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Proteolysis of goat beta-casein by calf rennet under various factors affecting the cheese ripening process
- Trujillo, A.J., Guamis, B., Carretero, C.
- Journal of agricultural and food chemistry 1995 v.43 no.6 pp. 1472-1478
- goat milk, beta-casein, proteolysis, rennet, calves, temperature, pH, sodium chloride, cheese ripening, polypeptides, electrophoresis, pepsin, chymosin
- The proteolytic activity of calf rennet on goat beta-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; beta-I-beta-V, in order of appearance and increasing electrophoretic mobility under alkaline conditions. In an aqueous solution, beta-casein was optimally hydrolyzed to beta-I at pH 6.2, beta-II at pH 3.8, and beta-III at pH greater than or equal to 5.4. beta-IV products were formed at all pH values, and beta-V was optimally formed at pH less than or equal to 5.0. Both beta-IV and beta-V were formed in very small quantities. Proteolysis of beta-casein by calf rennet is reduced by the addition of 5% Nace, while the addition of 15% Nace leaves only traces of beta-I. The polypeptides beta-I, beta-II, and beta-III produced from caprine and bovine beta-caseins gave identical results with PAGE, which suggests that the calf rennet attacks the same regions described as susceptible to bovine beta-casein cleavage by chymosin.