Vacuum and Gas Flushing Machines

Vacuum Skin Packaging Machines

The principle of the vacuum skin packaging system utilizes a top and base web of material. However, it differs from the vacuum thermoforming machine in that no forming dyes are required. The product is placed on the lower web which may be left flat or formed to suit the product if desired, before being indexed into the chamber of the machine. The top web, which has been preheated to improve its flexibility, is draped over the cheese portions utilizing the product as the dye and using minimum pressure. The air is removed by vacuum and the product is fully encased in a protective second skin before heat sealing the top and bottom webs.

Gas Flushing Machines

This kind of packaging machines is also known as “Modified Atmospheric Pack”, and the machine uses two reels for packing the cheese as described in the form-fill-seal. After evacuating the air from the vacuum chamber, it is then replaced by a controlled mixture of gas (carbon dioxide, nitrogen or a combination of these). Thus this system is referred to as gas-flushing. Thus this system prevents the spoilage of cheese during intermediate storage prior to retailing.

In practice carbon dioxide is widely used, compared with nitrogen as gas flushing unit, because it reacts with the moisture in the cheese to producer carbonic acid and so gives the product a neat snug appearance similar to a vacuum pack. Carbonic acid further serves as a mould inhibitor.

VACUUM PACKAGING MACHINES

PACKAGING MACHINES

There are three different types of packaging machine which can be used for packaging portions of cheese. Some examples are given below

Chamber machines

This type of equipment uses mainly pre-made pouches (e.g. nylon/polyethylene laminate and polyester or cellulose/polyethylene laminate or related plastic films). The pouch is filled with product, loaded into the chamber which evacuates the air from the pack and then heat seals it.

As a result, the product is in air tight container and the shelf life of cheese packaged in this system (kept under refrigeration) is up to 3 months. In small operations, this system of packaging is carried out manually by placing the portion of cheese inside the pouch and transferring it to the vacuum chamber. When the lid of the chamber is closed, the vacuum is activate followed by heat sealing.

Automatic thermoforming machines

The majority of high speed, vacuum packaging machines are known as form-fill-seal machines. Most of these machines have been adopted for gas flushing. The packaging material is delivered to the dairy in large reels of plastic sheet and two reels are fed into the machine. The base reel which is a thermoplastic material is warmed and vacuum or compressed air stretches the film into cooled, multi-row moulds, which transforms the sheet into desired shape.

The cheese portions are placed into the well and as the cheese container moves forward to the vacuum and heat sealing chamber, it is covered by a plastic sheet from the top reel. The following stage consist of removing the air from the chamber, heat sealing the thermoplastic material to each other, and finally longitudinal and cross cutting units separate the cheese portions before transferring them to the weighing and labeling section.