Valorisation of Partially Defatted Pistachio Flour as a Value-Added Ingredient for Gluten-Free Cookie Production

Valorisation of oil-extraction by-products as food ingredients can improve resource efficiency while enhancing the nutritional quality of gluten-free products. This study evaluated partially defatted pistachio flour (PDPF) as a substitute for rice flour (10–40%) in gluten-free cookies. Dough rheology was characterised by oscillatory and creep–recovery tests, while cookie proximate composition, physical properties and sensory acceptance were determined. PDPF incorporation progressively increased maximum creep compliance from 21 to 36 MPa−1 and decreased steady-state viscosity, indicating greater deformability. In the cookies, protein increased from 4.1 to 14.3 g/100 g and fibre from 0.8 to 3.7 g/100 g, while fat remained essentially constant through formulation adjustment. PDPF reduced spread factor and markedly increased breaking force, which rose from 5.0 to 23.8 N, and produced progressively darker and redder cookies. Despite these instrumental changes, consumer texture-liking remained comparable to the control up to 30% PDPF. Cookies containing 10–30% PDPF showed higher appearance, taste and overall acceptance than the rice-flour control, whereas the 40% formulation lost this sensory advantage. A 30% PDPF substitution provided the most favourable balance between nutritional enrichment, technological performance and consumer acceptance, supporting the use of PDPF as a high-value ingredient for gluten-free cookie production and contributing to pistachio by-product valorisation.