ISSN:
1750-3841
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
The equilibrium isotherms and the rates of adsorption and desorption of water vapor by selected freeze-dried food materials were studied between −20 and 50°C with a spring-balance sorption apparatus. In simple freeze-dried gels (starch, gelatin) the quantity of adsorbed water at equilibrium increased as the temperature was lowered from 50 to 0°C, and it remained almost constant below 0°C. In freeze-dried foods (potato, peach, and raw beef) and sugar-containing starch gel, adsorption was maximum at between 10 and 30°C. The equilibrium vapor pressure of simple gels followed the Clausius-Clapeyron equation throughout the temperature range studied, and the same relationship applied to the foods at the high and low temperature regions, with a change of slope at about 20°C. The rates of adsorption and desorption at a pressure of 0.1 mm Hg remained constant at temperatures below 0°C, and they increased linearly as the temperature was increased from 0 to 50°C. As the pressure was raised from 0.1 mm Hg to atmospheric, the rates of adsorption at 30°C decreased by a factor of about 100. The adsorption rates at atmospheric pressure increased exponentially with the temperature between 0 and 50°C. The results are discussed in relation to the freeze-drying operation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2621.1965.tb01840.x
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