Thermomechanical Properties of Durum Wheat Semolina Blends Enriched with Pumpkin Flesh and Peel Flour Evaluated by Mixolab

The incorporation of vegetable by-products into cereal products represents an effective strategy for improving nutritional quality while supporting sustainable food production. Pumpkin flesh and peel are recognised as valuable sources of dietary fibre and naturally occurring carotenoids and phenolic compounds, making them promising ingredients for cereal-based products. However, their influence on dough processing behaviour remains insufficiently understood. Therefore, this study evaluated the effects of pumpkin flesh flour (10, 25 and 50%) and pumpkin peel flour (10, 20 and 30%) on the thermomechanical properties of durum wheat semolina blends using the Mixolab system, which simultaneously measures dough behaviour during mixing and controlled heating and cooling, providing information on protein weakening, starch gelatinization, cooking stability, and starch retrogradation.

Progressive substitution with pumpkin flesh flour significantly increased water absorption from 57.3% in the control to 72.2% at 50% substitution, while dough development time increased from 3.27 to 7.75 min. Increasing flesh flour levels reduced starch gelatinization (C3), cooking stability (C4), and starch retrogradation (C5). At 50% substitution, C3 decreased from 1.864 to 1.271 Nm, C4 from 1.631 to 0.916 Nm, and C5 from 2.355 to 1.035 Nm.

Pumpkin peel flour produced an even greater increase in water absorption (63.2–77.0%) and prolonged dough development time (8.30–9.75 min). It also reduced C3 (1.589–1.472 Nm), C4 (1.131–0.845 Nm), and C5 (1.598–1.055 Nm), indicating reduced starch paste stability and lower retrogradation during cooling. In both formulations, C2 values remained relatively stable, suggesting that the observed changes resulted primarily from fibre–starch interactions rather than protein weakening.

These findings demonstrate that pumpkin flesh and peel flours substantially modify the thermomechanical behaviour of semolina doughs by increasing water absorption and reducing starch gelatinization and retrogradation. Pumpkin peel, as an underutilized processing by-product, shows particular potential as a sustainable functional ingredient for high-fibre cereal products.