studied the effect of different pretreatments
(i.e. dipping in alkaline emulsion of ethyl oleate or in hot
water) on moisture diffusivity of seedless grapes. They showed that
both pretreatments activated the diffusion process by reducing the
skin resistance to water transfer at the beginning of the process. The
ethyl oleate pretreatment was found much more efficient by maintaining
higher internal diffusivities at the end of the drying process.
Moreover, the increase in mass transfer coefficients at different
temperatures for the ethyl oletate pretreated samples was two times
that for the hot water pretreated samples during the drying.