Optimisation and physicochemical characterization of nano spray-dried phenolic extracts from aloysia citriodora using maltodextrin–CMC matrices

The susceptibility of phenolic compounds from Aloysia citriodora to degradation limits their practical applications. This study optimised their microencapsulation by nano spray drying using response surface methodology (Box–Behnken design). By evaluating maltodextrin, carboxymethyl cellulose (CMC), and guar gum as wall materials, their effects on encapsulation yield, encapsulation efficiency, flavonoid content, and hydroxyl radical scavenging activity were investigated. Multi-response optimisation identified an optimal matrix consisting of 58.42% maltodextrin and 41.57% CMC. Experimental validation confirmed the model predictions, achieving an encapsulation yield of 71.49% and remarkable antioxidant activity against hydroxyl radicals (IC50 = 2.08 mg/mL). HPLC–MS analysis verified the successful preservation of key metabolites such as verbascoside and martynoside, while scanning electron microscopy revealed spherical particles with an average size of 2.27 μm. In conclusion, the maltodextrin–CMC matrix represents an effective strategy for protecting the antioxidants present in Aloysia citriodora, supporting its potential application in food and nutraceutical products.