Influence of Processing Operations on the Functional and Rheological Properties of Legume Flours

The growing demand for sustainable alternative protein sources has increased interest in legume flours as functional ingredients for innovative food applications. Their technological performance depends not only on botanical origin and composition, but also on processing conditions, such as soaking, cooking, milling, drying, and particle size reduction. This study evaluated the functional and rheological behaviour of chickpea, grass pea, and lupin flours subjected to different processing conditions, aiming to identify their potential applications in food matrices.

Grass pea, chickpea, and lupin flour samples were obtained using different processing operations, including direct milling, soaking, cooking, drying, and sieving. Functional properties were assessed through moisture content, water, oil, and milk absorption capacity, swelling power, foaming and emulsifying properties, and gelation capacity. For rheological analysis, all flours were sieved to 250 µm to minimize particle size effects. Gel systems at 6% (w/v) were prepared and analysed using rotational rheometry at 20 ± 1 °C. Stress sweep tests were performed to define the linear viscoelastic region, followed by frequency sweep tests. Storage modulus (G′) and loss modulus (G″) were evaluated at 1 Hz. Data were analysed by ANOVA followed by Tukey’s test at p < 0.05.

Lupin flour showed significantly higher water and milk absorption capacity, swelling power, and moisture content, indicating high hydration potential. Grass pea flour exhibited the highest foaming capacity, above 90%, suggesting suitability for aerated products. Soaking improved chickpea emulsifying properties by approximately 25% compared with the untreated sample. Rheological results showed that directly milled chickpea presented higher structural rigidity, whereas commercial chickpea flour showed lower G′ values and greater susceptibility to deformation.

Legume flours presented distinct functional and rheological profiles strongly influenced by processing conditions and particle size. These results support their targeted use in bakery, emulsion-based, aerated, dough-based, and fluid food products.