Ascorbic acid particulates are simultaneously milled and coated with wax in this study using a novel process based on fluid energy milling. A premix of ascorbic acid particulates and wax powders are fed into a fluid energy mill, inside which ascorbic acid particulates frequently collide with each other and with wax powders. Consequently ascorbic acid particulates are broken down to smaller sizes and coated with wax simultaneously. This simultaneous milling and coating process has several advantages compared to traditional separated milling and coating processes such as dramatically improved production efficiency, elimination of solvent usage and prevention of particle agglomeration. The wax coating slows the dissolution rate of ascorbic acid in water, especially when the wax content passes certain threshold value.