AbstractEffect of extrusion (120 °C; 8–12 s; extruder S 45‐12‐10 U) on amino acids and nutritive value of casein preparations in the form of calcium and low‐calcium paracaseinates and in acidic form was studied. The following indices were found to decrease slightly: chemical score (CS) from the range 57.4–58.8 to 57.2–58.1; essential amino acids (EAA) from 86.1–88.3 to 84.9–88.1; NPU from 61.4–67.6 to 60.2–66.6; PER from 2.40–2.47 to 2.38–2.45; apparent digestibility (AD) from 84.9–87.2 to 84.8–87.2; true digestibility (TD) from 90.7–95.3 to 90.4–92.8 and biological value (BV) from 66.6–71.0 to 65.8–69.6. These results prove that the extrusion at 120 °C does not result in a significant lowering of the prote