Valorizing date seeds in biscuits: A novel approach to incorporate bioactive components extracted from date seeds using microwave-assisted extraction

Date seeds contain various nutrients and bioactive compounds which can be utilized as functional food ingredients in a sustainable manner. This study optimized microwave-assisted extraction (MAE) of bioactive compounds from defatted date seed powder (DSP) and investigated the physicochemical properties of the remaining residues from seeds of three different date varieties (Khalas, Fardh, and Khenaizi). Both, the extracts and the residues were incorporated as functional ingredients in the biscuits. Under optimal conditions: power 700 W, time 6 min, temperature 45 °C, and particle size $<125\mu m$, the total phenolic content (TPC) and total flavonoid content (TFC) were 15.88 mg GAE/g DSP and 8.51 mg QE/g DSP, respectively, while the antioxidant activities were 17.93, 61.68 and 39.74 mmol TE/g DSP for 2,2${}^{{}^{\prime }}$ -azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrlthydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP), respectively. Bioactive properties were significantly different (P<0.05) among three DSP varieties. The main phenolic compounds identified in defatted DSP were benzoic acid, catechin, ferulic acid, caffeic acid, and vanillin. Moisture content, water holding capacity (WHC), and color of the defatted DSP were significantly affected by microwaves. DSP extract and residue fortified biscuits showed enhanced TPC, TFC, and antioxidant properties. This study indicates that date seeds can be successfully used in food products to promote more sustainable food production.