The Research Of Osmotic Pre-treatment Combined Microwave Dehydration Of Carrots

The combination of osmotic pre-treatment -mainly in sucrose solutions- and microwave dehydration of carrots has been studied.In the paper, researched some factors influencing of the efficacy dewatering of the osmotic dehydration by the orthogonal experiment of carrot. The factors were solution of sucrose, ratio of material to the solution, osmotic dehydration time, blanching or not, cross or vertical of cutting, thickness of carrot and cored or not. The results showed that blanching or not was the most significantly effect of rate of dewatering; no blanching of carrot removed water by immersion with sucrose solution was considered; the high solution of sucrose can preserve the color; ratio of material to the solution was effected by the initial solution of sucrose, the initial weight of carrot, rate of dewatering; the water removed was happened during 60mins of beginning; smaller was thickness, larger was dewatering rate; and the high efficiency design have been determined.Temperature and other factors were studied, the result showed temperature was not the most significantly effect of rate of dewatering.Carrots were used to study mass transfer during osmotic dehydration. Mass transfer was quantitatively investigated over a range of concentration (40-60°Brix) and temperature(30-57℃) of sucrose solution. Effective diffusion coefficients of water as well as sucrose were estimated using the solution of Pick's unsteady state law. Multilane analysis of the estimated effective diffusion coefficients of water and solute revealed that these values depend upon temperature and concentration of the osmotic solute as well as the combined effect of temperature and concentration.It was carried both osmotic pretreatment combined microwave drying and hot air drying of carrots. The results demonstrate that the microwave finish dried carrots was more high dewatering rate and rehydration value, and the color of rehydration's carrots was almost same the fresh carrots.The carrots with different moisture and solid content were dried by microwave. The mathematics model indicated that the results accord with the exponential model.