This study investigated the effect of the presence of inulin, in the range 0 - 3.81 g/100g, on the physical and microstructural properties of microparticulated whey protein concentrates (MWPC) and powders. Substitution of lactose with inulin increased levels of whey protein denaturation during microparticulation. The increased denaturation levels were correlated with reductions in lactose and calcium content of the microparticulated solutions, which increased aggregate size and solution viscosity post-processing. In conclusion, it appears possible to successfully manufacture a low-calorie microparticulated whey protein based fat replacer using the dietary fibre inulin as the carbohydrate source.