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Water Activity of Flour at High Moisture Contents as Measured with a Pressure Membrane Cell
Author(s) -
GURARIEH C.,
NELSON A. I.,
STEINBERG M. P.,
WEI L. S.
Publication year - 1965
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1965.tb00288.x
Subject(s) - moisture , water content , water activity , relative humidity , chemistry , humidity , membrane , porosity , wheat flour , materials science , food science , composite material , thermodynamics , biochemistry , physics , geotechnical engineering , engineering
SUMMARY A method was developed for the determination of water activities of flour at high moisture contents. In this method a flour sample was allowed to equilibrate with water contained in a porous membrane while under a certain constant mechanical pressure. The cell was fitted with a porous membrane which allowed the transfer. of moisture from and to the sample. After equilibrium was achieved the sample was analyzed for moisture content. A thermodynamic relationship enabled calculation of the water activity corresponding to the pressure used in the cell. Results obtained with this method were in agreement with those obtained with the constant‐relative‐humidity desiccator technique in the over‐lapping range of water activities. The two methods were also in agreement that the water activity of flour was not affected by the particle size distribution.