The content of protein in pure milk is about 3.0 grams per 100 ml, accounting for 3%, and the content of protein in pure milk is generally above 3%, so it can generally reach the national standard unless water is added to pure milk. Protein is the main nutrient in fat milk. Fat is now regarded as a health killer, and generally does not care whether the fat content exceeds the standard. Protein is our main nutrient. There are several detection methods for protein, each with its own advantages and disadvantages. Kjeldahl method is widely used in food industry and regarded as national standard. These are the answers found on the Internet.