Stabilization of Chinese Gallnut (Galla Chinensis) Tannins by Spray-Drying Microencapsulation for Natural Hair Coloring

Abstract

Chinese gallnut (Galla chinensis) is rich in hydrolyzable tannins, which, when mordanted with ferrous ions, produces intense black color on keratinous fiber and makes it a desirable natural hair dye in Asian countries. However, extracted tannins from Chinese gallnut are susceptible to chemical degradation by physicochemical factors (heat, UV, and high pH) that limited the utilization and commercialization of this plant colorant in color cosmetics. Hence, this study was aimed to improve the storage and application stability of Chinese gallnut extract by spray-drying microencapsulation. Different combinations of maltodextrin (MD) and gum arabic (GA) were used as encapsulating agents and the effects on the encapsulation efficiency, morphology, physicochemical properties, in vitro toxicity, and stability were investigated. The results showed that an increase of MD proportions in the wall matrix resulted in the production of more spherical shaped particles with larger size, decreased bulk density, and improved solubility in water. Furthermore, microcapsules covered with MD alone showed the maximum stability with respect to heat, UV, and formulation at alkaline pH. When applied for dyeing of human gray hairs, intense black color could be achieved by using the MD-covered microcapsule formulations and the dyeings are stable to multiple washings and simulated sunlight. Therefore, this study examines a promising strategy for stabilizing tannin-rich extract from Chinese gallnut while maintaining its dyeing efficiency, which will in turn promote its utilization in hair coloring cosmetics.