Avaliação termoanalítica e cromatográfica de amidos incorporados com extratos crioconcentrados de erva-mate

Abstract

Yerba mate (Ilex paraguariensis) has a high content of phenolic compounds (phenolic acids and flavonoids), methylxanthines (theobromine and caffeine) and saponins. Starch is an excellent excipient, able to binding other molecules in its structure and transporting in the body. Starches incorporated with yerba mate extracts can bring health benefits, how to decrease lipids and glycemic indexes, decrease oxidative stress and stimulate the Central Nervous System (CNS) and the body fat burning. The freeze concentration technique is very relevant to obtain yerba mate aqueous extract with a higher content of bioactive compounds without changes in the chemical properties. The aim of this work was to evaluate the incorporation of the freeze concentrated yerba mate extracts in corn starch, using thermoanalytical and chromatographic methods. The steps of freeze concentration were evaluated by increasing of the density (D), of the total solids contents (ST), ash and organic matter (MO). In the ST analysis, ash (C) and MO the concentration factor ranged from 116.14% to 336.01% comparing all stages of the freeze crioconcentration process, however the highest values were found between EI and C2 steps. The efficiency between the crioconcentration steps ranged between 32.23% and 66.01% for ST, 34.79% to 73.24% for MO and 15.59% to 49.31% for ashes. The concentrations of some bioactive compounds in the yerba mate extracts were also evaluated (5-caffeoylquinic acid, 3,5-dicafeoquímico acid, rutin, theobromine and caffeine) by High Performance Liquid Chromatography (HPLC). In these results it was observed that 5-caffeoylquinic acid, 3,5-dicafeoquímico acid, rutin, theobromine and caffeine (bioactive compounds present in yerba mate), increased significantly between EI and C2 steps. Through thermal analysis was evaluated the interaction of corn starch with the bioactive compounds of the yerba mate aqueous extracts. The curves obtained through the analysis of Thermogravimetry and Differential Thermal Analysis (TGDTA) curves showed that the intensity of exothermic peaks increased with freezeconcentration steps advance. These results confirm that there was an increase in oxygen levels, releasing energy at higher temperatures. In the Differential Scanning Calorimetry (DSC) analyzes it was observed that the incorporated corn starch samples with yerba mate extracts had the values of gelatinization enthalpy (ΔH) increased in all stages of freeze concentration. These results showed that the oxygenated compounds of yerba mate (polyphenols and methylxanthines) were incorporated into the starches, as they changed their thermal properties. The use of the yerba mate extracts incorporating technique into the starches together with the freeze concentration process can be useful for the development of a nutraceutical food, searching products with functional qualities.