|Authors: ||G. Rux, P. Mahajan, M. Linke, S. Saengerlaub, A. Pant, O. Caleb, M. Geyer|
|Keywords: ||fresh produce, transpiration, condensation, humidity, packaging|
Most polymeric materials used in fresh-produce packaging have lower water-vapour transmission rates relative to the transpiration rate of fresh produce.
The consequences are high humidity levels and condensation of water vapour inside the package.
Humidity-regulating trays were developed and tested in this study.
They were made from a thermoformed multilayer structure consisting of polyethylene (outside), a foamed hygroscopic ionomer (active layer) with 0 or 12% (w/w) NaCl, and a hygroscopic ionomer (sealing layer, inside). These trays were used to study moisture absorption kinetics at 100% relative humidity (RH) for 16 days.
Additional trays containing 7 g water were sealed with the high barrier lidding film, and headspace RH was monitored continuously over time.
Finally, strawberries and tomatoes were used to test the performance of the humidity-regulating trays.
The amount of moisture absorbed by the tray was directly proportional to the amount of salt embedded into the tray matrix, e.g. 0 and 12 % (w/w) salt trays absorbed 7.6 and 13.2 g moisture, respectively.
The headspace RH in the trays sealed with lidding film was found to be 89.8, 99.6 and 100% in trays with 12 and 0 % (w/w) salt and control polypropylene trays, respectively.
The trays containing fresh produce were able to regulate RH below 97%, but at the expense of higher product weight loss (2-3% for strawberry, 1% for tomatoes) compared with control polypropylene trays (0.6%).
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