Convenience food is enjoying continuing popularity and currently recording two-figure growth rates in the market. As consumers demand fresher goods, food processors are creating more refrigerated, ready-to-serve products that are easy to prepare and have a high quality taste.
To retain freshness and extend shelf-life as far as possible, refrigeration is not enough, and these products require packaging with a modified atmosphere.
This involves evacuating the pack, filling it with a special protective gas mixture of nitrogen and carbon dioxide and then closing it with an airtight seal. This limits the multiplication of germs in the pack, and preserves taste and quality for considerably longer. However, many products require individually developed solutions that go beyond the standard.
One-way pressure release
Freshly-rolled yeast dough for pizza is one example of this type of product. Yeast dough gives off CO2 when it ferments, but protective gas packages have an airtight seal. This means that the packaging ‘balloons’ and the customer mistakenly concludes that the product is spoiled.
To avoid this, the pack must release the excess CO2, but should not let in any oxygen from the atmosphere if sinking temperatures lead to a drop in pressure — i.e. it needs a one-way valve. The challenge is to find a technically and economically viable way to integrate a one-way valve into the packaging.
The solution is available in a special Multivac R 530 thermoformer. Thanks to the enormous range of construction options, the machine can be adapted to the individual needs of the customer.
Applying a valve
For this unusual precision process, the upper web is scored in a cross-shape in eight places. The valve sealer carriage then moves over the upper web, positioning a valve above each of the cross-shaped slits. Valves are sealed firmly to the upper web, completely covering the score marks.
The machine has already used heat and pressure to thermoform eight packing moulds from a lower web, and the packing moulds are hygienically filled from above at the loading section. The upper web is then positioned over the lower web providing one valve in each pack, and sealed together at the long sides — this allows gas flushing from the sides, which are still open. The packs are then evacuated, filled with protective gas, and finally sealed and separated.
This process provides a reliable technical solution to the problem of ‘ballooning’ packages. The one-way valve in each pack lets excess CO2 escape through the slit while maintaining an absolutely airtight seal with the upper film. The valve is discretely placed on the underside of the film so as not to attract attention. Gas flushing removes the oxygen stored in the rolls of dough from the packaging, leaving precisely the desired gas mixture inside.
Proven in practice
Despite the array of technically complex individual steps, the machine produces the large format valve packs with a very high cyclic performance, and thus functions economically. To achieve this, there is exacting quality assurance for the fully automatic procedure at several points: sensors check the valve and the pack contents are in the correct position, faulty packs are automatically sorted off onto the exit conveyor belt. A detector also finds packs, where the rolls of dough have been contaminated by metal during production.
The solution, developed by Multivac, proved itself in practice over a year of testing at Swiss Nestlé subsidiary, Leisi. This special machine now runs around the clock in three shifts, only stopping to change film or for maintenance. This year, Nestlé has brought in another R 530 with valve application device to extend production. This is where some further developments come in, such as modern IPC controls. The design has also changed slightly: the side sheets were removed for the length of the loading section, to give staff more room to move during filling.
Mirrored lines, padded packages
The Dutch bakery chain Bakkersland specialises in ready-made baked goods — manufactured from a wide range of dough and in a variety of sizes, from mini-rolls to baguettes. Here the quality of the packaging matters as the baked goods have to retain their quality until they reach the ovens of the consummers, requiring absolutely impermeable packaging with an extremely low residual oxygen content. Bakkersland also relies on the thermoforming machines by Multivac with six machines of type R 530 currently in use.
Multivac has coordinated the machines with each other in a special way, with all operational elements of the second line installed as a mirror image to the first line — such as the controls, film intake, etc. In this way the machine operator can keep both lines in view from the centre path between the packaging machines and complete all necessary tasks without first having to walk around the machines — creating a great increase in work efficiency.
The R 530 machines installed at Bakkersland reach an output of eight to ten cycles per minute. The product output depends on the size of the baked goods. For example, every hour the machines package up to 25,000 small rolls or 5,000 baguettes. The pre-baked products are guided to the lines directly after cooling off and are then automatically placed into the thermoformed packages. The packages are thensealed in a modified atmosphere, where a slight ‘balloon’ effect is accomplished: This padding protects the products from pressure and bumps.
The Multivac machines achieve a residual oxygen level of less than 0.2%. Together with the strong, tightly sealed seam, this offers the guarantee for a long shelf-life for the products. At Bakkersland, a seal testing station is also installed, which can detect and sort out the rare cases of leakage, thus minimizing sales rejects.
Special solutions are the norm
Creative packaging solutions are often not just functionally necessary. In the booming convenience market, product presentation at the point of sale plays a decisive role — an increasing amount depends on attractive packaging shape and design. This means that different products need different solutions.
This is why adapting industrial machines to individual customer requirements is the norm at Multivac.
According to Multivac Sales Manager, Dr Matthias Ehrat, “Multivac has been making thermoformers for challenging packaging for about 40 years, and we have become experts at configuring and installing complex machines.
“We work with our customers to produce solutions that find a way to carry out special packing tasks. The results are often bespoke products, precisely tailored to the application.”
Multivac’s new generation is among the prize winners of this year’s iF Packaging Award, awarded by renowned iF Industrie Forum Design. The award recognizes successful integration of innovative design with reliability, functionality, ergonomics and processing.