# Advances in the Application of Microcapsules as Carriers of Functional Compounds for Food Products
## 5 Recent Advances in the Stabilization of Bioactive Compounds  
Over the past five years, researchers have shown great interest in using spray-drying, freeze-drying, and coacervation techniques using different wall and core materials. Wall materials, such as maltodextrin and arabic gum, and core materials, such as probiotic bacteria, phenolic compounds, and carotenoids were some of the most widely used materials (Table 1). The stabilization of carotenoids from fruit juices (carrot and tamarillo) was performed by spray-drying in studies comparing the influence of different wall materials (arabic gum and maltodextrin) on chemical and physicochemical properties of the microcapsules [32; 33]. The authors observed that arabic gum particles presented greater carotenoid retention and encapsulation efficiency when compared to the maltodextrin ones. Furthermore, [PERSON] et al. [32] also analyzed the storage stability of the microcapsules in relation to their antioxidant activity and the amount of carotenoids retained under different storage conditions. It was observed that powders produced with arabic gum stored at 25 \({}^{\circ}\)C for 24 days had a higher rate of carotenoid degradation than powders produced with maltodextrin. This fact was attributed to a higher rate of water activity at the beginning of the storage period, being more susceptible to degradation of the compounds and loss of antioxidant activity. Another microencapsulation technique that has been used to stabilize carotenoids is complex coacervation. [PERSON] et al. [52] and [PERSON] et al. [21] studied the stabilization of carotenoids from sea buckthorn by microencapsulation using whey protein isolate as wall material. In both works, the authors suggest that the wall material used is a capable matrix for the encapsulation of carotenoids, presenting encapsulation efficiency varying between 41% and 56%. Also, laser confocal scanning microscopy confirmed that carotenoids were within the coacervates produced. Overall, the authors recommend that the microcapsules produced in the study have potential for use in the food industry as a natural source of antioxidants. [PERSON] et al. [38] evaluated the effect of different combinations of wall materials (maltodextrin/ arabic gum, maltodextrin/gelatin, maltodextrin/chitosan and maltodextrin/\(\beta\)-cyclodextrinurin/ arabic gum) on microencapsulation of plum phenolic compounds by spray drying. Encapsulation efficiency and storage stability of the microparticles were assessed. According to the authors, the stabilization of plum phenolic compounds was successfully achieved for all combinations of wall materials used. However, microcapsules produced with maltodextrin/chitosan showed higher retention of phenolics, above 94%, during storage for 60 days at 25 \({}^{\circ}\)C, compared to other microcapsules (between 80% and 90%) and to non-encapsulated phenolics (31%). Additionally, it was observed that the microcapsules with a smooth external surface demonstrated better protection of the phenolic compounds. Overall, the authors concluded that microcapsules produced with different wall materials improved the stability of phenolic compounds, presenting a potential for the commercial application of plum phenolics as nutraceutical products. Natural and synthetic extracts of vanilla rich in polyphenols were microencapsulated by spray-drying using whey protein concentrate as a wall material [42]. The microcapsules produced from each core material were compared and analyzed for their physicochemical properties, antioxidant activity, and vanillin retention during storage. No significant differences were found in the physicochemical properties studied (moisture, water activity, color, hue angle, solubility, microencapsulation yield, bulk density) for either type of microcapsule produced. The microcapsules showed higher preservation of vanillin when compared to the non-encapsulated extracts during storage for 30 days at 25 \({}^{\circ}\)C, showing to be a good strategy for its stabilization.