Mass Transfer Kinetics of Carrot Slices During Osmo-convective Dehydration & Its Qualitative Evaluation

Abstract

The present study was carried out to investigate the mass transfer kinetics of carrot slices during osmo-convective dehydration and its quality evaluation. The effect of temperature and osmotic solution concentration ' on solid gain and moisture loss and drying characteristics of carrot (osmosed as well as control sample) were studied. Quality evaluation of osmo-convective dried carrot slices were also carried out with respect to I rehydration ratio, color and sensory characteristics. The moisture loss and solid gain increased with increase in salt and sugar concentration and temperature. The moisture loss by carrot slices increased non-linearly with increase in duration of osmosis, solution concentrations and temperature and mass transfer was faster in initial period of osmosis than the later period. Maximum moisture loss was obtained at 60°C for osmotically dehydrated carrot of 60% sugar and 3% salt concentration and the it ranged from 13.32% to 56.93%. Solid gain increased with duration of osmosis and did not approach the equilibrium after 3 hour of osmotic dehydration. Solid gain at 60°C solution temperature for osmotically dehydrated carrot of 60% sugar and 3% salt concentration ranged from 2.34% to 5.86%. The findings of drying characteristics of osmo-convective tray drying showed that the drying time during tray drying for control and osmosed samples were 12 hrs and 8 hrs at 60°C. In osmo-convective dried carrot, average RBG value were 73.102 and 71.934 at 60'C and 70'C, respectively. Osmotically dried samples showed light color compared to fresh dried sample but color increased with the increase in temperature. The rehydration ratio of osmo-convective dried samples ranged from 2.8 to 2.94 while it was found to be 4.14 to 4.66 for hot air dried samples (control). Osmotically dried samples showed light color compared to fresh dried sample but color increased with the increase in temperature. Sensory evaluation reveals that the osmo-convective dried carrot was found best among all four samples with highest overall