The effect of exposure to pressure of 50 MPa on Cheddar cheese ripening

The possibility of acceleration of commercial Cheddar cheese ripening by exposure to a high pressure (HP) treatment of 50 MPa for 3 days at 25°C at different stages of ripening was investigated. Proteolysis was examined in the treated and untreated cheeses by measurement of pH 4.6 water soluble nitrogen, expressed as g/100 g total N (pH 4.6 SN/TN), urea-PAGE, reverse phase (RP) HPLC, analysis of molecular mass distribution by gel permeation and measurement of free amino acids (FAA) in the pH 4.6 SN. There was an immediate increase in pH 4.6 SN/TN and FAA in cheese HP-treated at 2 days of age, although this effect decreased with cheese age. Urea-PAGE analysis of cheese samples indicated that HP treatment accelerated degradation of αs1-casein and accumulation of αs1-I-casein (f 24-199). RP-HPLC profiles indicated quantitative but not qualitative differences between treated and non-treated samples. Confocal laser scanning microscopy did not indicate any gross structural changes in the cheese matrix as a result of exposure to 50 MPa for 3 days at 25°C. It was concluded that the enhancement of proteolysis observed may be attributed to a combination of the temperature and pressure used in the treatment.