Use of Lyophilization in Determination of Moisture Content of Dehydrated Vegetables

Abstract

A new reference method for the determination of moisture content of dehydrated vegetables involves addition of a large amount of water to a weighed sample of vegetable; freezing and drying in the frozen state (lyophilization); and completion of the drying in a vacuum oven or vacuum desiccator in the presence of an efficient water adsorbent. The last step can be completed in a relatively short time at, or slightly above, room temperature, because of a marked increase in drying rate brought about by lyophilization. Data presented for white and sweet potatoes, beets, and carrots show that the lyophilized materials can be dried unambiguously to constant weight and that the loss in weight may be taken as a measure of the moisture content.As the final dry weight is virtually independent, within wide limits, of the temperature of drying, the new method obviates the necessity of careful control of drying temperature.

Nutritional Composition ofOpuntia sulphureaG. Don Cladodes

“…Water content (moisture) was measured by sample dehydration by lyophilization, a method that has been used extensively for moisture determination in various vegetables (e.g. Makower and Nielsen 1948, Blanco et al 2008, Šircelj and Batic 2012. In fact, this freeze-drying method allowed us to obtain better quality products compared with products dried with traditional methods (Ciurzyńska and Lenart 2011).…”

Food

“…Vapor pressure measurements have been adapted to the study of the moisture content of dehydrated vegetables (121,236). A more recent method involves the use of lyophilization-i.e., freeze-drying in vacuum in the presence of a water absorbent (237). This method has the advantage of not requiring precise control of drying temperature, as the final dry weight is practically independent of the temperature.…”