Distribution of Water between Wheat Flour Components: A Dynamic Water Vapour Adsorption Study

Abstract

The water adsorption properties of hard and soft wheat flours and flour components (starch, damaged starch, gluten, soluble pentosans, and insoluble pentosans) were determined at 25 °C using a controlled atmosphere microbalance. At different levels of relative humidity (from 10% to 95%), changes in sample mass (i.e., water gain) were continuously measured versus time and described using exponential models (R2≥0·994). Water adsorption isotherms were constructed for wheat flours and flour components and described using Guggenheim-Anderson-de Boer models (R2≥0·997). It was not possible to distinguish between the selected hard and soft wheat flours by their isotherms. The water-soluble pentosans had the highest water adsorption capacity. The theoretical distribution of water between the flour components (calculated using the Guggenheim-Anderson-de Boer parameters) was starch, 88%; gluten, 10%; and pentosans, 2%.