From by-product to wellness: nanoencapsulation of date peel extract in caseinate for functional yogurt

This study investigates the valorization of date peel, a by-product of date processing, by extracting its bioactive compounds and nanoencapsulating them with sodium caseinate for use in functional Yogurt. Date peel extract (DPE) from the Sukkari cultivar was obtained via ethanol extraction and characterized by high-performance liquid chromatography, which revealed a rich profile of phenolic compounds, including quercetin and gallic acid. The DPE exhibited high levels of total phenolic and flavonoid content, as well as notable antioxidant activity. Nanoencapsulation was achieved using high-speed homogenization and ultrasonication (15,000 rpm for 5 min, then 15 min of ultrasonication at 160 W) at extract-to-caseinate ratios of 50, 100 and 150 mg/g, producing sodium caseinate nanoparticles with z-average diameters of 95.78 to 118.20 nm (PDI 0.356 – 0.650, i.e., a moderate to broad size distribution) and encapsulation efficiencies up to 92.15%. These nanoparticles were incorporated into Yogurt, and the resulting products were evaluated for physicochemical properties, microstructure, texture, and sensory attributes over 30 days of refrigerated storage. Compared with the control, yogurts fortified with nanoencapsulated DPE showed higher DPPH radical scavenging activity, total phenolic and flavonoid contents, and hardness (p < 0.05), and at equal DPE doses their antioxidant values were also higher than those of yogurts with free DPE; sensory scores were not lower than those of the control. Blank caseinate nanoparticles accounted for 40–54% of the TPC, TFC and DPPH values of the loaded nanoparticles, and no caseinate-only yogurt control was included, so part of the protein, texture and antioxidant effects may be due to the caseinate carrier itself. These results suggest that date peel, a by-product of date processing, can serve as a source of phenolic compounds for yogurt fortification; however, no environmental or economic assessment was conducted.