In-pack pasteurising

Some soft drinks and juices need to be heat-treated to provide a microbiologically stable product. One method considered very reliable and robust is in-pack pasteurising (IPP). This is particularly suitable for heating carbonated products as they cannot be hot-filled. Whether still or carbonated, it is normal to fill the products cold, although some still juices are heat-treated fust, filled warm and then in-pack pasteurised as this allows for a different temperature regime in the IPP cycle as well as giving a better balance of internal/external pressures during and after the IPP treatment. This method is suitable for certain plastic containers and metal cans. 

Once filled and capped, the bottles (or packs) are taken through an IPP unit, which warms them up to the pasteurising temperature (in about 20 min), holds them at that temperature for the required period (normally 20 min at 70-75°C) then cools them down. The whole cycle takes about 60 min. The actual pasteurising temperature and time cycle will be determined by the drinks technologists. 

The packaging materials (including heat-shrink sleeves, if pre-decorated, and the printing on cans) are all subjected to continual dowsing in water, warm then hot then cold, over a long period of time. Care thus needs to be taken, and materials tested, when selecting the appropriate packaging format. 

For still products there is a wider choice of materials, all of which must be resistant to heat and high humidity. For carbonated products the package must 

Care should be taken in selecting the appropriate cap-sealing compound specification and even the thread-finish profile as these will have a part to play in giving consistent performance. When selecting these components it is sensible to discuss performance requirements with the packaging suppliers. 

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Non-carbonated RTD beverages have shown some considerable growth in recent years mainly because of the availability of aseptic packaging forms. Still drinks that rely on chemical preservation or hot-pack/in-pack pasteurisation suffer from a number of potential problems, including rapid flavour and colour deterioration. 

In-pack pasteurisation. In-pack pasteurisation is normally reserved for dilutable products that are made without preservatives. Unless there are particular circumstances that demand a preservative-free product (e.g. manufacture of a certified organic product), preservatives should always be used in dilutables because of the way the drinks are used and stored. A dilutable without preservatives is very vulnerable to microbial contamination, which can lead to fermentation and possibly bottle bursting. Dilutables without preservative must be labelled to encourage refrigerated storage and short shelf life. 

In-pack pasteurisation normally demands very large and expensive tunnel pasteurisers which have several stages. Bottles are introduced into a pre-heating stage, typically around 40°C, to reduce thermal shock, and then into the pasteurisation zone, which will normally be at 70°C, for some 20 min. Following this are two hydro-cooling zones. The first of these reduces product temperature to around 40°C the second, to ambient temperature. Recovery of heat is essential to an economically viable operation. 

For all other fruit juice and nectar products either frozen storage or in-pack pasteurisation will be used, although some manufacturers who employ a hot fill process. 

In-pack pasteurisation is often regarded as a foolproof operation, although product integrity will ultimately rely on the seal provided by the pack closure. 

In-pack pasteurisation can be achieved at very low cost by simply immersing bottled product, with closures tightly applied, in tanks of heated water. A pre-heat tank at around 40°C should be employed to minimise thermal shock to the containers, and the main pasteurising tank will be held at around 70°C. A single... 

Glass bottles will normally be pasteurised using either the hot fill method or in-pack pasteurisation. 

A special case of in-pack pasteurisation is a retortable process in which the packs can be treated to elevated (above 100°C) temperatures in a retort and cooled. 

Even at this low alcohol level microbiological spoilage is a hazard. Suggested manufacturing processes are benzoic acid preservation with either sterile filtration or flash-pasteurisation of the syrup, or in-pack pasteurisation. 

Aluminium cans offer the opportunity for in-pack pasteurisation as in the case of beers. They lack headspace compared with glass bottles. This is an advantage in removing the need to consider antioxidants such as ascorbate or sulphur dioxide to combat the presence of the extremely deleterious traces of oxygen. 

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