Enhanced mass transfer during osmotic dehydration of high pressure treated pineapple

Abstract

High pressure pretreatment (100-700 MPa) was applied to enhance mass transfer rates during osmotic dehydration of pineapples and accelerate the process. Experimentally determined diffusivity values, based on a Fickian model, increased fourfold for water and twofold for sugar. Diffusivity values were correlated with pretreatment pressure by an equation of the form D=A exp(-B/P), which suggests that diffusivity would level after an initial increase in pressure. The increase was attributed to breaking-up of cells walls which facilitated the transport of water. Evidence for the extent of cell wall break-up with applied pressure was based on differential nterference contrast microscopic examination of tissue. Preliminary experiments on rehydration characteristics showed high pressure pretreated samples did not absorb as much water as controls.