Proteolysis of Goat β-Casein by Calf Rennet under Various Factors Affecting the Cheese Ripening Process

The proteolytic activity of calf rennet on goat β-casein was studied under various technological parameters which affect cheese ripening (temperature, pH, salt and calf rennet concentrations). Electrophoretic studies showed that this protein hydrolyzes to give five products; β-I-β-V, in order of appearance and increasing electrophoretic mobility under alkaline conditions. In an aqueous solution, β-casein was optimally hydrolyzed to β-I at pH 6.2, β-II at pH 3.8, and β-III at pH ≥5.4. β-IV products were formed at all pH values, and β-V was optimally formed at pH ≤5.0. Both β-IV and β-V were formed in very small quantities. Proteolysis of β-casein by calf rennet is reduced by the addition of 5% NaCl, while the addition of 15% NaCl leaves only traces of β-I. The polypeptides β-I, β-II, and β-III produced from caprine and bovine β-caseins gave identical results with PAGE, which suggests that the calf rennet attacks the same regions described as susceptible to bovine β-casein cleavage by chymosin. © 1995, American Chemical Society. All rights reserved.