MILK PASTEURIZATION - EVALUATION OF THERMAL-DAMAGE

Thermal damage of raw milk was evaluated during pasteurization treatme nts performed in a laboratory plant that allowed well defined thermal profiles to be established. The thermal damage of the different treatm ents, carried out at temperatures between 70 degrees and 90 degrees C and for holding times between 12.2 s and 178.6 s, was expressed as sol uble whey proteins, as extent of denaturation of each whey protein and as the ratio between the sum of the peak areas of the most thermal se nsitive whey proteins (immunoglobulin 1 and 3 + bovine serum albumin) and the total amount of beta-lactoglobulin A and B. Whey protein denat uration kinetics were evaluated obtaining the following activation ene rgy (Ea) (kJ mol(-1)) and Z (degrees C) values: Ig3 Ea = 351, Z = 6.79 ; BSA Ea = 193, Z = 12.35; beta-LGB Ea = 286, Z = 8.33; beta-LGA Ea = 224, Z = 10.64; alpha-LA Ea = 132, Z = 18.06. On the basis of Z values , the Co parameter was calculated. This allowed the different heat tre atments to be compared in terms of loss of thermolabile constituents.