Osmotic Dehydration of Pineapple

Osmotic dehydration is one of the novel drying technique. The principle used in this process is that water diffuses from dilute solution to the concentrated solution (Hypertonic solution) through a semi-permeable membrane until concentration equlibrium is reached. The technique can be use to remove water from cellular metrials such as fruits and vegetables. The cell membrane of these materials is semi-permeable in nature and is more selective for water and acid than solute.

In the present study, ripened pineapple (Anannas comosus) was used. The fruit was cut into slices of 1.5 cm approximately weighing exactly 10 g each. The slices were osmosed in 40%, 50%, 60% concentrated sugar syrup at temperature of RT, 50oC, 60oC, and 70oC with a sample to solution ratio of 1:6. Observations on solid gain and water loss were recorded. Initially the pineapple samples were osmosed for 5 hours at varying temperatures and they were further dried at 70oC in vacuum to 5% m.c. The osmodried samples were tested for total and reducing sugar content and the rehydration ratio was also estimated.

The water loss and solid gain was found to increase with an increase in temperature (from RT to 70oCs and concentration (from 40% to 60%) linearly. The maximum water loss was found to be 37.44% and the corresponding value of solid gain was found to be 30.30%, when dehydrated in 60% sugar syrup at 70oC with 1:6 fruit to syrup ratio.

The highest rehydration ratio of 1.602 was found. The maximum total and reducing sugar content of osmo-vacuum dried samples were found to be 17.432 and 6.6% respectively.

Source: Invention Intelligence, May - June 2006