Vacuum packing: Touching the void

Lynda Searby, Packaging News, 01 October 2008

 

With new kit offering automation features and the potential to slash the amount of materials used, Lynda Searby asks if the vacuum pack is about to make a comeback.

 

The benefits of vacuum packs versus many other packaging methods are plain to see: the packs allow foods to be kept fresher for longer, are economic on material usage and require less storage space than rigid packs. They also prevent freezer burn and offer exciting potential for 'cook in the bag' convenience products.

 

However, the technology does have its downsides, and in the past this has deterred some potential users.

 

Although entirely cosmetic, one issue is that deoxidation in the vacuum causes meat to brown. UK consumers are

conditioned to believe red meat is fresh meat, and for this reason, a lot of retail meat packs are thermoformed gas-

flushed packs.

 

Similarly, as Ian Kitching, managing director of Swissvac, points out, when you open a vacuum pack of sliced cooked

meat or bacon, the meat is wet and the slices stick together, which doesn't happen when it is packed in a plastic tray with

gas flushing.

 

While machinery manufacturers are powerless to do much about such issues, there are some areas over which they have slightly more control.

 

Vacuum packing with a chamber machine, for instance, is an inherently slow process because it involves loading the product into the chamber, then waiting until the cycle has finished before unloading the packaged product. However, double chamber or 'swing over lid' machines that make table-top vacuum packaging quicker are now available.

 

"With a swing-over lid machine, while the lid is down on one side, you can load and unload the other chamber," explains Kitching. Swissvac distributes the Dutch-built Audion range of vacuum packers, which includes a swing-over lid machine.

For larger food operations, most vacuum packaging equipment manufacturers supply belt-fed chamber machines, which allow continuous packing.

 

The Food Machinery Company, for example, sells a range of machines built under licence in Taiwan, incorporating Busch vacuum pumps. One of these is the J-V022, a conveyorised system on which the chamber moves up and down over the conveyor. "This means it unloads itself and staff can continually load bags even while it's vacuuming," explains the company's Lee Gapper.

 

Increased automation

But even with continuous systems, operator intervention is still usually needed for loading the product into the vacuum bag.  According to Uriel Inauen, chief executive of Inauen Maschinen in Switzerland, reducing the manual involvement in the  process by increasing automation and better integrating vacuum packaging machines with up- and downstream equipment such as shrink tanks and dryers is what customers are asking for at present.

 

"The focus is on automating the process – in particular getting the meat into the vacuum bag and transferring

the bag with the product in on to the conveyor," says Inauen. The company's K7 machine, launched at Interpack, can be integrated within a fully automated vacuum shrink line.

 

This observation is backed up by Peter Mellon, managing director of Reiser UK, who says: "Customers are pushing to have products loaded automatically into the bag and into the machines – they want the minimum number of people on the line."

 

An Austrian-built system launched in April, Supervac's GK842, which is sold in the UK by Reiser, responds directly to this requirement with its split-belt operator mode. "This mode means a product can be brought to the machine independently of going into the chamber, so only one operator is needed.

 

With previous systems, two operators were needed to load the machine."

 

Another new addition to the machines, according to Mellon, is the ability to remove excess packaging material. "It's trimmed off and sucked out of the chamber into a bin, so the pack is nicely cut to the right size and there's no excess packaging."

 

The sealing bar on the machine is a bi-active system that seals from top to bottom. "Typically our competitors only seal from the top," says Mellon. "We can guarantee less leakages through more accurate sealing."

 

On Inauen's K7 machine, seal integrity is provided by a sealing system that originated in the medical packaging industry, where security is paramount.

 

"Sealing is temperature controlled, so users can preset the temperature according to the material they are sealing. This makes for an excellent, tight seal. The machine can even wrinkle seal, so if the bag is not exactly flat in the chamber or it is contaminated with fat or juices, it will still create a tight seal," explains Inauen.

 

Reducing cost

On the flow-wrapping front, Reiser has been acting since July as exclusive UK agent for Repak, which produces machines that feature a rapid air-forming system that enables the use of thinner films.

 

"The forming system uses high air pressure to form the pack very quickly," explains Mellon. "This results in cost savings because you can down-gauge the thickness of the material by up to 20% while maintaining the same barrier properties and thickness in package corners."

 

However, according to Ilapak sales director (HFFS) Mike Butler, the problem with using flow-wrapping systems to create vacuum packs is their speed. "The film goes round the product, it goes to the single sealing jaw area, and then just before the seal is made the vacuum is pulled. You get no more than 10, 15 packs a minute," he says.

 

With this in mind, Ilapak has launched a machine which it describes as a 'hybrid', combining the best characteristics of a flow wrapper and a thermoformer.

 

Butler says the Delta VacMap offers all the cost-saving and efficiency benefits of conventional flow wrapping, such as

high throughputs, fast product changes, ease of use, reduced material and labour costs, fully automatic feeding and high quality pack presentation, while achieving a comparable shelf life to thermoforming.

 

It achieves this by relying on a combination of vacuum and MAP (modified atmosphere packing) technology within a single machine. An inline vacuum feature allows the system to extract trapped pockets of oxygen found inside the product itself, particularly spongy bakery products, to keep the product fresher for longer than a standard MAP flow wrapper.

 

"The product comes in on a belt and there is a series of chambers going round like a carousel. The chambers close down over the product and evacuate, then the gas is flushed in when the vacuum shuts off," says Butler.

 

Ilapak has calculated that each VacMap machine can achieve up to 50% more throughput than a typical thermoforming machine. The VacMap is already up and running on pizza lines in France and Germany.

 

As food manufacturers and packers tighten their belts, and vacuum packaging equipment designers make kit quicker, easier to integrate inline and more economical on packaging material, could we be about to see a resurgence in the popularity of the vacuum pack?