Molded Fiber Paper Trays

Molded fiber trays are made from 100% recycled paper, specifically designed for packing fruit and protecting it during the packing, storage and shipping process. They are made with special characteristics that allow them to be used in different temperatures, moistures and humidity environments without losing their ability to protect and handle the fruit.

Evolution of the Molded Fiber Paper Tray

Early in the 20th Century, most apples were packed and shipped to the market place in slatted wooded boxes. Michelsen Packaging Company sold the wooden components for making slatted boxes. This business evolved into nailing together the components in our warehouse and selling them as made-up boxes. A lid was nailed to the wooden “shook” crate to contain the loose packed apples in shipment. The saying in those days was “nail the lid until the juice flies,” which lead to our focus in apple immobilization.

Approximately mid-century, a German engineer designed a tray made from molded paper fiber. This tray separated each apple with specific size cups, provided a cushioning effect, was breathable (allowed gas transfer), and was recyclable. These trays also had a hygroscopic aspect which could absorb moisture from the apples and surrounding atmosphere, thus becoming pliable and allowing more tray to cover the surface area of each apple (trays conformed to the fruit shape). An advisor for this project was Dave Clevenger, a Michelsen sales representative. Two Companies, Friday and Mapes became the USA manufacturer of these paper trays.

The design feature of the trays allowed the apple packing industry to utilize a paper shipping container (corrugated box) that was far more cost effective than the wooded shook boxes. The apples were separated with specific size cups, cushioned from top to bottom and distributed the downward apple weight inside the box over a greater surface area and “spread the load” because of the hammock effect of the tray bridge (underneath side). In an effort to patent the tray design, the engineer had to reword the patent to bypass a patent for the bridge of eye glasses. A patent was granted. The competing tray manufacture added a feature across the tray bridge call a “hinge” to be able to include a bridge and gain a patent.

The two original tray makers changed ownership to Keyes Fiber, offering the Spring Cushion Tray and Packaging Corporation of America’s FruitMaster Tray. Michelsen Packaging Company distributed both trays.

In an effort to further protect each apple, a molded pulp cell tray was introduced to the apple packers. By inverting one tray over the other, each apple was enclosed in its own cell. The weight of apples was supported by “stacking posts” or peg-type supports. This style of pack with one apple directly on top of another created a problem with “transfer bruising.”

Once the apple industry grew accustomed to using corrugated boxes, a cell pack was developed to transport the more fragile apple, like golden delicious. The corrugated box had inner packaging of corrugated pads and corrugated partitions which were assembled by a machine at Michelsen Wenatchee. The material cost of this package was quite high.

Foam trays made from polystyrene are available to apple packers to compete against the corrugated cell packaging. The foam tray cell pack design is established by inverting one tray on top of another to protect golden delicious apples. The concept assures that each apple is protected by an individual cell. Because this design is a “stack pack,” pressure from the weight of apples stacked directly on top of one another is transferred from one apple to the one above, causing transfer bruising. Polystyrene foam trays can be light sensitive and may become brittle over time. Because the foam material is closed cell, gas transfer may become an issue. An apple is a living organism which takes in oxygen and gives off carbon dioxide (respiration). Over a long storage time, the closed cell material can block the intake of oxygen and not allow the C02 to escape. This can lead to internal breakdown within the apple. Also, the foam trays are more of a challenge to recycle and are a landfill issue.

Similar issues exist with the polystyrene foam tray pack design as with the cell pack design. What MPC termed “pressure point bruising” is created partly because the tray pack design bridge does not support the apples downward pressure weight, thereby causing apple bruises on the lower part of the cup area. The apples are resting on each other. A second issue is under the apples’ weight, the foam material collapses, pressing apple against apple. One way to view this apple damage is to turn a packed apple box upside down, pull the bottom up away from the lid (the bottom tray is now on top) and look for bruising created by the pressure points.

The molded pulp apple tray has evolved to require a high standard of quality. Automatic dispensing of trays (denesters) added onto an apple packing line demands a strong and flat tray. Trays that are fragile can create problems for apple packers with extra packing line down-time, damaged fruit and unhappy customers.