Cinética de secagem da beterraba (beta vulgaris l.) obtida por refractance windows e caracterização fisico-quimica.

Abstract

The use of natural dyes is growing due to consumers' adoption of healthy and balanced diets. Beetroot (Beta vulgaris L.) is a root vegetable with water-soluble betalain pigments, divided into betacyanins, which have a red-violet coloration, and betaxanthins, which have a yelloworange coloration. Since they have bioactive compounds that are sensitive to oxygen, light, heat, and water, microencapsulation through drying is suitable. The choice of dehydration method is also important for the final quality of the product. The objective of this work was to study the drying kinetics of beetroot extract using different carriers by refractance window (RW), the temperature profile, yield, and the physicochemical characterizations of the raw pulp, pulp with carrier agents, and the powder obtained. After extracting the beet juice, 14% (w/w) of bagasse was added for subsequent addition of carrier agents: modified starch and maltodextrin DE 20. During drying, kinetic analysis and infrared thermography reading were performed. The pH and °Brix analyses were performed for the raw beet, added with carrier agent and the rehydrated powder; for the dry powder obtained, the process yield, moisture content, water activity, particle size, ash, colorimetry, solubility, wettability and X-Ray fluorescence spectroscopy (FRX) were analyzed. The results showed that drying beet with carrier agent was viable, the kinetics presented diffusion coefficients ranging from 1,17 x 10-3 to 1,87 x 10-3 cm2 /min. The thermography analysis showed that the samples followed the same temperature behavior profile during the dehydration process. The beetroot powders showed low moisture values, ranging from 6,05 to 9,12%, and water activity between 0,31 and 0,34. The solubility showed excellent reconstitution values of the samples. Furthermore, the °Brix analysis of the rehydrated powder was close to that of the in natura beetroot, and the pH results are within the stability range of betalain. The granulometry using maltodextrin presented a finer morphology than the modified starch. The wettability exhibited shorter times for the samples with maltodextrin, in addition, it was higher for higher concentrations of carrier agent. The colorimetry showed that the red color was present in the samples, without high denaturation. The percentages of minerals most found using the two types of carrier agents were potassium oxide (K2O) and chlorine (Cl). The best powder for storage was the one with 30% modified starch, due to its low results of water activity and moisture. It is therefore concluded that drying by this method is viable, with powders presenting excellent physicochemical characteristics and suitable for storage.