Secagem do extrato aquoso de gengibre (Zingiber officinale Roscoe) pelo método de camada de espuma

Abstract

Belonging to Zingiberacea family, ginger (Zingiber officinale Roscoe) has rhizomes with the aspect of misshapen hands, rich in water and widely used in food industry as raw material. The drying process of solids comes as an alternative for food conservation because it reduces the water level, increasing the final product stability, aiding to the development of new products and reduction of mass and volume, considerably decreasing the transportation and handling costs. The foam layer method provides the use of low temperatures and shorter dehydration time because the higher surface exposed to the air, creating products with a better nutritional quality, with a short operational time, when compared to other drying processes. The objective of this study was to use the foam mat method for drying an aqueous ginger extract (EAG) and characterize the product obtained. Eleven experiments were performed with four factors varying in three levels: temperature (60, 70 and 80 °C), relationship ginger/water (0.3, 0.4 and 0.5 g/mL), stirring time (7, 14 and 21 min), and the thickness of the foam layer (0.5, 1.0 and 1.5 cm). The combination of factors was obtained by the Statistica 7.0 software. It was studied and evaluated the drying kinetics, through mathematical models of Newton, Henderson-Pabis and Page. It was determined the physical and chemical characteristics of the powder obtained: absolute density; apparent density antioxidant activity; color parameters (L *, a * and b *); porosity; solubility and moisture. The model with the best adjustment to the experimental data was the Page model, as showed higher R2 values (between 97.29 to 99.57) and lower average relative errors (between 1.47 to 7.42%); Related to the absolute density, the highest response was obtained at 80 ° C, 0.5 g/mL of ginger/water relationship, 21 minutes of stirring and the foam thickness of 0.5 cm. For the apparent density, higher values were obtained with 0.4 g/mL ginger/water relationship, 14 min of stirring, 1 cm of foam thickness and temperature of 70 °C. For the antioxidant activity, the obtained powder ranged from 65.13% to 79.25%. Color parameters (L *, a * and b *) were not significantly affected by the treatments. With respect to porosity, higher values were obtained with conditions of 60 °C temperature, 0.5 g/mL of ginger/water relationship, 7 min of stirring and 1.5 cm of layer thickness. Regarding the solubility and humidity, both variables showed higher values (10.12% and 6.66% respectively) when dried at 60 °C with 21 min of stirring, 0.5 cm of layer thickness and 0.5 g/mL of ginger/water relationship. Generally, each treatment resulted prominent features, thus the best treatment depends on the area in which to apply the product.