Optimum condition of conventional bleaching process for bleached shellac

Abstract Bleached shellac has attracted wide interest in many industries. Since bleaching using sodium hypochlorite is a vigorous process, it can possess a high impact on physicochemical properties causing the unstable bleached‐shellac. An investigation into optimum conditions of the bleaching process was, therefore, required to achieve sufficient whiteness, good mechanical properties, and the stable bleached‐shellac. The studied conditions were variations in solvents, volume, and time of bleaching. Studied parameters, such as color change, acid value, insoluble solid, polarity, water vapor permeability coefficient, mechanical properties, chemical structure, and crystallinity, were detected. The physicochemical properties depended on the bleaching conditions but no effect on the chemical and amorphous structures of shellac. With the proper control of bleaching process, the simple, and conventional method can be applied in bleaching. The optimum condition was the use of sodium carbonate as a solvent, 20‐ml sodium hypochlorite, and 2‐hr bleaching time. Practical applications Shellac has long been used as an edible coating for extending product quality. Although shellac possesses an outstanding property in moisture protection, the dark color causes an unpleasant for applying in food and pharmaceutical industries. The bleaching process using sodium hypochlorite is commonly used to whiten the shellac. Due to the vigorous redox reaction of process, extreme changes in properties of shellac were obtained. The aim was to explore the optimum condition of bleaching process. The studied conditions were, solvent used, amount, and time of bleaching process. With a careful control of process, not only provided a high degree of whiten shellac but also obtained good physicochemical properties of bleached shellac. This study could be of help in adding the value of natural polymer without the use of high temperature and power consumption compared with other methods. The bleached shellac can then be used in wider applications.