Enjoy high-quality products: Health-conscious consumers continue reaching for bio meat, fish from sustainable sources, selected fine pâtés, or ready meals made from natural ingredients. For several years now, food manufacturers and the retail sector have increased their use of vacuum skin packs, allowing these foods to be more attractively packaged and have the maximum possible shelf life.
This process involves the upper web of the pack being draped without tension over the product like a second skin so that it is not deformed and retains its natural appearance. Even products with sharp or hard features, such as bones or shells, can be packed securely and reliably with this process. The vacuum in the pack contributes to an extended shelf life for the product. Since the upper web is sealed to the entire surface of the lower web or tray, liquid is also prevented from leaching out of the product. The food is fixed firmly to the base of the pack or tray so that it can not slide around, and it can be presented at the point of sale as either a stand-up pack, a hanging pack or a conventional horizontal pack. If vacuum skin packs are stored in the freezer, they also provide reliable protection against freezer burn.
The vacuum skin process is not only suitable for harder and more stable products such as steaks, sausages, cheese or frozen foods, it can also be used for soft foods like fish, pâté or thin fillets.
Vacuum skin packs offer food manufacturers a wide range of possible applications. As a long-standing partner of the food industry, MULTIVAC has used its many years of experience in vacuum skin packaging to offer a very comprehensive range with MultiFresh™. In addition to thermoforming packaging machines, MULTIVAC also offers solutions for producing vacuum skin packs on traysealers.
While standard trays with sufficient dimensions are used on traysealers, MultiFresh™ thermoformed packs are more flexible in their design, since both the lower web and upper web are run on the machine from a roll of film. This means, for example, packs can be produced with individually formed contours or other features. Thermoformed packs can also be provided with an easy-open corner so the consumer can open them easily. The base of the pack can also be designed to the customer’s individual requirements, for example with ribbing, special radii, base embossing or other design features, which are intended to provide rigidity to the pack or enhance the external appearance or brand awareness.
The pack cavity of MultiFresh™ thermoformed packs is typically 5 - 10 mm deep, and the product protrudes above the pack cavity, allowing it to be presented very attractively. The pack cavities are thermoformed
and then filled either manually or automatically, following which the packs are then sealed under vacuum over the entire surface in the MultiFresh™ sealing die. Cutting units then give the pack the desired contours and finished pack shape. The integrated upper web chain guidance on MultiFresh™ thermoforming packaging machines ensures that the upper web is firmly guided right into the sealing station. “The upper web chain guidance holds the film on the right and left sides like a rescue safety net, which is pulled in all four directions. This means that the film remains permanently under tension across the machine running direction. This procedure ensures there is a high level of process reliability, while delivering very high pack quality irrespective of the machine speed”,says Thomas Fickler, Product Manager for skin packs at MULTIVAC.
The MultiFresh™ machine range meets all the requirements of pack size, output and level of automation. The standard program includes the R 175, R 275 and R 575 thermoforming packaging machines, the semi-automatic T 200 and T 250 traysealers, as well as the fully automatic T 300, T 600, T 700, T 800 and T 850 traysealers. Thanks to the simple die change, all the machines can quickly be converted for different pack sizes and shapes.
MULTIVAC has recently expanded its standard range with the R 105 MF entry-level model, which is designed for the economical production of high-quality vacuum skin packs in small and medium-sized batches. The machine has been equipped with heating and chain guidance for the upper web. The integrated upper web chain guidance ensures that the film is firmly guided right into the sealing station. There, the film is heated up once more before being draped, without creases, over the product and sealed to the entire surface of the lower web. The R 105 MF has the same technical equipment as the large machine models, making it possible even for small-scale manufacturers to start using vacuum skin packs.
MULTIVAC also offers a packaging solution for packing high products of up to 120 mm. For this, MULTIVAC equips the MultiFresh™ thermoforming packaging machine with an additional upper web forming station. The R 575 MF PRO forms the upper web before it is transported into the sealing die. The thermoformed film is heated once again in the dome of the sealing die, before being draped over the product. This innovative procedure ensures that in the sealing die the upper web already has the shape of the product that is to be packed. The additional heating makes the film sufficiently elastic, so that it can cling around the product tightly and without creases. Thanks to the special upper web forming station, packs can be produced with a product protrusion of up to 90 mm.
Vacuum skin packs with high product protrusion can also be produced on traysealers with Tray MultiFresh™ PRO. For this, the T 800 is equipped with a die in which packs with a product protrusion of up to 100 mm can be run. A die change with the mobile die trolley can be carried out just as quickly as previously. This means that other packs can also be produced on the T 800 without additional work to convert the pack. Existing machines can be retrofitted without problems for this application, without the footprint of the machine or line being increased.
Vacuum skin packs only unfold their full potential however, if the upper and lower web materials are ideally matched to the packaging machine and the product. In cooperation with several film manufacturers, MULTIVAC has put together its own film range for producing vacuum skin packs, which is marketed under the brand name of MultiFresh™. When selecting and approving the upper webs, the following criteria were among those taken into consideration:
The criteria for the approval of the lower webs included their barrier properties, the availability of different sealing systems, skin peel and tear peel, as well as their thermal properties (e.g. films for high-temperature applications). The films also had to be available in various colours and capable of being printed.
As part of the approval process, the materials were also thoroughly tested on MultiFresh™ packaging machines. “The series of tests were based on standardised procedures in which we extensively tested both the functional and visual properties of the films”, says Thomas Fickler, Product Manager for skin applications atMULTIVAC.
The tests were designed to answer the following questions: What is the stretch and shrink behaviour of the film? Does it drape cleanly over the edges of the product? Does it enclose the bottom of the product precisely? How does it behave during the sealing process: are creases formed, can the packs be opened easily? What influence does the pack have on the shelf life of the product?
When carrying out these series of tests, MULTIVAC was able to draw on its extensive know-how in vacuum skin packaging technology: the company has the largest machine portfolio in the market and was one of the first manufacturers to offer thermoforming packaging machines for producing vacuum skin packs. MULTIVAC is also characterised by its many years of application expertise in food packaging.The upper and lower webs approved by MULTIVAC combine functional benefits with outstanding visual properties. They provide a high level of pack quality and an attractive product presentation. The materials can be run on MULTIVAC packaging machines without machine parameters having to be altered. All MultiFresh™ films comply with the current requirements and regulations for the food processing industry.“We have trust in the experience and innovation leadership of the film manufacturers, that our MultiFresh™ film range will continue to be further developed”, says Thomas Fickler. “The high level of expertise in the advice given by MULTIVAC staff also ensures our customers receive the optimum system for their products. Customers can test various packaging solutions and materials with their own products in our Training & Innovation Center in Wolfertschwenden”.
The skin upper webs are available in various thicknesses and have been designed for different product shapes and heights. This means it is possible to pack products that have flat, medium-high or high profiles, as well as food with irregular contours. The possible applications range from flat pieces of meat to dry products such as sausages or pieces of cheese. Other special applications, such as fresh fish that may have to be packed in films with low barrier, can be produced with the MultiFresh™ film range. It is also possible to pack products with high protrusion or sharp edges in MultiFresh™ with a high level of quality and reliability.Thanks to the high quality of the film material, users can utilise thinner films overall than may be the case with some competitors, meaning the packaging volume can be reduced significantly.
The MultiFresh™ range of lower web products is comprised of APET and PS composites and covers a wide spectrum in terms of its mechanical and barrier properties, along with different peel systems. In order to make the packs distinctive, MultiFresh™ lower webs are also available in different colours as well as in metallised versions.Both the upper and lower webs can be printed. It is also possible to apply decorative, price or promotional labels to the packs, as well as printing variable product and production data that can be changed manually or automatically.