Feature Packaging Machinery Putting new techniques on the MAP
In this article Mark Sumnall of Busch takes a closer look at modified atmosphere packaging (MAP) - a process that is utilised in food processing and medical instrument manufacture - and how it is used with centralised vacuum systems
T
he MAP process is created by evac- uating some or all of the air within a container, such as a meat tray or cheese packaging, and replacing it with a protective gas mixture - this is known as ‘gas flushing’. The pack is then hermetically sealed with a film preventing the modified atmosphere from escaping and unwanted air getting back inside. MAP can be used with a wide range of vacuum from 500 millibar down to one millibar, and how it is applied will depend on the needs of the manufacturer and the process. MAP has made a significant contribu- tion to the food sector by providing longer shelf life, while maintaining qual- ity, appearance, freshness and flavour. The gases inhibit the reproduction of micro-organisms, reduce oxidisation, protect dry products from moisture and delicate items from becoming crushed. With medical applications, MAP main- tains sterilisation and protection of the product and for more general goods, it gives protection against external envi- ronmental influences.
Gases Basic MAP gases include Oxygen (O2 ),
which is used in both the lowest (<0.2%) and highest possible concentration (>60%) to inhibit the growth of aerobic micro-organisms and so increases the shelf life of the product, retains the nat- ural colour of red meats and maintains respiration of fruit and vegetables. Nitrogen (N2
) stabilises the gas and main-
tains pack volume, thereby preventing it from collapsing, and this contributes to the protection of the packaging. Carbon dioxide (CO2
) reacts with
water to form carbonic acid, which helps to keep pH levels to a minimum. This atmosphere inhibits growth of micro-organisims, bacteria and mould. Normally, the higher the CO2
level, the
longer the shelf life, but using excess levels can taint flavour, cause drip loss and package collapse.
More unusual MAP gases include Argon (which is inert and has the same properties as Nitrogen), and Carbon Monoxide (which is colourless, odour- less and flammable, and is used to
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Right: a food processing
centralised vacuum system featuring the Busch R 5 rotary vane vacuum pump, along with pipe work and control panel
increase shelf life while reducing differ- ent spoilage and pathogenic bacteria). Also included is Ozone which is an unstable form of Oxygen and offers oxi- dising and disinfecting properties used in food preservation.
Varying methods
The actual MAP packaging process uses different methods to deliver different end results depending on requirements. Thermoforming is where vacuum is used to help form heated plastic to make a shaped container to hold the product, with single or multiple compartment trays being produced by this process. Once the product has been placed inside, it is then sealed using plastic film. Vacuum shrink wrapping also uses the MAP technique and can be carried out using either a vertical or horizontal packing system.
Right: central vacuum systems reduce heat
emissions and the pumps are controlled by process demand, running when needed and being turned off when demand drops, thus reducing energy usage
needed adding further heat and noise, and environmental legislation requires the eradication of oil mist contamination. The answer to all these issues is to relo- cate the pumps in a separate plant room and have the required vacuum supplied via pipework and control systems. As many packing machines are sup- plied with oversized pumps, central vacuum systems offer the advantage of reduced energy costs due to lower installed power, as the well designed system looks at overall vacuum require- ments, often reducing installed power by 20-30%, depending on requirements. These systems reduce heat emissions and the pumps are controlled by process demand, running when needed and being turned off when demand drops, thus reducing energy usage. In addition, as pumps run when required rather than continuously, pumps wear less, fewer parts and repairs are needed, maintenance is reduced with lower lubricant con- sumption and reduced waste oil dis- posal. Integration of standby pumps and the potential to add pumps to a well designed system allows produc- tion time to be maximised.
Summary
Nowadays, with so much focus on LEAN manufacturing methods and streamlining of processing, many engi- neering managers are installing cen- tralised vacuum systems. Traditional vacuum solutions have incorporated stand alone pump(s) which would be mounted alongside or within the pack- ing machine to provide the vacuum. Pumps increase noise levels as well as generating unwanted heat in production areas and require additional air condi- tioning to maintain safe working temper- atures - particularly in chilled packing/storage work areas. If produc- tion capacity increases, more pumps are
Use of MAP and centralised vacuum systems can offer many benefits for the manufacturer and in turn the consumer. As with any complex and technical equipment, there is much to think about when designing a new system or updat- ing or expanding an existing installa- tion, and getting everything right at the outset is vital to ensure a smooth run- ning project that delivers the best solu- tion. Working with the manufacturers and drawing upon their knowledge, expertise and experience will ulti- mately provide the best result all round.
Busch
www.busch.co.uk T: 01952 677 432
Enter 209 SEPTEMBER 2013 Automation
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