The Influence of Blanching on Mass Transfer Characteristics during Osmotic Dehydration of Bilimbi Fruit

The effect of preprocessing like blanching was studied in comparison to non-blanching treatment to obtain mass transfer characteristics during osmotic dehydration of bilimbi fruit in sucrose solution system. Half-ripe bilimbi fruits were selected for investigation. The raw materials were separated into two groups: blanched and unblanched ones. Blanching treatment was carried out in boling water for 1 min. The two groups were then immersed in 70 ◦brix sucrose solution at ambient temperature {30± 3 ◦C) for 3000 min Without stirring. The ratio of raw materials to solut1on was 2:1. pH was Initially adjusted to 3.5. Samples for both solid and liquid phase were taken at different period in order to determine water loss, solid gain, ac1d loss, corresponding diffusivities. as well as shrinkage. It was found that blanching in boiling water for 1 min not only led to higher rate of water loss, soluble solid gain, and acid loss but also higher rate of shrinkage of the raw materials in comparison to those of non-blanching treatment. Apparent diffusivities for water, soluble solid and acid were found h1gher for the blanched materials. It was summarized that preprocessing like blanching should be carried out before the dehydration process in order to soften the fruit texture for better diftus1on. nevertheless fruit shrinkage or volume reduction should be Improved.