Influência das etapas de branqueamento e temperatura de secagem na composição bromatológica e na atividade antioxidante de folhas de erva-mate

Abstract

Yerba mate (Ilex paraguariensis) is a plant that after having its leaves bleached, dried and ground, is used in the manufacture of hot and cold drinks, traditionally consumed in southern Brazil and adjacent countries. Its popularity has grown in recent years, gaining recognition and increasing its consumption worldwide. One of the reasons for this is the relationship of the plant and health benefits, such as anti-tumor, antiinflammatory and antimicrobial effects. The bleaching and drying process are essential for the final product, causing chemical and physico-chemical impacts on the leaves. Unfortunately, due to the way that bleaching is carried out, it is common to have aggregation of pyroligneous compounds, such as PAHs, molecules widely associated with the development of cancer. Therefore, we sought to analyze the process chain of the leaves of yerba mate in order to seek a final product that is safer to health and with the highest amount of antioxidant compounds. For this, the behavior of the proximate composition and antioxidant activity in different processes of yerba mate was monitored through alternative bleaching, where the leaves were immersed in distilled water at 87 °C for 90 s. Dryings were carried out at 90, 100 and 110 °C, from mass measures performed during them, drying kinetics were obtained and used to determine a satisfactory descriptive mathematical model. Through statistical analysis, it was observed that, among the studied models, the Newton model was the one that best described the drying of yerba mate leaves, showing R2 between 0.9968 and 1.0000 and relative errors between 0.001 and 0.055. The proximate composition did not change significantly, either by traditional bleaching or by immersion in water. Thus, the mean values of 5.77 ± 0.74, 25.72 ± 2.41, 7.29 ± 1.64 and 6.90 ± 0.51% were obtained for ash, crude fiber, lipids and proteins, respectively. Analyzing the content of antioxidant activity by the methods using 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazin-1-yl (DPPH), ferric reducing ability of plasma ( FRAP) and total phenolic content (TF) were found to have an impact by the forms of bleaching and drying. The higher the drying temperature, the higher the levels of antioxidant activity were found. Taking the DPPH assay as an example, immersion bleached samples, that were dried after, presented antioxidant activity values from 283.50 ± 2.85 to 305.39 ± 5.98d μM ET g-1, while the in natura sample presented only 41.50 ± 2.60 μM ET g-1, however inferior to sapeco, with antioxidant activity between 336.61 ± 0.69 and 339.83 ± 2.91 μM ET g-1 Therefore, despite having lower values than traditional bleaching, immersion treatment can be a viable alternative during the yerba mate processing. Also, by means of a fuzzy inference system (FIS) and an adaptive neuro-fuzzy inference system (ANFIS), it was possible to determine the amount of TF from experimental data of ABTS, DPPH and FRAP; showing absolute error mean, percentage error mean, and square error mean of 1.555, 0.105, and 8.239, respectively.