VALORIZATION OF PURPLE CORN HUSK (Zea mays L.) AS A SOURCE OF BIOACTIVE COMPOUNDS THROUGH MICROENCAPSULATION

Purple corn (Zea mays L.), a native Andean variety from Peru, stands out for its high phenolic content, especially anthocyanins, the pigments responsible for its characteristic color and recognized bioactive potential¹. Although kernels and cobs are more explored, the husk remains an undervalued agro-industrial by-product. However, anthocyanin instability under light, temperature, and pH limits their technological application, making microencapsulation a promising strategy². Spray drying, a scalable technique, enables the incorporation of these compounds into foods, using maltodextrin as a low-cost, food-grade wall material³. This study evaluated purple corn husk as a source of bioactive compounds and developed spray-dried microcapsules for future food applications. The husk was ground and subjected to two maceration cycles with a solution of deionized water, ethanol, and acetic acid (60:39:1, v/v/v) at a 1:40 g/mL ratio. The extracts were centrifuged, filtered, and concentrated under vacuum. For microencapsulation, the extract was homogenized with 10% maltodextrin and spray-dried (inlet temperature: 110 °C; outlet temperature: 60 °C). Total phenolic compounds (TPC) and total monomeric anthocyanins (TAC) were determined by spectrophotometry, as was antioxidant capacity by the DPPH and ABTS methods; antioxidant capacity by the ORAC method was determined by fluorometry. Additionally, the extract (0.02 g/mL) was evaluated for in vivo acute toxicity in Galleria mellonella larvae model, while the microcapsules were evaluated for encapsulation efficiency. Results are expressed as mean ± standard deviation (n = 3). The husk extract showed high contents of TPC (33.10 ± 1.23 mg GAE/g, DW) and TAC (22.02 ± 0.71 mg C3G/g, DW), confirming its bioactive potential. No acute toxicity was observed in G. mellonella, with 100% larval survival at the tested concentration, providing preliminary evidence of safety. The microcapsules showed high encapsulation efficiency (95.33 ± 0.03%), indicating good retention of the extract within the matrix. TPC and TAC values per gram of microcapsule decreased, possibly due to dilution by maltodextrin and structural changes in anthocyanins during spray drying. Antioxidant activity was maintained relative to the extract, although distinct responses were observed among the DPPH, ABTS, and ORAC assays, reflecting their different reaction mechanisms. However, stability under light, temperature, and pH remains to be evaluated. In conclusion, purple corn husk is a promising source of bioactive compounds with no acute toxicity observed in the preliminary safety assessment, and its microencapsulation by spray drying preserves the antioxidant potential of the extract. Thus, this agro-industrial by-product has potential for the development of functional ingredients and natural colorants, although stability and food matrix application studies are still required.

Acknowledgments: This study was financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001; ESALQ/USP