Fiber and polyphenol enriched biscuits using date palm byproduct: Physiochemical characteristics, sensory properties, in vitro digestion, and storage stability.

Functional biscuit was formulated by fortifying them with polyphenolic extract and fiber-rich residue of defatted date seed powder (DDSP) obtained through microwave-assisted extraction. Effect of particle size (small, medium, and large) and substitution level (2.5%, 5%, and 7.5%) of fiber-rich residue, along with the phenolic extract, on bioactive, physical, textural, and gastrointestinal digestion of fortified biscuits was studied followed by sensory and shelf-life studies. The total phenolic content (TPC) and antioxidant properties of biscuits increased with increasing substitution levels and particle size. DDSP residue fortification increased the fiber content in biscuits. Large particles of the residue-fortified biscuits showed significantly higher (p < 0.05) hardness compared to the control biscuits. Diameter of the biscuits decreased with increasing substitution level and particle size of fiber-rich residue with the lowest value of 50.66 mm in 7.5% substitution of large particles. The 7.5% substitution level of small particles resulted in the lowest spread ratio of 8.97 and the highest thickness of 5.79 mm. Consumer perceptions were at an acceptable level after the fortification, with an average sensory score of 6.02 out of 9 for overall acceptability. After 24 weeks storage, TPC decreased in biscuits, but TPC retention increased with increasing substitution level and particle size of residue. Thiobarbituric acid reactive substances (TBARS) value of biscuits increased with storage. The highest phenolic recovery was observed in the intestinal phase of the gastrointestinal digestion with the highest recovery of 102.33 at 2.5% level of large particles. Thus, phenolic extract and fiber-rich residue incorporation was effective to enhance the nutritional and functional properties of biscuits. PRACTICAL APPLICATION: Date seeds are rich in bioactive components and fiber. This study demonstrated the feasibility of utilizing date seeds to improve nutritional and functional properties of bakery products. The incorporation of the microwave-assisted polyphenolic extract and the fiber-rich residue of defatted date seed powder into biscuit enhanced the bioactive, nutritional, and functional characteristics while maintaining the consumer acceptance. This research contributes to the valorization of byproducts in the agriculture and food industries, promoting sustainability and a bio-circular economy.