Influência dos parâmetros de secagem e formas de fracionamento na composição química do gengibre (zingiber officinale roscoe) desidratado

Abstract

Ginger, rhizome of Zingiber Officinale Roscoe, is widely marketed for use in the food, chemical and pharmaceutical industries, especially in the dried and powder form. For this, it is necessary that the raw material undergoes a drying process, which can influence significantly its characteristics, so, during drying it is necessary to take into account the most desirable conditions of the product, from the standpoint of maintenance of their constituents. This work proposes to investigate the dehydration process of gingerd under three different fractionation forms: whole, sliced and grated; and submitted to three different drying processes: heater with forced air circulation (CC) and heater without forced air circulation and (SC), both at temperatures of 50, 60, 70 and 80°C, and freeze-drying. The obtained data allowed the construction of drying curves Xbs (t): moisture content of material (kg of product - kg dry mass) / (kg dry mass)) and curves of Aw (t): activity of water versus time of dehydration. The samples dehydrated by different processes were analyzed for color, phenolic compounds, thiobarbituric acid reactive substances (TBARS), acidity index, DPPH radical sequestration capacity, and chemical composition of the essential oils obtained by hydrodistillation. The results showed that the drying time ranged from 3.7 to 30.2 hours, and was dependent on the methodology used and the process temperature, in with the highest temperatures reaching lower humidity in a shorter time, as well, as the circulation and fractionation of the sample influenced the reduction of ginger dehydration time. Fractionation of the sample also reduced the drying time for all processes. For the color analysis, the different process temperatures did not provide significant changes, however, the more fragmented the sample, the lower the luminosity (L *), the tendency for red (H *) and increase in color intensity (C *). In the freeze-drying, the fractionation of the sample did not influence the color results. In the analysis of phenolic compounds, thiobarbituric acid reactive substances, acidity index and DPPH radical sequestration capacity, it was found that the lower temperature, the lower sample fractionation and the forced air circulation generated results closer for those of the in natura sample, that is, thus preserving the bioactive compounds. The results of the best method in heater were similar to those obtained by freeze-drying. The extraction yield of ginger oil by hydrodistillation ranged from 1.53 to 1.64%. It was observed that in all the drying processes analyzed there was a change in the composition of the oil when compared to the in natura sample, and the higher temperature and the larger sample fractionation the greater was the change. There was concentration and loss of some compounds as well as the formation of others.