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PET packaging for milk - The evolution and revolution
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Sunday, 01 June, 2014, 08 : 00 AM [IST]
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Shailesh Jadhav
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fiogf49gjkf0d Milk is one of the most nourishing drinks on the planet. It is consumed by more than 6 billion people worldwide, majority of these people live in developing countries. Since the early 1960s, per capita milk consumption in developing countries has increased almost twofold.
Per capita milk consumption
High (> 150 kg/capita/year) in Argentina, Armenia, Australia, Costa Rica, Europe, Israel, Kyrgyzstan, North America and Pakistan;
Medium (30 to 150 kg/capita/year) in India, Islamic Republic of Iran, Japan, Kenya, Mexico, Mongolia, New Zealand, North and Southern Africa, most of the Near East and most of Latin America and the Caribbean
Low (< 30 kg/capita/year) in China, Ethiopia, most of Central Africa and most of East and Southeast Asia. In South Asia, the consumption of milk and milk products is expected to increase by 125 per cent by 2030.
Reference: http://www.fao.org/agriculture/dairy-gateway/milk-and-milk-products/en/#.U4LiooGSxmw
One of the largest in the world
With large population size, India is one of the world’s largest producers and consumers of milk. Total annual production of milk in India is estimated to be 110 million tonne. Over the last five years, India's milk production has increased by about 25 million tonne compared to an increase of about 6.6 million tonne in the United States, 5.4 million tonne in China, 2.7 million tonne in New Zealand and 1.6 million tonne in the European Union.
Milk is liquid and requires containers at every stage of movement: production, storage, transport, distribution and marketing. The design of packaging for milk is determined by the demand for the product, the environmental awareness, consumer market and the new technology development. The selection of best material to satisfy the design criteria is to prevent the interaction of the food products with external environment from the time it is packaged till the product is consumed, and at the same time reduces the energy use and the environmental impact during the life of this product as that is very important during the design process.
Glass bottles to plastic pouches
Earlier packaging material used for milk was traditionally in refillable glass bottles. But today it is available in plastic pouches, Tetra Paks and plastic containers of various composition and constructions. The packaging material used in milk packaging should also serve the purpose of protecting of the flavour and nutritional qualities of milk. That is why one of the very important concern for packaging with respect to milk is need to store away from light, if it is packed in transparent containers. Milk gets easily deteriorated by the amount of light passing through the container wall depending on the material, from which the container is made, and also because of any pigment either incorporated into the material or used in printing it. The nature of the pigment also determines the wavelength of the light reaching the milk.
Innovative packaging technologies for milk are very important in the distribution process, development of extended life of the product, storage and the value added to the food and food products. Among all the plastic materials that are used in packaging of milk, PET (Polyethylene terephthalate) is gaining popularity and is being looked at as an alternative material for packaging of milk. The major advantage of PET is that it does not contaminate the content.
Further, it is lightweight and has strength. The material is resistant to breakage unlike glass. But it has a disadvantage - light transparency. However, this can be overcome with different treatment layer applied over the surface or by use of an intermediate layer during multilayer structure.
Light transmission
Studies have shown that unpigmented HDPE (High-density polyethylene) milk bottle in the 350-800 nm spectral region have been found to transmit 58%-79% of the incident light. Light transmission was reduced by pigmenting with TiO2 (1.6%) with the bottle being opaque below 390 nm. The use of colorant with the TiO2 pigment further reduced transmission of light with wavelengths less than 600 nm. The unprinted area of a paper board carton had less than 15% transmission below 550 nm and was opaque to wavelength below 430 nm. The effect of prolonged light exposure on the chemical changes in whole and 2% fat pasteurised milk stored at 4oC in clear PET bottle was compared with milk store in green PET bottle, PET bottle incorporating a UV blocker, PET bottle with exterior labels, HDPE jugs and LDPE (Low-density polyethylene) pouches. The milk stored in the green pet bottle experienced less lipid oxidation and Vitamin A loss than milk stored in clear PET bottles, HDPE jugs or LDPE pouches. The PET bottle with UV blockers slowed Vitamin A degradation but had little effect on the lipid oxidation, blocking visible light with translucent labels helped to inhibit lipid oxidation and Vitamin A degradation.
Single-use to multi-use
PET bottles are stretched blow mould from PET preforms in sizes ranging from 250 ml to 2 L. They are superior to HDPE bottle in terms of their mechanical and optical properties, their lower flavour scalping potential and substantially lower gas permeability values. For example, the oxygen transmission rate (OTR) at 4oC / 50% relative humidity (RH) of the commercial 600 ml PET bottle in 19µLday-1 compared to 390-460µl-1 day for commercial 600 ml HDPE bottle. Due to almost complete transparency of PET to light, milk bottles are either labelled or even better sleeved using heat shrinkable film polypropylene labels. Today most PET is wide necked 35-40 mm diameter and sealed with rigid PP screw caps. Beside full fat, semi-skimmed and skimmed milk, PET bottles are also used to package flavoured milk such as vanilla, elaichi, chocolate and strawberry, cultured milk and micro filtered milk. Even though PET bottles used by the dairy industry are single use, other industries such as carbonated soft drink are considering multi-use PET bottles.
Another area where there is significant development is done in PET bottle, is the technology developed by joint cooperation between Kortec and Sidel in developing PET bottle with 100% Light-Blocking Capability for Protection of Milk and Other Light-Sensitive Products. The preforms, developed by Kortec in cooperation with Sidel, consist of three layers of PET: white on the outside, black in the middle, and white on the inside. This approach ensures that the light-blocking black PET layer covers the whole of the bottle, including the base, thereby providing no access for light. The finished bottles, which were developed by Sidel, provide a great package for delivering light-sensitive beverages safely and attractively to customers.
Aseptic filling
Another area in milk packaging is use of aseptic filling for milk. Ultra-high temperature (UHT) treatment associated with aseptic bottle filling technology is an important strategic choice for dairy and beverages industries. From a marketing perspective, aseptic filling (such as hot filling and retort technology) offers many benefits to the consumer, and in comparison with chilled products, the shelf life is extended, hygiene and food safety are enhanced, making storage convenient and outside the cold chain. Aseptically filled bottles are easy to handle, resealable and shock-resistant. The bottle is also a good way of standing out from competition on-shelf and is a new way of expanding the refrigerated milk and milk beverages market.
Concerning aseptic filling of low acid products such as UHT milks and dairy beverages, it has substantial quality advantages versus retort technology. Long-life, shelf-stable milk used to be packed in bottles using autoclaving technology – milk being firstly UHT, processed then filled and sealed on a conventional machine before in-bottle sterilisation with temperatures ranging between 110°C and 120°C over 10-15 seconds (depending on the technology). Aseptic filling in bottles involves UHT treatment, the product being then cooled down to 20°C before aseptic filling with no further heat-treatment. The organoleptic quality of aseptically processed UHT milk shows significant benefits in terms of lactulose, lactoserum proteins and vitamin content. Aseptic packaging also avoids a cooked taste due to Maillard reaction or caramelisation.
Aseptic packaging in bottles is well suited to dairy beverages with high added value and a delicate formulation. For instance, where the added vitamins would not bear further heat treatment. This includes flavoured milk and all low-acid drinks such as ready-to-drink (RTD) coffee, baby milk and nutritional milks, and where an overcooked taste is a major drawback (as in white milk). Finally, aseptic filling in bottles achieves a consistently high grade of food safety.
Long-term impact
Currently in Indian market we find Amul has already launched its brand Amul Kool lassi and flavoured milk in PET bottle, which will definitely be competing with beverages that are available from Indian companies as well as MNCs and will create a new foray for itself to stand in this highly competitive beverages market. But in long-term, we also need to see how this creates an impact on the customers and increase its saleability. But recently a life cycle assessment conducted by the Institute for Energy and Environmental Research (IFEU) has confirmed that compared to disposable HDPE and PET bottles, carton packs for UHT milk have a significantly better environmental profile - particularly with respect to CO2 emission, use of fossil resources and consumption of primary energy. So we need to look further to this area too which will definitely impact us in long term.
Reference:
Food packaging and shelf life a packaging guide-Gordon L. Robertson
Food Packaging Principles and Practice-Gordon L. Robertson
(The author is freelance business consultant-packaging & printing. He can be contacted at shailesh_02@yahoo.co.in)
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