Influence of pH on retention of camel chymosin in curd

Retained coagulant in cheese initiates casein breakdown and influences cheese structure and flavour formation. This study investigated the influence of milk pH on retention of camel chymosin in curd and compared it with bovine chymosin. Milk at five different pH levels was coagulated with same coagulant activity of each chymosin and centrifuged. Chymosin activity in whey was determined using the synthetic peptide Pro-Thr-Glu-Phe-(NO2-Phe)-Arg-Leu as substrate and HPLC analysis of the resulting product. Camel chymosin had 2.7 times lower activity in milk than bovine chymosin at the same coagulation activity. The retention of camel chymosin in curd was rather constant at similar to 20% between pH 6.65 and 6.00, while it increased almost linear from 2 to 21% for bovine chymosin. The lower pH dependence for retention of camel chymosin than of bovine chymosin may be explained by a lower negative charge of the camel chymosin molecule. (C) 2014 Elsevier Ltd. All rights reserved.