Microencapsulação do extrato de beterraba por spray chilling

Abstract

Beetroot (Beta vulgaris L.) is a vegetable rich in antioxidant substances called betalains, responsible for the purplish red color. Betalains prevent or delay oxidation processes, have beneficial effects on health and are used by industries as a natural dye. As a way of reusing discarded residues and post-harvest losses, the microencapsulation of beetroot extract by spray chilling or spray at low temperatures can be considered a very viable technique. The process is based on the atomization of a mixture of the active compound and a molten lipid material in a cold chamber, where the droplets in contact with cold air solidify to form solid lipid microparticles that retain and protect the active substance. This technique has high yield, low cost, simple operation and minimizes thermal damage to the encapsulated material by using relatively low temperatures. Thus, the study aimed to take advantage of beetroot disposal and the use of the spray chilling technique, as a way to ensure the quality and stability of the final product. Therefore, three independent variables were studied: binary lipid formulations (carrier agents), containing stearic acid (EA) and oleic acid (OA), prepared in an ultrasonic homogenizer, in proportions of 50/50, 60/40 and 70/30, respectively; residence time (1, 2 and 3 min) in the homogenizer and power range (50% and 70%) of the equipment. Then, the mixtures were evaluated for kinetic stability and viscosity and, based on these results, the optimum power range and time were selected to obtain ideal colloidal systems aimed at microencapsulation of particles in spray chilling. Each treatment was evaluated by analysis of betalain content and retention, yield, morphology, color attributes, water activity, mean diameter and particle size distribution. Regarding statistical analysis, the response surface methodology was chosen to assess response patterns and determine the optimal combination of variables. Regarding the stability of the microspheres to storage, the increase in temperature and relative humidity were factors that negatively affected it. The treatments with the highest concentration of AE performed better both for lower values of ΔE* and for higher concentrations of betanin. Over the storage time, it was possible to observe greater degradation of the pigments present in the microspheres with 50/50 and 60/40 of AE/AO and, consequently, a greater visual change in color, when compared to the 70/30 treatment. With high potential for an early release and greater retention of betalains, microspheres prepared with lower concentration of AE showed potential application in refrigerated foods such as yogurts, jellies, gelatins and ice creams. The increase in AE, in addition to promoting greater particle size at higher temperatures, presented a better visual appearance, being ideal for foods that may have good melting properties in the mouth, such as chocolates, flavored milks and cake batters. In general, it is possible to develop microspheres of water-soluble compounds of different lipid concentrations from the optimization of operational methods to obtain emulsions. In addition, the spray chilling technique under the conditions of the tested operations proved to be a promising alternative for the encapsulation of beetroot extract and maintenance of its stability, which makes its application in the food industry future projects viable.