Green Extraction Coupled With Spray-Drying Encapsulation Enhances Stability and In Vitro Bioaccessibility of Phoenix dactylifera Seed Bioactives

The valorization of date seed by-products as sources of bioactive compounds represents a promising strategy for supporting sustainable and circular food systems. This study evaluated ultrasound-assisted extraction (UAE), high-pressure autoclave extraction (HPAE), and sequential UAE followed by HPAE for the recovery of bioactive compounds from Tunisian date seeds. The most effective extraction condition was subsequently subjected to spray drying using an alginate-xanthan gum wall matrix. Encapsulated (EP) and non-encapsulated (NEP) powders were evaluated for physicochemical properties, phenolic composition, antioxidant activity, storage stability, and in vitro gastrointestinal bioaccessibility using the INFOGEST 2.0 protocol. Among the extraction conditions investigated, HPAE for 30 min (HPAE30) produced the highest total phenolic content (TPC), reaching 133.71 ± 1.14 mg GAE/g dry matter, compared with 31.68 ± 0.16 mg GAE/g for UAE30 and 63.78 ± 0.83 mg GAE/g for sequential UAE15-HPAE30. HPAE30 also showed the highest DPPH antioxidant activity (82.52 ± 0.01 μM TE/g dry matter), whereas the sequential treatment showed lower DPPH activity (32.70 ± 0.02 μM TE/g). HPAE30 was therefore selected for subsequent spray drying. The resulting powder showed an encapsulation efficiency of 34.26%, while EP exhibited lower water activity (0.35 ± 0.002) than NEP (0.65 ± 0.001). During 14 days of storage under light exposure, TPC decreased from 39.01 ± 0.33 to 30.15 ± 0.50 mg GAE/g in NEP, whereas EP retained approximately 95% of its initial TPC. Following in vitro gastrointestinal digestion, the TPC-based intestinal bioaccessibility index was 66% for EP compared with 58% for NEP. Overall, HPAE30 provided the highest recovery of phenolic compounds under the conditions investigated, while alginate-xanthan encapsulation improved the retention of phenolic compounds during storage and was associated with higher in vitro intestinal bioaccessibility compared with the non-encapsulated powder.