The humidity-regulating tray showed higher condensation on
the inner wall than control-PP tray at the end of the storage period.
This higher condensation could be due to: (a) the lower RH inside
the package which creates a higher water vapour pressure deficit,
thereby increasing transpiration rate/moisture loss of produce
(Caleb et al., 2013b; Ngcobo et al., 2013); and/or (b) the effect of
condensed water vapour with salt particles on the surface of tray
thereby increasing the salinity of condensed water and reducing
moisture absorption rate of the tray. Condensation occurs when
temperature of the surface falls below the dew-point temperature
of the air within the package headspace. Anti-condensation
films
commonly used by the industry help to decrease the surface
tension of the water droplets that form on the
film’s surface. This
reduces the contact angle of the water molecules, and the water is
able to spread out more creating a more uniform layer of water,
thus only transforming visible water droplets into invisible water
layer. This helps to improve the transparency of the
film surface but
not completely eliminating condensation. Moreover, mushrooms
continue to produce moisture even at 100% RH, thus there are
equal number of molecules evaporating from the mushroom
surface as there are condensing back into the package headspace.
Thus, the amount of condensed water inside the package
headspace increases over the storage period. The morphology of
the outer tissue structure and also phenomena of super-saturation
needs to be further explored in order to explain the condensation
behaviour in fresh produce packaging.