Efecto del secado por túnel, liofilización y atomización sobre la capacidad antioxidante y compuestos fenólicos de huacatay

The aim of the study was to evaluate the effect of three kinds of drying: tunnel drying (at 50, 60 and 70 °C), freeze-drying (secondary drying at 40, 55 and 70 °C) and spray-drying (at 150, 160 and 170 °C) on the antioxidant capacity and phenolic compounds on huacatay (Tagetes minuta) leaves. Besides, for spray-drying, leave extracts were prepared (5 % soluble solids), and then, dried by a spray system by using two encapsulants: maltodextrin (10 dextrose equivalents, DE) and modified starch, at concentrations of 0.0, 0.5 and 1.5%. The antioxidant activity and phenolic content were measured by DPPH and Folin-Ciocalteu methods. In the samples subjected to tunnel drying (50, 60 and 70 °C) retention rates of antioxidant capacity of 40.00, 40.75 and 28.67%, and phenolic content of 64.30, 61.80 and 57.34%, respectively, were obtained. While for the freeze-dried samples (40, 55 and 70 °C) retention rates of antioxidant capacity of 58.20, 64.89 and 53.32%, and phenolic content of 80.12, 92.04 and 83.08%, respectively, were obtained. In the case of the spray-drying, no significant differences were obtained for the antioxidant activity respect to type of encapsulant, however, an significant effect respect to the temperature was observed, with retention rates from 44.6-45.7% (150 °C), 39.5-40.7% (160 °C) and 38.4-39.5% (170 °C). Besides, the antioxidant activity decreased as the concentration of the encapsulant. Finally, samples with the best results (tunnel drying 60 °C, freeze-drying 55 °C and spray-drying 150 °C), were subjected to a 90-days evaluation period, and the best preservation of the antioxidant activity was observed in the freeze-dried samples.