Abstract: Objectives: To study the experimental conditions for titrating protein content in milk powder by sodium dodecyl sulfate(SDS). Methods: The milk powder was diluted with distilled water in acidic medium, and then the diluted solution was titrated with SDS in acidic medium. At the endpoint the content of conical flask was suddenly separated into curdy white coagulum. The effects of temperature, pH, amylum, sugar and flour in the experiment were studied. The relationship between the titer of SDS soluition against the protein content in milk powder was also studied. Results: With this method the same milk powder was assayed 8 times with RSD=0.53%.The results determined by this method coincide with those of Kjieldahls method for the 8 different samples (p>0.05). Conclusions: This method is simple, accurate, dependable and suitable as rapid titration method for the determination of protein in milk powder. The time for assaying every sample is only 4 minutes.

Key words: milk powder, protein, titration, sodium dodecyl sulfate