Changes in the rheological, textural, microstructural and in vitro antioxidant properties of biscuit dough by incorporation of the extract and fiber-rich residue obtained through green extraction of defatted date seeds

The present study aimed at utilization of aqueous extract and fiber-rich extraction residue of defatted date seed powder (DDSP) as functional ingredient for improving the quality attributes of biscuit dough. Previously optimized microwave-assisted extraction (MAE) was used to recover the bioactive compounds from small, medium and large sized DDSP particles. Extracts and 2.5 %, 5 % and 7.5 % substitution levels of fiber-rich residue were incorporated in dough formulations, before rheological, physical and bioactive properties of dough were investigated. Smallest particles at 7.5 % substitution level resulted in the highest storage (G′) and loss moduli (G″) and lowest creep strain showing the highest resistance to deformation in the dough. Hardness increased with decreasing particle size and increasing substitution level of extraction residue. Highest substitution level with smallest particle size resulted in the darkest dough. Highest total phenolic content (TPC) of 0.60 mg GAE/g was found in the dough with 7.5 % substitution level by medium sized particles. The highest DPPH radical scavenging activity and Ferric reducing antioxidant power (FRAP) values were 2.00 mmol TE/g and 0.34 mmol TE/g, respectively, for small sized particles and 7.5 % substitution level of extraction residue. Substitution of DDSP fiber-rich extraction residue altered the structural arrangement of gluten in the dough. • Fiber-rich extraction residue significantly affected the viscoelastic properties of dough. • Dynamic moduli increased with decreasing particle size of the extraction residue. • Protein secondary structure was affected by the incorporation of extraction residue. • Addition of the fiber-rich fraction of DDSP increased the bioactivity of the dough.