Characterization and antioxidant activity of turmeric extract (Curcuma longa L.) encapsulated using carbohydrate-based delivery systems by freeze-drying technique

Turmeric ( Curcuma longa L.) has grown in popularity among consumers in recent years due to its biological and antioxidant properties. However, the poor aqueous solubility and high sensitivity to environmental factors limit its beneficial uses. This study aimed to encapsulate turmeric extract into a maltodextrin and arabic gum matrix (60:40) by freeze-drying technique to determine the physico-chemical characteristics, particularly antioxidant properties of encapsulated turmeric extract in comparison to turmeric powder (TP) and turmeric extract (TE) in three different proportions (5, 10, 20 mg/mL). Physicochemical properties, including particle size distribution, morphology structure (X-ray diffraction, FTIR spectrum, SEM), encapsulation yield (EY %), water solubility, heat stability, and antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) were assessed. The results showed that the encapsulation approach was beneficial for the formation of turmeric microcapsules (TM) in the range of 190-257 nm, exhibiting uniform distribution of particles, high solubility in water (95.34-96.9%), improved heat stability, and high EY (94%). The fourier-transform infrared (FTIR) spectrum of TM indicated that the chemical structure of curcumin was mostly maintained, demonstrating effective encapsulation. The turmeric extract showed the highest antioxidant activity (2.83 - 3.19 μM Fe 2+ /g) and antioxidant capacity against DPPH (102.85-143.3%). However, TM displayed high resistance with a slower reduction in antioxidant activity under thermal processing over the temperature range 20–100 °C. The study concluded that encapsulation of TE is a beneficial technique that considerably elevates the thermal stability and antioxidant activity, thereby enhancing its prospective role as a functional constituent in the food sector.