Foodstuffs such as milk, for example, are very sensitive as regards their shelf life. Hereby the right packaging plays a decisive role. Multilayer packaging products based on the co-injection technology are clearly at an advantage. They are not only flexible, safe and economically efficient, but also unobjectionable from the point of view of the law on foodstuffs.

It’s the season of the alpine pastures in Jenaz (Grisons/Switzerland). Each year after the last snow has melted away and the young grass gives the slopes a first pale green, a herd of about 90 cows leaves the village of Jenaz and starts the steep ascent to the Larein Alp. The site extends over an area of 175 hectares of pastureland and approx. 50 hectares of forest meadows. The cattle alp starts at 1550 metres above sea level and reaches up to the ridge of the Glattwang mountain at 2376 metres.

Old Swiss tradition.
Alpine farming has a long tradition in the alpine regions. There is evidence of alpine pastures having been set up since five thousand years BC. From the 11th to the 12th century the mountain grassland used to belong mostly to nobility or monasteries and was let to individual farmers or farming cooperatives. In the course of time the tenants were able to buy parts and later on entire alpine operations from the ecclesiastical and grand owners. Today the roughly 7300 summer alpine operations of Switzerland are to 50 per cent each in the hands of private persons or corporations.

Off to the heights.
The first leg covered by the cows of Jenaz ends at the lower-level barns. Larein has alpine barns and facilities at two levels, like most Swiss alpine pasturelands. As the grass ripens for grazing at different times during the season depending on the altitude, the pastures are used from the bottom upwards in the early summer and downwards towards autumn.

Mountains of hard work.
The summer season during which the cows are on the alpine pastures lasts about 100 days. One alpine dairyman and two aids live and work on the Larein Alp during this period. The days are hard and long. Heavy physical work and arduous long walks characterize everyday life in the mountains. The weather is far from always fine and can confront the workers with strong winds, heavy rain and severe cold even in midsummer.

Quality at the highest level.
The mixture of barrenness, variety and naturalness, however, has its distinct advantages. Nature in the mountains is generous and provides the cows with the very best grasses and herbs. The Larein Alp and the slightly higher located Nova Alp yield a total of 140,000 kilos of the finest alpine milk in one season. A part of this milk is processed to different dairy products directly on site. Larein produces 6500 kilos of alpine cheese, 650 kilos of alpine butter and 200 kilos of green cheese. The products are extremely popular down in the valley and in the cities. At the end of the season, the time of descent from the alp, they are transported down and sold.

Considering the environment, it isn’t surprising that the alpine milk is superior to milk from the valley. Anyone uncertain of his/her sense of taste can look it up in studies. Research has confirmed that milk from the alps contains more substances conducive to the human health than the ordinary type.

Maintaining goodness isn’t easy.
The task is to bring this extra value in the milk without impairment to the consumer. Gentle processing is one aspect. Antiseptic conditions, perfectly cleaned and sterilized processing equipment, low-germ ambient air and the least possible interference during the filling process are the basis of a correct treatment. Any deficiencies in the process cause the milk to lose its vitamin content, assume an unwanted flavour or get contaminated by a foreign substance.

Suitable packaging.
Special receptacles are needed to ensure that the milk from the Larein Alp doesn’t lose any of its healthy effects until it reaches the consumer. The product’s shelf life depends decisively on the properties of the container’s outer wall. Light transmissiveness, aroma protection as well as oxygen barriers are the biggest influencing factors. If the container offers sufficient protection, the milk lasts longer, the oxidation of the lacto fats and changes in taste are delayed.

The right technology.
Three technologies are currently available to improve the shelf life. A first variant are material mixtures which provide barrier functions. The second possibility is to work with inner or outer liners of the finished container. The third technology is the co-injection process which is gaining ever greater significance in the foodstuffs industry. Here the barrier material is injected as an individual layer into the preform wall so that later on, when the preform has become a bottle, neither the liquid inside nor outside influences come into contact with the actual barrier.

Pluses of co-injection.
On closer examination it is evident that the co-injection technology brings the best results. With material mixtures the preform price can be up to 85 per cent higher and recycling is impossible. Inner and outer liners can get damaged or contaminate the filled medium. Seeing that the coating is applied to the finished container, the logistics mustn’t be underestimated, either. Recycling of the coated containers requires a higher effort additionally.

Barrier injection moulding is currently the most flexible, safest and most economical technology and is likely to remain so in the near future. Flexible, because preforms with a barrier layer need only smallest adaptations to a preform mould and further processing can take place on any standard machine. Safety is guaranteed by co-injection in that the barrier is protected inside the bottle’s inner and outer wall without coming into contact with the content. The economic benefits are clearly the flexibility and the relatively low extra costs.

Barrier which works.
Co-injection allows in principle the use of all presently known and future barrier materials. This permits to take over all innovations on the market without further effort.

Protected advantages.
Let’s get more concrete. The multi-layer bottle for the delicious alpine milk is made from a preform which features a black barrier layer in its core. This makes the bottle virtually light-impermeable (≤ = 0.05%), a fact which is absolutely decisive for the nutritional value and the taste of the milk. In spite of the ideal barrier there are no restrictions as regards the design of the bottle. On top of all this the multi-layer milk bottles are fully recyclable and meet the applicable regulations on foodstuffs.

Co-injection convinces.
Compared with mixed materials and coatings, the co-injection technology has the advantages clearly on its side. Looked at technically, two injection units are required on the moulding machine, but only one hotrunner in the mould through which the two components are injected. This means that new barrier materials can normally be processed in the existing mould system with only a minor extra financial effort. The co-injection technology will remain highly attractive for the production of multi-layer preforms and bottles also in future.

The advantages of the co-injection technology:

• Standard injection moulding machine featuring a second injection unit
• Known and well-proven mould engineering
• Only marginally increased preform wall section
• Unobjectionable from the point-of-view of the law on foodstuffs
• Excellent protection of the aroma
• Very good gas barrier
• Shelf life of the content is extended and guaranteed
• Lowest cost per bottle compared with other technologies

Write comment