Chlorophyll stability in spinach dehydrated by freeze-drying and controlled low-temperature vacuum dehydration
2001
An-Erl King, V. | Liu, C.F. | Liu, Y.J.
Freeze-drying and controlled low-temperature vacuum dehydration were used for the drying of both blanched and unblanched spinach. Monolayer moisture content and solid surface area of dehydrated products were determined by using moisture sorption isotherms and BET equation. Contents of chlorophylls a and b and TBA value were measured, and those variations in dried samples during storage were studied at different storage temperatures of 5, 20, 30, and 45 degrees C. Drying time of controlled low-temperature vacuum dehydration was much less than that of freeze-drying. Solid surface areas of products from freeze-drying were higher than those from controlled low-temperature vacuum dehydration, and blanching also exerted an effect on the increase of solid surface area of dried products. Chlorophyll contents decreased and TBA value increased with the increase of storage temperature and time. Those phenomena were more significant in the products of freeze-drying than those from controlled low-temperature vacuum dehydration, and more marked in blanched samples compared to unblanched.
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