Functional cookies formulated with pistachio green hull extract; physicochemical, antioxidant, antidiabetic, sensory, and in vitro digestion properties

Pistachio green hull extract (PGHE), a polyphenol-rich by-product of pistachio processing, serves as a potent natural source of antioxidants and enzyme-inhibiting compounds. This research aimed to formulate sugar-free functional cookies fortified with 2, 4, and 6 g/100 g PGHE and to assess their dough rheological characteristics, physicochemical, antioxidant and antidiabetic activities, in vitro digestion behavior, and sensory qualities. Frequency sweep analysis revealed that all doughs exhibited weak gel-like behavior (G′ > G″). PGHE incorporation reduced both storage (G′) and loss (G″) moduli, with the greatest decrease observed at 2 g/100 g, while higher PGHE levels (4 and 6 g/100 g) partially restored dough viscoelasticity, indicating concentration-dependent protein-polyphenol interactions. PGHE addition significantly enhanced total phenolic content (from 4.47 to 16.70 mg GAE/g dw) and antioxidant activity (up to 6.10 mmol Trolox eq/g dw) of cookies. A strong dose-dependent inhibitory action on α-amylase and α-glucosidase activities was found, indicating PGHE’s potential to modulate carbohydrate digestion and glycemic response. In vitro digestion confirmed a reduction of up to 17.5% in final reducing sugar release and sustained antioxidant activity in fortified cookies. Textural analysis showed that PGHE incorporation reduced hardness, gumminess, and chewiness, resulting in softer cookies. Sensory evaluation revealed good overall acceptability up to 4 g/100 g PGHE, while higher concentrations reduced aroma and taste perception. These findings demonstrate that PGHE is an effective functional ingredient for producing sugar-free cookies with improved bioactive properties, and potential health benefits for glycemic control.