Packaging of Dairy Products

Module 3. Package forms

Lesson 15 A
FORMS OF PACKAGES USED FOR PACKAGING OF FOOD AND DAIRY PRODUCTS

15.1 Introduction

In this lesson the topics related to different forms of package like foils, containers, jars, blister packs, pouches etc are discussed in detail.

15.2 Developments in Package Forms

• In Paleolithic times, food was consumed where found and when needed, man used natural containers such as hollow tree trunks, gourds, hollow rocks, shells, leaves and pieces of bark.

• In later times man learned to fashion containers from natural materials. He deliberately hollowed out logs of stones, and animal parts used such as bladders, skins, horns, bones, sinews and hair.

• Mesolithic man stored food surpluses in baskets made of rushes and grasses.

• Neolithic man fashioned metal containers and discovered pottery.

• From prehistoric times until about 1200 AD the status of packaging could be summed up as follows:

• 6. The barrel, wooden box, ceramic jar or pot, leather bag and cloth sack are as old as civilization.

15.2.1 Common package forms

• Rigid Packages: They are formed in to a definite shape from a sufficiently strong materials, so that they retain their shape when filled with product and are not deformed unless subjected to sufficient force to destroy or severely damage the total structure. Eg. Metal, glass bottles, plastic cans etc.

• Semi-rigid Packages: They are formed in to a definite shape from less massive or weaker materials, so that although they are not intended to be distorted substantially when filled with product, but they can be distorted without severely damaging the total structure by the application of a moderate force. Eg. Collapsible tubes, Bag-in-box system.

• Flexible Packages: They are formed to a definite shape when empty but are made from sufficiently flexible materials that they generally confirm their shape to the product they contain and may be distorted or crushed with ease unless supported by the rigidity of the product. Eg. Flexible pouches & bags.

Some of the important package forms are discussed here.

15.3 Metal Boxes/Cans/Tins

With the invention of tinplate, the fabrication of soldered metal boxes was made possible. Boxes can be designed with embossed lettering or patterns, or printed paper labels can be applied. Also metal itself can be printed.

15.3.1 Metal cans

• Traditionally, cans have been made from soldered triplet steel. More recently aluminum can has been introduced. Today there are several more choices available: standard tinplate, light weight double reduced tinplate, tin free steel (coated), vacuum - deposited aluminum on steel and aluminum.

• Can bodies can be soldered, welded or cemented. Steel bodies can be combined with aluminum ends. Many new easy open devices are available for cans ranging from pop-tabs for beverages to complete removal of lids or panels for frozen or meat products.

• Can coatings are now regarded as vital components - especially for foods and beverages. Coatings must be non-toxic and free from odour or taste. They must not deteriorate or come loose from the can wall during food processing and storage. Interior coating are made from acrylics, alkyls, butadienes, epoxy amines, epoxy - esters, epoxy - phenolics, oleoresins, phenoics and vinyls depending upon the type of food and process. Outside coatings include acrylics, alkyds, oleoresins, phenolics and vinyls and are usually pigmented. They are less exposed to food contact but must survive processing and be receptive to further decorative coatings and inks.

• The tinplate is made of thin sheets (0.025mm thick) of mild steel coated on both sides with a layer of pure tin. The steel sheet is made by

• Hot Rolling - hot dipping in bath of molten tin.

• Cold Rolling or Electro tinning i.e. by electro decomposition from solution of tin salts - this process enables application of much smaller thickness of tin coatings.

• For packaging certain dairy products, it is desired to use an externally and internally lacquered can. Lacquer offers protection against corrosive attack by acids, discolouration etc. Protection offered by lacquer is not always complete, but pinhole leaks may give pitting corrosion. Production of hydrogen causes swelling of lacquer and ultimately perforation of the can. This increases the amount of lead and iron dissolved in canned foods. Lacquer reduces attack on tin and hence it will no longer act as sacrificial anode, hence amount of dissolved lead in food increases. In non - lacquered cans, iron is attacked only after extensive de-tinning. Once the can is opened, uptake of lead increases due to ingress of O2. It is more marked in case of unlacquered cans.

• The lacquered cans are made by passing the sheets of tinplate through rollers running in a bath of lacquer (a protective coating consisting of synthetic or natural resin and for cellulose acetate dissolved in a volatile solvent), which apply a thin coating to the sheet. The coated sheet is passed through a heated oven, which causes the lacquer to dry and harden. Such lacquered sheets can then be made into cans exactly as plain sheets.

Types of metal cans used for Dairy Products are:

15.3.2 Tin packaging

• It is one of the earliest food packages and tin can heralded the year-round supply of conveniently packaged food even before the science of food preservation was understood.

• As for the developments in the tin can, the stringent requirements of zero lead contamination of canned foods have led to complete replacement of soldered can by the welded one.

• Continuous efforts are on to improve and develop better can lacquers like polyester lacquer, and to reduce tin coating weights.

• Tin - free steel (TFS) can, an economic alternative to the open top sanitary (OTS) can is also being used extensively.

• With respect to developments in India, soldered can is being replaced gradually. A significant development is the partial replacement of imported tin plate with the indigenous one.

• For carbonated beverages, aluminum can have been dominating, because very thin walls can be used taking advantage of the internal pressure of the beverage to obtain structural rigidity and strength.

• With aluminum becoming costlier now, the recapture of a sizable market of the carbonated beverages by the 2 - piece steel can seems imminent. This is further strengthened by the newer research development which has made it possible to produce steel cans of extremely thin walls.

• Inspite of India being a major aluminum producer, the aluminum can has not yet come to be used widely, the reason being prohibitive cost. Hence it is used for special applications such as gift boxes and export purposes.

• Tinplate containers with ring open lids with or without re-closure facilities are used for larger quantities say 500 gm and more.

• Fancy containers having different shapes are used with friction lids and generally intended for after use applications. Alternatives to these types of traditional metal containers include composite cans, Tin Free Steel (TFS) cans and Plastic Containers.

15.3.3 Metal tubes

• Collapsible tubes were first made from soft metal for artist’s paints and replaced animal bladders

• They found early use in dispensing glues, medicinal salves and tooth pastes, but little use was made of them for food products until the past decade.

• Plastic collapsible tubes (MLCT) have come on the market containing sandwich pastes, cake icings, pudding toppings etc.

• The first closure of collapsible tubes was by a metal screw with double head.

• The moulded screw cap was a later innovation.