Part 3.1.2 - 1: Milk, cream, yoghurt and dairy desserts  Please click here to download the pdf. From its earliest use as a robust and non-corroding material for milk churns and the introduction of alufoil tops for glass milk bottles, aluminium has played a key role in the packaging of dairy products. Today, aluminium foil continues to answer the special needs of liquid dairy products and to facilitate the great changes in processing, packaging and distribution required to meet consumer demands. Important properties Barrier protection Foods containing oils or fats lose their nutritional value and flavour when exposed to light. The thinnest layer of alufoil in the packaging stops this process and acts as a complete barrier against loss of moisture and flavours as well as preventing contamination or unwanted external taints. Mechanical properties Light, yet strong, alufoil’s unique ‘deadfold’ characteristic makes it ideal for embossed surface designs, date coding etc. Readily laminated to other materials Alufoil can be easily laminated with other materials to provide additional properties, thus improving the performance of other flexible packaging substrates and making thinner laminates possible – so saving resources. Decorative potential Alufoil’s bright or matt metallic finish plus compatibility with all printing technologies provides designers with enormous scope to create packs with stunning graphic design and shelf presence. Hygiene, safety and product security At the end of its production process, alufoil is sterile thanks to high temperature annealing. This forms the basis of a very hygienic packaging material which can be delivered to a high level of sterility depending on the subsequent converting, printing, packaging and delivery conditions. Alufoil is safe for use in contact with foodstuffs, does not harbour or promote the growth of bacteria and is an ideal protection against product tampering. Sustainability Alufoil is weight-saving, effective and minimises the amount of packaging material needed. Added to this reduction at source, it also helps to preserve valuable dairy products, so cutting waste of food, materials and energy. Aluminium can be repeatedly recycled at a fraction of its original energy cost. Modern separation techniques allow aluminium foil in household waste to be extracted and recycled. Even in cases where the metal is uneconomic to recover directly, its high energy content can be efficiently recovered in the form of heat. Heat resistance and conductivity Alufoil can be heated to high temperatures without distorting or melting – ideal for autoclaving and heat-sealing processes.
Applications
Milk capping The well-proven method of bottle capping using aluminium foil introduced hygiene and high speed mechanisation to milk packaging and contributed to one of the most efficient forms of re-used pack. The used glass bottles are collected and re-filled again and again – so saving valuable material resources. The aluminium used for the cap can be recovered economically by recycling. This apparently ‘simple’ alufoil cap does several jobs. It can be printed or lacquered to identify the milk. Embossing by the bottling machine allows date-coding and identification. The inside surface of the foil may also be printed for special sales promotions.
Crimping the capping foil onto the rim of the bottle provides a secure closure. Also, aluminium’s intrinsic ‘deformation-hardening’ adds a high degree of grip where the maximum deformation occurs. Once opened, the foil cap provides a temporary reclosure. Heat-sealed caps and diaphragms for liquid milk The compatibility of aluminium foil with heat-seal lacquers coupled with the metal’s excellent heat conductivity and stability makes it the ideal material for capping and heat-sealing of all types of plastic milk containers. Whether the milk is fresh, aseptically filled or sterilised in the container, the foil/coating combination can be designed to meet the demands of processing and distribution. A foil diaphragm solves the problem of achieving a reliable screw-top closure for blow-moulded milk bottles. This is heat-sealed to the bottle opening using an induction heating technique. Only the metal foil becomes heated by a high frequency electro-magnetic field applied after filling and capping. Although reliably sealed, the foil can be peeled away cleanly thanks to coatings that combine seal strength with peelability. Lidding for cream, yoghurt and dairy desserts Much has been quietly evolving over recent years in the materials and techniques for dairy product lidding. Foil thicknesses have been steadily reduced thanks to greater sophistication in the selection of alloys and in their conditioning prior to printing, embossing and cutting. Traditionally embossed to ensure reliable handling on the lidding machinery, lids can now also be supplied without embossing. The separation characteristic is provided by a pattern of ‘dots’, messages or logo designs printed on the inner sealing side. Surface decoration has developed significantly over recent years to enable lid suppliers to combine comparatively low runs with very high grade multi-colour designs for competitive prices. This appeals to companies wishing to test market new products. Now even hotels and restaurants can have their own ‘brands’ of dairy products – breakfast yoghurt, cream portions, butter etc. without the cost barrier associated with lid printing. Advances in heat-sealing lacquers have also brought the consumer the convenience of peelability combined with the security of a reliable and temperature-controlled rim seal – which only a metal closure can offer. Scientific studies* have shown that opaque lids for dairy product containers can help to extend shelf life by protecting the sensitive contents from direct exposure to the strong fluorescent lighting in refrigerated supermarket display cabinets. Following a study into the comparative merits of lidding materials**, a major American producer of organic yoghurt products recently found that switching to alufoil from plastics reduces packaging waste at source by 270 tons. Lidding for milk and cream portion packs For the caterer, portion packs with a reliable seal coupled with a complete barrier to all contaminants and the facility for ease of opening, simplify the storage and serving of these sensitive foods. An alufoil closure completely eliminates spoilage due to exposure to the atmosphere, over-serving and deterioration during storage. Dairy desserts in alufoil containers The ideal package for heat-processed dessert products, the alufoil container has several advantages. The entire pack is opaque. No deterioration due to UV light is possible. The conductivity of the alufoil allows rapid heating, minimum processing time and rapid cooling. The decorative potential of the container can be seen from some of the examples on the market. In the case of the smoothwalled container format, pre-distorted printing allows for excellent graphics on the shaped dish. In a similar way to yoghurt or cream, lids can be decorated and either embossed with a pattern or entirely smooth. Milk and cream in cartons UHT sterilised milk packaged in alufoil lined flexible cartons is in very strong demand. In France, for example, the consumption per head of population is around 43 litres. An attitude study*** has shown that consumers see the carton as easy to store and keep in the refrigerator, good protection and environmentally friendly.
The preference of consumers for UHT cream in foil lined cartons was illustrated recently by figures showing that cartons dominate with over 85% of a market worth more than € 150 million in 2002. For the milk or cream packer, the one-way carton has several advantages: minimum handling and storage of packaging materials, no cost of glass bottle processing, minimum weight, space and transport needs for the packed product and excellent graphics and display characteristics. *A review entitled The Effects of Light on Food by Miray Bekbolet of the Tubitak-Marmara Research Centre, Department of Nutrition and Food Technology, Gebze-Kocaeli, Turkey, and published in the Journal of Food Protection (Vol. 53, No.5) in May 1990 cited 176 references to published studies, articles and papers. Fraunhofer Institute for Food Technology and Packaging (FhILV) comparative study into the effect of light on cream packed in plastics containers and lidded with foil or plastics materials. ‘Light spoils milk’ Prof. Edmund Renner, Giessen University: Comparative study by, into the effect of light on vitamin B2 content of milk packaged in foil-lined cartons v. glass. **Study commissioned by Stonyfield Farms from University of Michigan Center for Sustainable Systems, USA, 2002. ***Tetra Pak/GfK Sofema study 2002: The milk market– study into usage and attitudes.
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