The impact of raw material properties and process conditions on the color of a powdered formulated detergent product

The appearance of detergent powder plays an important role in consumer perception of powder effectiveness for cleaning applications. In this study, we investigated the influence of numerous formulation and processing conditions on product discoloration. Product color was scrutinized using the L*a*b* color space, and in particular, L* and b*. Particle size, the method for introducing the optical brightener, and the raw material grade were very important in controlling the optical properties of detergent granules. As the particle size decreased, the light reflected to the observer appeared brighter and bluer. This was observed as increased whiteness from L* = 84.03 with a particle size of >841 μm to L* = 90.59 with a particle size of <250 μm. Reducing the level of impurities found in the raw materials by changing the material source also improved color definition. A key finding is that the optical brightener should be applied by spraying and prepared by dispersion rather than dissolution. This improves the distribution within the granules and increases the whiteness when compared with pouring the brightener into the agglomeration vessel. Additional spray applications highlighted that brightener on the granule surface influenced whiteness more than embedded brightener. In addition, we report on the effects of the drying temperature and mixer impeller speed on powder color.