Furthermore, the heat stability in skim milk (0.3% fat, home brand, Netto supermarket) was tested in the same manner at 70, 80 and 90 °C. Before the residual peptidase activity was determined, 0.8 mL of each sample was brought to 2.5 mL with 50 mm MOPS buffer (pH 6.7) and desalted using PD-10 columns, according to the manufacturer's protocol (GE Healthcare, Munich, Germany).