Osmotic dehydration of strawberry halves: influence of osmotic agents and pretreatment methods on mass transfer and product characteristics

The impact of different pretreatment methods [high pressure (HP), high-intensity electric field pulses and freezing], osmotic solutions (sucrose, glucose and salt-sucrose mix) and osmotic conditions (atmospheric pressure, vacuum and ultrasound treatment) on the mass transfer of strawberry halves during osmotic dehydration (OD) and on some physical characteristics (leaching of cell constituents, colour and texture), were investigated. Highest water loss was obtained in samples treated under vacuum, in a salt-sucrose mix or under HP or in a high-intensity electric field. The increase in solid gain relative to untreated samples was 96-270% for the prefrozen treatment, 40-160% for high pressure and 50-62% for high-intensity electric field treatments. OD under vacuum and the use of glucose solutions facilitated greater solid gain. Leaching of cell constituents was high in prefrozen samples, leading to greater change in product colour and softer texture compared with other pretreatments. Although OD under ultrasound treatment enhanced mass transfer, its overall influence was not significant (P > 0.05) compared with atmospheric pressure.