Development and Characterization of Saffron Nanoemulsion Incorporated into Coffee Beverage Using Ultrasonic Emulsification and Ionic Gelation

Development and Characterization of Saffron Nanoemulsion

Abstract

This study presents the development of a novel functional coffee beverage enriched with saffron (Crocus sativus L.) bioactives, employing an integrated strategy of ultrasound-assisted extraction, ultrasonic emulsification, and chitosan–alginate ionic gelation to address the inherent instability of saffron phytochemicals. Spray-dried saffron nanoemulsions (0.1–4% w/v) were successfully formulated and encapsulated via ionotropic gelation, then incorporated into a black coffee matrix. The resulting systems were comprehensively characterized in terms of physicochemical properties, particle size distribution, chromatographic composition, antioxidant activity, and sensory performance during storage.

Sensory optimization identified formulation SC05-2 (4% w/v saffron nanoemulsion) as the most acceptable, achieving the highest scores for aroma (4.30 ± 0.95), taste (4.30 ± 0.67), and color (4.60 ± 0.84). High-performance liquid chromatography confirmed effective preservation of key non-volatile bioactives, with picrocrocin and total crocin contents of 336.58 mg/L and 241.15 mg/L, respectively, while the volatile safranal was reduced to 0.11 mg/L, likely due to processing losses. Dynamic light scattering analysis revealed successful nanoencapsulation, with a mean hydrodynamic diameter of 179.6 nm and a dominant subpopulation at 96.89 nm (99.8% number distribution). However, a polydispersity index of 0.462 and a zeta potential of −7.87 mV indicated moderate heterogeneity and limited electrostatic stability.

The saffron-enriched coffee demonstrated enhanced antioxidant activity (22.5%) compared to the control (21.8%), suggesting that the biopolymer-based encapsulation enabled controlled release of bioactives and mitigated oxidative degradation. Colorimetric analysis over 35 days (CIELAB) revealed a significant decrease in lightness (L* 55.92 to 41.29) alongside an increase in redness (a* 26.85 to 28.75), confirming sustained diffusion of crocin pigments into the beverage matrix. Statistical analyses (Friedman and Kruskal–Wallis tests) indicated significant temporal changes (p < 0.05) in both sensory and physicochemical attributes.

Overall, the findings demonstrate that the combined use of ultrasonic emulsification and chitosan–alginate ionic gelation is a promising approach for the development of premium functional coffee beverages. Despite the need for further optimization of colloidal stability, this system effectively enhances bioactive retention, sensory quality, and functional performance.