Determination of the protein content of milk according to the amido black method using the Pro-Milk-Automatic instrument
Thomasow, J.; Mrowetz, G.; Delfs, E.-M.
Milchwissenschaft 26(8): 474-481
The reproducibility, accuracy and range of applications of the Pro-Milk-Automatic instrument were systematically tested. Reproducibility of readings was +or-0.005%, deviation from protein determined by Kjeldahl, +or-0.024% for mixed milk and +or-0.05% for individual milks. Preservation by 0.2% K2Cr2O7 lowered readings by 0.01% protein, a figure which remained unchanged for 15 days in the absence of coagulation. Compensation therefore was obtainable by adjustment of the instrument. Pasteurization of samples did not affect results, UHT treatment lowered them by 0.03%, sterilization by 0.15-0.20% and condensation rather erratically. The instrument is operationally reliable and provides a rapid and accurate method for the determination of protein in raw, preserved or pasteurized milk.