Packaging of Milk and Milk Products

Packaging is the technique of using the most appropriate containers to protect, carry, identify, and market any product. It constitutes a vital link between the manufacturer and the eventual consumer for the safe delivery of the product through the various stages of manufacture, storage, transportation, distribution, and marketing.
As a result of socio-economic changes, packaging has become increasingly important in the scheme of distribution. The criteria by which a package is judged are usually the following:

It must protect and preserve the commodity from the time it is packed to the point of consumption.
It must be suitable for the chosen selling and distribution system.
It must be attractive to the consumer, easy to open, store and dispose of, and inexpensive in cost.

The package should be adequately large to hold the product. It should have proper constructional features to prevent spillage. It should have enough strength to withstand handling, transportation, and storage hazards. Finally, it should be as compatible as possible with the product.
It should also safeguard the product against contamination or loss and damage or degradation due to microbial action, exposure to heat, light, moisture, and oxygen, accidental spillage, evaporation, pilferage, etc. The shape of the package should be favourable to dispensation and reclosure and to its disposal or reuse.
A container of good quality should have the following characteristics:

It should be made of materials that do not have any tendency to transmit the slightest trace of their constituents to the product.
It should not be vulnerable to attack by either packaging materials or cleaning agents. This is essential for two reasons: attack of the internal walls of the container by such products may cause a change in the milk composition and may further cause pitting of the walls where bacterial colonies, difficult to eliminate, could proliferate.
It should be such as to avoid, as far as possible, all indirect or direct chemical change in the components of milk and, in particular, the oxidation of lipids.

Table of Contents

Adaptation to type of milk

Each type of milk requires a container adapted to it, which should accordingly be designed in relation to its function. A bottle of pasteurized milk does not have the same characteristics as a bottle of sterilized milk.

Packaging of pasteurized milk

The packages used for the distribution of pasteurized milk comprise cans, glass bottles, and single-service containers.

Milk cans

Cans of 20 or 40 liters capacity are usually used to supply milk in bulk.

Glass bottles

The bottle is gradually replacing the can for the distribution of processed milk. Despite its weight and problems arising from breakage, sterilization, and the return of empty bottles, the bottle is widely used as a milk container.

Glass bottle fillers

There are two types of automatic bottle fillers. The first is the gravity type filler in which the milk flows by gravity into the bottles as they are pressed against the valves. The second type is the vacuum filler in which the milk is ‘pulled’ into the bottle by vacuum exerted on the inside of the bottle.
One of the limitations of the gravity type filler is its comparatively slow filling speed. To fill a large number of bottles in a short time, numerous filler valves around the outer periphery of the bowl are necessary. The vacuum filler was designed to overcome this drawback.
Many modifications in vacuum-type fillers are possible by using different valves and varying degrees of vacuum. In a single-bowl vacuum filler, the bowl having open vent tubes and conventional gravity valves is closed with an airtight cover. A pipe supplies milk through a sealed closure at the center of the cover to a float valve in the bowl. Air above the milk level is drawn off through a vacuum line that is centered around the supply pipe. Thus, air is drawn from the bottle through the vent tube as soon as the bottle makes contact with the valves. Milk and foam in the vent tube are drawn into the tank as soon as the contact is broken.

Single-service container

Appreciable progress in the use of single-service containers for the packaging of pasteurized milk has been made in recent years. The advantages of single-service containers as compared to bottles may be briefly summarized as:

Resistance to tempering
Reduction in forms of volume and weight carried by distribution milk vans
No return of empty containers
Less labour requirement
No cleaning problems

Opacity protects milk against the action of light, which catalyzes the oxidation process that may alter the milk’s flavour. From the bacteriological point of view, there is not much difference between a well-washed bottle and a single-service container.
The hygienic value of these containers is determined by their leakproof and stable inner lining. The lining should not contain toxic products and should be proof against attack by milk constituents.
The development of the Swedish Tetra Pak recently has given new impetus to single-service packaging. The principle of this package is to form a tetrahedron from a single strip of paper. The strip is sealed along its parallel edges to form a tube, the base of which is cut and joined to form one edge of the tetrahedron. The required quantity of milk is introduced, and the other end of the tube is cut and sealed by a clamp to form an edge perpendicular to the preceding one.

Packaging of milk in low-density polyethylene bags (sachets)

This type of single-service container is being used to deliver milk to consumers in metropolitan cities of India. The required amount of milk, say 250 ml, 500 ml, and 1000 ml, can be filled by an automatic pre-pac machine.

Precautions:

Ensure proper power supply.
Ensure proper air pressure before operation of the machine.
Ensure proper water supply to heaters and milk supply to the overhead tank.
Adjust sealers at proper temperatures.
Do not touch any moving part of a machine that is in operation.
Ensure proper sealing.
Ensure that proper vacuum is maintained in a bottle filler.
Ensure that the compressed air supplied to the capping unit of a bottle filter is at adequate pressure.
Ensure that the aluminum foil used for capping of bottles conforms to prescribed specifications.
Ensure that warm bottles are not fed to the filter to avoid breakage during filling.

Procedure:

A. Pre-pac machine (Sachet filling machine):

Load the polyethylene roll.
Start water supply to the heaters of the pre-pac machine.
Switch on the main sub-electric panel for power supply.
Switch on the compressor for getting a supply of compressed air.
Switch on the motor of the pre-pac machine.
Switch on the vertical sealer.
Close the valve of the overhead balance tank.
Start the milk supply to the overhead balance tank.
Push the button for packing the required quantity of milk in sachets.
Push the button to inject milk into the cylindrical tube of polyethylene.
Adjust the temperature of the vertical and horizontal sealers.
Push the button for horizontal sealing.

The required quantity of milk will be delivered into the vertically sealed polyethylene tube, and it will be sealed horizontally and cut by a knife placed just below the horizontal sealer. The pre-pac machine will work automatically.

B. Gravo-type filler:

Start the vacuum outfit and maintain the desired vacuum in the filter.
Start the air compressor.
Supply milk to the filler from an overhead tank.
Fit the aluminum foil on the bottle capper.
Start the filler.
Bottles are fed to the filler directly from the bottle washer by conveyor.
See that the bottles are mechanically centered on the lifters located directly under the filling valves and revolving with them.
See that when the bottle comes in contact with the valve rubber, the valve lifts and that the bottle is evacuated up through the tube.
See that the valve is opened and the pressure inside the bottle is reduced so that milk can flow into the bottle.
See that when the bottle is full, the milk rises in the vent tube up to the level of the milk in the filler bowl.
See that the filled bottle is then transferred to a capper where it is automatically sealed, and the lifter, now in the lowered position, is ready to receive another empty bottle for filling.
Collect the bottles in crates on the accumulator table and transfer to the crate conveyor.
The timing of a bottle filler and capper is of utmost importance; however, see that the filler valves, the bottle feed, loading and unloading wheels, the bottle lifter, and the capping mechanism are synchronized.
Keep the bottles in the cold store at 5-10°C until distribution and sale.