The durability of press-formed paperboard trays – Effects of sealing and drying

Abstract

Dimensional measurements were recorded to observe the durability of press-formed paperboard trays used for food processing via heating and cooling of the paperboard trays containing oatmeal. A set of the studied press-formed paperboard trays were dried before being heated, and a set of the paperboard trays were heat-sealed before being cooled to compare the effects of drying and sealing on the durability of the tray. In addition, empty trays were heated to observe the impact of food processing conditions on its durability via leak tests with a colouring solution as well as optical analysis of the material coating on the surface of the trays. The drying process of the trays was observed to improve the dimensional stability of the trays while being heated, and heat-sealing the trays yielded a major positive impact on the dimensional stability of the trays while being cooled. The leak tests and optical analysis results on the heated empty trays showed a negative durability impact from the food processing conditions. It was concluded that adjusting the heat-sealing parameters and food processing conditions is necessary in order to achieve improved durability of the press-formed paperboard trays for food processing purposes.

A folding method to increase the rigidity of paperboard tray packages

“…The measured moisture content of the trays was 7.5% after the storing tests, which was greater than the 6.3% recorded before the trays were stored. Consistent with the previous work (Niini et al 2021), the material response to the moisture absorption was observed as a flange distortion on the longer sides of the tray (Figs. 12 and 13).…”

“…Humidity exposure can lead to stiffness degradation and dimensional instability of paperboard, limiting the use of paperboard trays in moist environments typical to the production and storing of food packages. The drying and heat-sealing of paperboard trays improved the dimensional stability in a previous work (Niini et al 2021), yet the negative humidity effect to the tray rigidity was not eliminated. The humidity exposure yields creep deformation in tray packages, and cyclic humidity conditions aggravate the creep (Sørensen and Hoffmann 2004).…”

“…The SEM images showed similar microscale characteristics of PET between the folded and the reference trays. In a previous work (Niini et al 2021) the prolonged exposure of the PET coating to temperatures above 140 °C was connected to the noticeable crystalline growth on the surface topography. The folding of the trays at 90 °C or below showed no major effect on the crystalline growth on the PET coating as the optical quality of the folded trays and the reference trays was similar.…”

“…Moreover, the rigidity and quality of paperboard tray packages is connected to the shaping of the tray flange and bottom during the 3D forming process (Tanninen et al 2018). Achieving and sustaining a sufficient rigidity with the paperboard trays is especially important in the demanding environment of food packaging applications (Niini et al 2021).…”