PACKAGING OF DAIRY PRODUCTS

Module 5. Packaging of milk and milk products

Lesson 17
PASTEURIZED MILK

17.1 Introduction

The appropriate packaging of milk is of utmost importance not only to preserve its nutritive value and saving of wastage, but also to improve the marketability to achieve better returns. The challenge to the packaging industry is to deliver the nutritious milk to the consumer in most economical, hygienic, safe and environmentally friendly package.

There are two main types of packaging systems for fluid milk one is traditional bottling system in which container is to be returned and other is one way delivery in which container is disposable and does not travel back to the dairy. In the non-returnable distribution system there are several alternative systems where different packaging materials, shapes, sizes, forms and machines are employed for packs.

For selection of a suitable package material, the knowledge of important characteristics of milk/ milk products is essential.

17.2 Characteristics of Pasteurized Milk

1. Milk has a tendency to absorb the flavours from its environment.

2. Risk of Contamination is more in liquid milk.

3. Adulteration can be done easily when not packed properly.

4. It is difficult to handle milk in bulk quantities.

5. Milk is prone for oxidation when exposed to sun light

17.3 Criteria for Selection of Milk Packaging Material for Pasteurized Milk

Milk, an extremely perishable and sensitive product, need exact packaging material in order to preserve its initial quality for some span of time. The necessary characteristics of packages for pasteurized milk are:

1. It should be free from off-flavours.

2. It should not impart any taste or flavour to the product.

3. It should act as barrier to bacterial contamination,

4. It should be resistant to UV light ( max transmission: 8% at 500 nm & 2% at 400nm).

5. It should have no physiological effects on the products .

6. It should possess good mechanical properties (sealing, tensile, structural strength etc).

7. It should be tamper proof.

8. It should possess good oxygen barrier properties.

9. It should be economical.

10. It should fit in to processing- in-Line.

17.4 Materials Used

1. Glass

2. Plastics: (1) LDPE is widely used (2) LLDPE: 25% thinner film used and LDPE and LLDPE in 5:1 to 4:1 ratio.

3. Others: Coated paper board, wax coated paper board ESL ( Extended Shelf life Pouch )

17.5 Classification of Milk Packaging Systems

Classification of milk packaging materials can be done broadly in two categories which can be seen from the below flow diagram.

Milk is packed in various packaging materials according to the market requirement and table below describes the packaging material that is commonly in use.

Table 17.1 Types of packaging materials used for milk packaging

Of the total milk packed, flexible pouches dominate followed by aseptic packaging whose usage level is increasing day by day. Flexible pouches have proved to be a safe, quick and cost effective packaging method and with a wide distribution network, providing ease of packaging and handling. A good consumer response to milk pouches paved the way for the technological changes. In the form-fill-seal (FFS) system, the plastic film is formed into a tube, sealed along its length, sealed at the bottom to form a pouch, filled with milk and then sealed at the top. Butane LLDPE or C-4 and Octane LLDPE or C-8 is widely used because of their excellent cold storage properties.

17.5.1 Glass bottles

Packaging of milk in glass bottles is the oldest system. Clear glass bottles of 500ml capacity conforming to IS: 1392 – 1967 are used. The glass bottles offer certain advantages like transparency, rigidity, hygienic and non-toxic nature and compatibility. This system involves collection and transportation of empty bottles to processing plant, washing and sterilization of dairy bottles. This packaging system requires large storage space requirement for both empty as well as filled bottles. These factors increase the fixed and the variable costs. Heavy weight, fragility and return ability of bottles has inconvenience both to the distributor as to the well as consumer which made this packaging system undesirable and is not in use at present.

17.5.2 Returnable plastic bottles

Plastic bottles reduce the weight and the chances of breakage are rare but most other characteristics of packaging milk in glass bottles remain same.

17.5.3 Non-returnable plastic bottles

This system reduces transport charges through light weight and one way of delivery of bottles in a convenient way in comparison to any other system.
Ex: HDPE with PP lid, car buoy.

17.5.3.1 Plastic films

Plastic pouches are generally made of low-density polyethylene (LDPE) film. Co-extruded LDPE-LLDPE film is also used because of its advantage of eliminating pin-hole problems. The films are of 45-75µ thick. The pouches are formed and filled on form-fill-seal (FFS) machines in capacities of 200, 500ml and 1000 ml. The film should confirm to IS: 11805 – 1999. The plastic pouches are clean, hygienic and safe for this application and since these are not reused, the cleaning operation is eliminated and energy loss is avoided. Moreover, these pouches are easily recyclable for other purpose.

17.5.3.1.1 Developments in milk packaging in plastic pouches

The milk pouch concept actually originated in Europe with late fifties and had received growing popularity among consumers because of its convenience and reduced costs. Polyethylene, particularly LDPE has been used for packing milk. In Czechoslovakia milk was packed in 0.09 mm think white pigmented film. In Denmark and Finland, milk has been packaged mostly in co- extruded PE laminate consisting of a black inner layer and white outer layer. Similar packaging was also used in India by certain Dairies. In North America clear plastic material is used. The thickness of LDPE film got gradually reduced to 55μ- 65 μ. Now a days, in India milk pouches are formed from LLDPE film of 50-55 μ thickness.

17.5.3.2 Aseptic packaging of milk

Aseptic or long-life milk was originally introduced in Sweden in the early 1960’s originally called the “Tetra-pack” system. It utilizes a laminate pre sterilizer and a filling environment heater. Aluminium foil is an integral part of the flexible laminate in order to provide a barrier against light and gas. In UHT processing, Milk is preheated to 73– 850C then rapidly raised to 135°C for fraction of second and then suddenly cooled by flashing into a vacuum chamber. It must be packed under completely sterile conditions. No refrigeration is necessary for at least 3-6 months. If kept under refrigeration a self life of up to 1 year is possible.

In the distribution system, the pouches are placed in reusable multi-trip plastic crates. The crates are made of HDPE or PP and packs are nestable and stackable. The plastic crates shall confirm to specifications laid down in IS: 11584 – 1986.