Packaging materials

All the packaging material used for dairy products can be classified into 3 categories i.e. Flexible, rigid and semi rigid. Different materials under these 3 categories are discussed below:

Flexible Packaging Materials

It has been estimated that there would be average growth of 20-25% of consumption of flexible packaging materials by the end of 2010 A.D. Different types of Flexible material used for packaging milk and milk products is discussed below.

i) Paper and Paper Board

Paper could be simply explained as a combination of fibres, joined together by means of binding agent. However, a number of chemicals are also used to improve different properties of paper like brightness, opacity, strength properties etc. Paper and paper boards can be clearly differentiated by considering the grammage (gms/sq.metre). More than 180 grammage papers are called as paper board. Paper boards are having certain improved properties like high stiffness, high bending resistance and less water absorption etc.

Types of Paper and Paper Boards

Depending upon the properties, there are different types of paper and paper boards which have got wide application in packaging of dairy products. The details are as follows:

Paper

Tissue paper, Coated paper (Varnish coated, wax coated, plastic coated),Glassine paper, Art Paper, Kraft Paper , VPI paper, High Gloss Paper,Vegetable parchment paper and Grease proof paper (G.P.P)

Paper Boards

Duplex Board, Clay coated board, Triplex Board, Kraft Board, Coated board, Chip Board, Asphalted board, Straw board, Grey Board and Mill board

Properties of Paper Paper is used for the packaging due to the following advantages.

(1) Flexible in nature, (2) Easy amenable to printing, (3) Easy amenable to any kind of coating, (4) Good temperature resistance either high or low, (5)Excellent properties towards recycling, (6) High strength properties (7) Good insulation properties, (8) High gloss properties on smooth side (i.e. felt side), (9) Could be manufactured with high brightness properties, (10) Excellent folding endurance properties, (11) Good tear resistance Properties and (12) Compatibility with other packaging materials for lamination.

Properties for Paper Board

(1) Paper boards are having all the properties of paper, (2) In addition, these materials are having good dead fold characteristics, (3) High stiffness Properties,(4) Amenability to fabricate folding cartons, display carton etc. and (5) Less cobb value as compared to paper.

Application for Dairy Products

(1) Grease proof or butter paper is used for packaging of butter

(2) Lined cartons are used for packaging of ghee

(3) Folding cartons are used as intermediate packages for butter, milk based confectioneries etc.

(4) Paper board is used as an important substrate for aseptic carton

(5) Chip board is also used for the packaging of milk based Indian sweets like rasogulla, gulab jamun, sandesh, burfi etc.

ii) Aluminium Foils

What is Aluminium Foil

Aluminium foil is a continuous web/sheet of aluminium metal rolled to thickness/ gauges ranging from 0.005mm to 0.2mm. It is produced from commercial puriety aluminium with aluminium content of not less than 98% purer metal with 99.8% content is of more interest to the electrical industry. It is available as free unsupported or unlaminated or laminated to paper or film. It is available in plain, coloured, coated, lubricated and embossed forms.

Properties of Aluminium Foils

The important properties are as follows :

(i) Impermeable, (ii) Non Toxic, (iii) Stable, (iv) Light, and heat barriers,(v) Tasteless and Odourless, (vi) Tagger, (vii) Tea chest lining, (viii) Stand up pouches, (ix) Retort pouch and (x) Multilayer laminates:

 Advantages of Foil

i. Tearing properties facilitates to use as sealing surface in the blister pack.

ii. Extensively used for lamination due to impermeable properties.

iii) Plastic Materials

“A plastic material is solid at ordinary temperatures and allows appreciable and permanent change of form without losing its coherence on the application of pressure and heat.” Plastic materials are perhaps the most versatile group of materials used in packaging. The plastic resins are generally categorised in two ways i.e. thermoset and thermoplastic resin.

Some of the important thermoplastic materials which have got extensive application in packaging like polyethylene, polypropylene, polyvinyl chloride, polyester, nylon or polyamide, polystyrene etc. These polymeric materials are normally classified into different group based on the polymerisation process and molecular structure like

(a) Polyolefins - Polyethylene and Polypropylene (PP)

(b) Polyvinyl group - Polyvinyl Chloride (PVC)

(c) Condensation - Polyester(PET), Nylon-6 or Polyamide (PA)

(d) Styrene Polymers - Polystyrene (PS) and Expanded polystyrene (EPS)

(e) Carbonate group - Polycarbonate (PC)

(a) Polyolefins Groups

The properties of different polymeric films are as follows :

Low density Polyethylene (LDPE) film

Density ranges from 0.910 – 0.925 gms/cc, Average molecular weight is 3 x 105, Resistance to heat is about 180 – 2120F, Translucent type of clarity, Water absorption is 0.015%, Permeability to gas is 1.0 cc/m2/ 24hrs at 270C & 1 atmospheric pr., Good tensile strength properties & high percentage of elongation,Good dart impact resistance, Resistance to the effect of weak acids and alkalies and Good barrier to moisture vapour.

Linear Low Density Polyethylene (LLDPE)

High film tensile strength properties as compared to LDPE, High percentage of elongation as compared to LDPE, High tear strength properties, Better stress crack resistance and low temperature brittleness, Improved stiffness properties,Excellent Puncture resistance and Excellent heat seal properties.

Medium Density Polyetheylene (MDPE) film

Density varies from 0.926 – 0.940 gm/cc, Average molecular weight is 2 x 105,Resistance to heat is 220 – 2500F, Translucent type of clarity, Percentage of water absorption is 0.01, Permeability to gas is 1.33 cc/m2/24 hrs at 270 & 1 atms. Pressure, Very resistance to the effect of weak acids, alkalies etc. Exposure to sunlight turn its colour to yellowish.

High Density Polyethylene (HDPE) film

Density varies from 0.941 – 0.965 gm/cc, Average molecular weight is 1.25 x 105, Resistance to heat is 2500F, Opaque in nature, High barrier to moisture vapour, Permeability to gas is less as compared to other polyethylene film and exposure to sunlight turn it yellowish.

High molecular high density polyethylene film (HMHDPE)

High mechanical strength in both directions, Has got pleasant translucence in clarity, High tear resistance properties, Does not impart any taste or odour,Suitable for food contact application, Less elongation as compared to other polyethylene film and Excellent moisture barrier properties.

(vi) Polypropylene (PP) film

High tensile strength, High chemical resistance and high temperature performance than HDPE.Very low permeability to moisture vapour and gas compared to polyethylene,High transparency, Chemical inertness and High softing point.

(b) Polyvinyl Chloride (PVC)

It is hard, brittle and transparent materials, Low GTR, Moderate WVTR and good resistance to fat and oil, Glass like clarity, Good mechanical strength, Retention of flavour, Excellent printability, Lower weight/ volume ratio and Resistance to chemicals.

(c) Condensation Polymer

Polyester film (PEF) film

It has got excellent gloss & thus enhance sales appeal.

Very Low moisture and gas permeability.

High mechanical strength.

Resistance to tear, puncture, burst and flex crack.

Dimensionally stable over a wide range of temp. from 70C0 to + 1300C

Excellent machinability.

Excellent printability

Light in weight & thus economise the transport expenditure.

Free from all kinds of additives and thus does not contribute off flavours

Good surface properties for metallization.

Polyamide or Nylon-6 film

High mechanical strength, High elongation capability, Excellent resistance to cutting, perforation, abrasion and bursting, High chemical resistance to oils and fats,Outstanding impermeability to gases and vapours, Easy printability, Easy metallising, Economical (considering best yield/kg) and Could be biaxially oriented.

(d) Styrene Polymers Polystyrene (PS)

Polystyrene is not flexible in nature unlike LDPE and PP and is mostly used as rigid containers in the field of packaging. The important features or properties of this polymer are as follows :

Crystal clarity of containers, Availability in attractive light or dark colours,Lustrous finish, Rigidity and dimensional stability, Resistance to chemicals,Easy processing, Good barrier to moisture and ability to take post moulding decorations like hot stamp foiling, screen printing, inlay foil moulding etc.

Expanded Polystyrene (EPS)

Expanded polystyrene (EPS) is neither flexible nor rigid in nature rather the materials are cushioning in nature. Normally, these materials are called as ‘thermocole’.

The important properties of this material are as follows :

Fully resistant to dilute acid, alkalis, alcohols, sea water but reacts with aliphatic hydro carbons, ketones etc., The density (kg/m3) varies from 20-30, Stress at 10% compression (kg/cm2) is 1 to 1.4, Shear strength (kg/cm2) from 6 to 8,Flexural Strength (kg/cm2) ranges from 2.5 to 3, Tensile strength (kg/cm2) is from 2.5 to 3.2, Thermal conductivity at 100C (k. cal. m/hr. m2 0C) is 0.028, Water vapour transmission rate is ranging from 0.6 to 1 gms/m2/14hrs at 380C & 90% RH, Water absorption % volume after 7 days immersion is 0.6, Has no nutritive value for any known organism and does not provide a breeding ground for fungi, bacteria or insects and its contact with food stuff is perfectly safe.

Multilayer Plastic Film

In order to have all the properties in a single form of polymeric materials so as to meet the requirement of processed food products especially for dairy products with desired shelf-life, a remarkable development has taken place to produce multiplayer plastic film either as laminate form or Co-extruded form.

Properties of multi layer Co-extruded Plastic films

High barrier properties to moisture and oxygen gas, improved in flexural endurance properties, dart impact strength properties is increased, no possibility of delamination of individual layer unlike laminates, Cheaper as compared to laminates and amenable to easy printing on surface.