Optimization of Spray Drying Process for Syringa Leaf Extract via Plackett-Burman Combined With Box-Behnken Method

Objective Syringa leaf extract (SLE) is a promising green feed additive with antibacterial and anti-inflammatory activities, mainly attributed to its main bioactive component tyrosol. However, its large-scale application is limited by the lack of an optimized spray drying process that ensures both process efficiency and tyrosol stability. Methods This study optimized the spray drying process of SLE with powder yield and moisture content as core indicators, using maltodextrin as a carrier material. Plackett-Burman (PB) design screened inlet air temperature, atomization frequency and feeding speed as key factors from six parameters. Box-Behnken design (BBD) combined with response surface methodology was then used for further optimization, and thermogravimetric analysis verified the thermal stability of tyrosol, the main bioactive component of SLE. The optimized process was validated by determining the angle of repose, solubility, dispersibility, and tyrosol content. Results The optimal parameters were determined as inlet air temperature 163°C, atomization frequency 349Hz and feeding speed 17 r·min -1 , under which three verification batches yielded an average powder yield of 82.8% and moisture content of 2.19%, consistent with model predictions. Tyrosol was stable below 225.1°C, matching the spray drying temperature range. Physical property tests confirmed excellent flowability, solubility and dispersibility of the optimized SLE powder, and tyrosol content determination in nine batches showed a coefficient of variation of 4.38%, indicating good process stability. Conclusion The spray drying process optimized by the PB combined with Box-Behnken method is stable, feasible, and reproducible, which can provide a scientific reference for the large-scale preparation production of SLE.