sublimation dehydration
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2022 ◽  
Vol 42 ◽  
pp. 02001
Author(s):  
Vladimir Alexandrovich Ermolaev ◽  
Dmitry Evgenievich Fedorov

The aim of the study was the selection of effective modes of rosehip sublimation dehydration. An Iney-6M unit was used for freeze drying. The selection of the duration of the sublimation stage and the final drying temperature was carried out. At the same time, such indicators as the duration of drying, organoleptic assessment and the preservation of vitamin C were analyzed. The duration of freeze drying of rose hips with a period of sublimation of 4, 5, 6 and 7 hours was 6, 7, 8 and 8.5 hours, respectively. It was found that with a decrease in the duration of the sublimation stage, a decrease in the quality characteristics of dry rose hips is observed. It was found that when the drying temperature changes from 70 to 40 °C, the drying time increases from 6.5 to 9.5 hours. At the same time, the loss of vitamin C also decreases. Based on the research, the most favorable modes of sublimation dehydration of rose hips have been determined - the final drying temperature is 50 °C and the duration of the sublimation stage is 5 hours. Under these modes, the duration of lyophilization is 8 hours, the total organoleptic assessment is 18.25 points out of 20, and the preservation of vitamin C is 27%. Lyophilized rose hips can be used as an independent product, or ground into powder for adding to other products - confectionery, dairy, bakery products, as well as biologically active additives and functional food.


1994 ◽  
Vol 116 (3) ◽  
pp. 686-693 ◽  
Author(s):  
E. P. Scott

A study of sublimation-dehydration within a porous medium as a result of volumetric heating, such as that associated with microwave heating, is presented in this paper. A semi-infinite frozen porous medium with constant thermal properties subject to a sublimation-dehydration process involving a volumetric heat source is considered. One-dimensional analytical solutions for dimensionless temperature, vapor concentration, and pressure were obtained. A sensitivity study was also conducted in which the effects of the material properties inherent in these solutions were analyzed. Finally, some of the assumptions used in the formulation of the problem were analyzed, and predicted drying curves were found to compare reasonably with previously published experimental results.


1974 ◽  
Vol 96 (3) ◽  
pp. 319-323 ◽  
Author(s):  
M. D. Burghardt ◽  
W. W. Bowley

The case of sublimation dehydration of a porous continuum is analyzed from the viewpoint of nonequilibrium thermodynamics. The general energy and mass transport equations are shown and the application of sublimation is illustrated.


1973 ◽  
Vol 95 (4) ◽  
pp. 516-520 ◽  
Author(s):  
L. L. Hardin ◽  
D. F. Dyer

A theoretical analysis as well as an experimental study of sublimation freeze-drying is reported. The theoretical and experimental results compare within 10 percent for a test case. In addition, the theoretical work confirms that drying rates increase linearly with bed thickness for particle bed drying, as reported in earlier experiments. Drying times for a slab and particle beds with the same mass and dryer surface area are compared. It is shown that the drying time for the particle bed can be reduced by more than a factor of two compared to the equivalent slab. It is also shown that the optimum way to increase the drying rate of particle beds is to increase the number of layers rather than the size of particles.


1970 ◽  
Vol 13 (5) ◽  
pp. 0559-0561 ◽  
Author(s):  
S. H. Cho and J. E. Sunderland

1968 ◽  
Vol 90 (4) ◽  
pp. 379-384 ◽  
Author(s):  
D. F. Dyer ◽  
J. E. Sunderland

An analytical study is presented for sublimation dehydration which shows the effect of the important mechanisms involved in the process. The effects of the presence of a binary gas mixture are considered. The boundary conditions for this solution are all directly controllable external conditions; namely, the temperature, total pressure, water-vapor partial pressure at the heated surface, and the temperature of the face opposite to the heated surface. The analysis involves the simultaneous solution of the appropriate equations of continuity, momentum, and energy, as well as the equation of state for each of the gas components present. Typical results are given for freeze-drying of bovine muscle. The drying rate is seen to increase with decreasing total pressure and water-vapor concentration. The relative importance of diffusional transport compared with bulk transport is presented. It is shown that drying rates can be substantially increased by judiciously making use of heat transfer through the frozen region.


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