Packaging of mushrooms in a humidity-regulating plastic tray for preventing water condensation

Mushrooms are highly transpiring and respiring commodities. The plastic films commonly used for fresh produce have lower water vapour permeability relative to the transpiration rate of mushrooms. Therefore, excessive moisture accumulation occurs inside the package causing condensation. Fluctuations in temperature along the supply chain aggravate the problem further. The objective of the present study was to actively control the headspace relative humidity using hygroscopic salt (NaCl) incorporated directly into the punnet matrix. Humidity regulating trays prepared with an active layer containing 18% (w/w) salt were used to pack mushrooms and the amount of water absorbed/condensed was compared with trays without salt. The headspace relative humidity in the salt containing trays was 92.7% as compared to 100% in control-PP tray. The salt containing tray absorbed 1.1 g of water vapour during first day of packaging and reached its maximum capacity after 8 days (2.2 g). This absorption capacity was far too low for the packaging of 250 g mushrooms which demanded a capacity about 5 to 10 g resulting in excessive condensation inside the humidity regulating tray. In conclusion, the humidity regulating trays have not enough capacity to absorb sufficient amount of water vapour from the package headspace containing mushrooms.