OPTIMIZATION OF SPRAY DRYING PARAMETERS FOR PRODUCING A WATER-SOLUBLE POWDER FROM BRAZILIAN NUT CAKE EXTRACT

The Brazilian nut (Bertholletia excelsa) is a fruit native to the Amazon rainforest in South America, known for its health-promoting components, including unsaturated oils and selenium. This study aimed to develop a water-soluble powder from the partially defatted Amazonian chestnut cake extract. The chestnut cake was milled and sieved (0.42 mm) to obtain flour. The extract was produced by mixing flour with water at a 3:1 ratio and agitating at 15,000 RPM for 10 minutes. Separation of the liquid extract from the residue was achieved by centrifugation at 8000 RPM for 5 minutes. The supernatant, a milky-looking extract, initially contained 9% total solids, which were increased to 16% using a rotary evaporator at 60 °C under 90 mbar vacuum. For standardization, the total solids were raised to 20% (w/w) by adding maltodextrin (10 DE) under agitation at 600 RPM, with i-carrageenan incorporated at 0.3% (w/w) of the suspension weight. The extract was homogenized using a disperser at 10,000 RPM. Spray drying was performed using a Box-Behnken experimental design with 12 trials and 3 central points, yielding 15 independent trials. The experimental variables included air inlet temperature (160, 175, and 190°C), feed flow rate of the concentrated extract (9,12, and 15 mL/min), and spray air flow rate (831, 1562, and 2293 L/h). The measured response variables were yield (%) and solubility (%); the desirability function was used to obtain the optimal response for both variables. Response surface methodology identified the optimal parameters: an air inlet temperature of 167 °C, a feed flow rate of 15 mL/min, and an air flow rate of 2293 L/h. This resulted in a yield of 46.82% ± 0.67 and a solubility of 77.19% ± 1.44 at 30 °C. Additional analyses included proximal analyses, particle-size distribution, SEM, and microbiological assessments. Results indicated that while higher temperatures increase yield, they decrease solubility, which is undesirable for a powder intended for reconstitution.