Optimization of spray drying process for the microencapsulation of Ximenia americana bioactive compounds using pregelatinized sweet potato starch as a carrier agent

Ximenia americana L., commonly known as wild plum and locally referred to as “Tchaboule” in Fulfulde, is an underutilized medicinal fruit rich in antioxidant phytochemicals, particularly polyphenols and carotenoids. However, its high perishability considerably limits postharvest availability and utilization. This study aimed to optimize the spray drying microencapsulation of X. americana fruit juice using pregelatinized sweet potato starch as a carrier agent to maximize the retention of bioactive compounds while producing a stable powder. Response Surface Methodology (RSM) based on a central composite design was employed to evaluate the effects of drying temperature (140–170 °C), inlet air flow rate (60–80 m³/h), and carrier agent concentration (10–20 g/100 g juice) on drying yield, moisture content, and encapsulation efficiency of polyphenols and carotenoids. Increasing drying temperature, inlet air flow rate, and carrier agent concentration significantly improved powder yield while reducing moisture content. Multi-response optimization using a desirability function identified the optimal processing conditions as a drying temperature of 170 °C, an inlet air flow rate of 65.79 m³/h, and a carrier agent concentration of 20 g/100 g juice. Under these conditions, the predicted encapsulation efficiencies for polyphenols and carotenoids were 81.22% and 61.67%, respectively, with a final moisture content of 2.08% and a total phenolic content of 96.04 mg GAE/g powder. These findings broaden the range of alternative encapsulating materials available for spray drying and provide new opportunities for the valorization of underutilized tropical fruits and locally sourced starches in the development of functional food ingredients.