Osmotic Dehydration of Coconut Pieces: Influence of Vacuum Pressure Pretreatment on Mass Transfer and Physical Characteristics

Abstract

The effects of vacuum pressure pretreatment on the osmotic dehydration of coconut pieces and on mass transfer parameters were studied and some physical characteristics were evaluated. The coconut pieces were immersed in sucrose solution (60% (w/w)) for 8 hr at room temperature. Samples were subjected to vacuum pressure at 50 and 65 mbar with different pretreatments: 1) vacuum pressure for 20 min, then atmospheric pressure and 2) vacuum pressure for 10 min, atmospheric pressure for 10 min, vacuum for 10 min, then atmospheric pressure. The results indicated that there was an interaction effect between the vacuum pressure levels and vacuum pretreatments on solid gain (P < 0.05) while the main effects of those two factors were found on water loss (P < 0.05). The vacuum pretreatment affected weight reduction (P < 0.05). The sample pretreated with 50 mbar had lower whiteness than the sample treated at atmospheric pressure (P < 0.05). The vacuum pressure pretreated sample had lower firmness and a lower cell disintegration index than the nonpretreated sample (P < 0.05). Microscopic observations revealed the integrity of the cellular matrix associated with mass transport behavior and mechanical properties.