90% protein content refers to the natural form of whey protein isolate as a raw material (not our Natural "flavour"). In our finished product of WPI 90, the protein content will vary depending on the input of any additional ingredients - such as natural flavours - which will slightly reduce the overall protein content. Natural flavour has the highest protein content at 89g per 100g, while the rest have a protein content ranging from 77g to 85g per 100g. Based on the nutritional information, you can make an informed choice on the protein supplement that suits you best.