Publication no. C-2002-0603-01R |  VIEW ARTICLE

Frozen and Unfrozen Water Contents of Wheat Flours and Their Components.

Alma Delia Roman-Gutierrez (1), Stéphane Guilbert (1), and Bernard Cuq (1,2). (1) Laboratoire Technologie des Céréales et des Agro-Polymères, ENSAM—INRA Montpellier, 2 place Pierre Viala, 34060 Montpellier, Cedex 1, France. (2) Corresponding author. E-mail: <cuq@ensam.inra.fr> Cereal Chem. 79(4):471-475. Accepted January 23, 2002. Copyright 2002 American Association of Cereal Chemists, Inc.

The properties of frozen and unfrozen water in two different wheat flours (hard and soft), and in their main components (gluten, starch, damaged starch, water-soluble and water-insoluble pentosans), were described using modulated differential scanning calorimetry (DSC). As a reference, enthalpy values of crystallization (298 J/g) and melting (335 J/g) of pure water were determined from the total heat flow curves. The separation of thermal events between the reversing and nonreversing heat flows with modulated DSC was not effective due to disturbances in the modulated temperature scan. For wheat flours and their components, linear regressions described well the changes in frozen water content calculated from enthalpies of freezing (R(^2) = 0.970-0.982) or melting (R(^2) = 0.783-0.996). The unfrozen water content (UFWC) calculated for the hard wheat flour (29-31%, db) was close to that calculated for the soft wheat flour (30-32%). The UFWC of wheat gluten (38-47%), starch (38-42%), damaged starch (37-40%), water-soluble pentosans (51%), and water-insoluble pentosans (40-44%) were higher than the corresponding values for the flours. The simple summation of the contributions of each component cannot be used to estimate the overall behavior of flours.