn/Multiple (Re-Drawn) Cans:
• Raw material characteristics: sheets or coils of tinplate or aluminum, pre-coated, laminated, printed
• Body forming: I, II, III (multiple drawing and ironing operations)