Summaryβ-Casein is highly resistant to proteolysis in Cheddar cheese. A decrease in NaCl concentration reduced its resistance, but even in the absence of salt the amount of proteolysis of β-casein was slight. Proteolysis in Cheddar cheese increased when the moisture levels were raised by adding water. The relative susceptibility of β-casein to proteolysis by rennin was reduced considerably when the concentration of a sodium caseinate solution was raised from 10 to 20%. Sequestering the Ca2+by means of EDTA had no significant effect on proteolysis of β-casein. It would appear that the resistance of β-casein to proteolysis is due to the substrate rather than the enzyme and it is suggested that the reduced relative susceptibility to proteolysis is due to some concentration-dependent physical change in the casein molecule which renders the β-casein inaccessible. The salt concentration would also appear to influence this change.Cheddar-cheese flavour is largely independent of rennet concentration and it is possible to manufacture cheese of satisfactory quality using half-normal rennet levels.
The percentage of milk fat recovered as cheese varies between 85 and 93 per cent, depending on the system used, and this must be taken into account when the casein to fat ratio of milk for cheesemaking is selected. Seasonal variation in the composition of milk protein can have a significant influence on the potential cheese yield. Prolonged storage of milk may cause casein losses while heat precipitation can facilitate the incorporation of whey proteins in cheese curd. The economic consequences of seasonal variations in Ireland on the price of milk for cheesemaking are discussed. The economics of standardisation may be marginal, but it is a useful aid in achieving uniform cheese quality.
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