Thermalisation |
Heating at 60–69 °C, for 20–30 s |
Death of non-heat resistance bacteria. |
No significant effect. |
Inactivation of several enzymes [4]. |
Characteristics affected by further processing [4]. |
Low Pasteurization |
Heating at 63–65 °C for 20 min/at 72–75 °C for 15–20 s (HTST) |
Death of most pathogens, vegetative bacteria, yeast and molds. |
Slight increase in viscosity and firmness [1]. |
Several enzymes denatured, denaturation of several whey proteins [4]. |
High Pasteurization |
Heating at 85 °C for 20–30 min/at 90–95 °C for 5 min |
Death of most vegetative microorganisms, except spores. |
Large increase in viscosity and firmness [1]. |
Deactivation of most enzymes. |
Denaturation of most whey proteins. |
Development of “cooked” flavor [4,18]. |
Sterilization |
Heating at 110 °C for 30 min/at 130 °C for 40 s |
Extermination of all microorganisms. |
Incorporation of whey proteins into casein matrix. Very large increase in viscosity and firmness [1,4]. |
Deactivation of most enzymes. |
Denaturation of whey proteins and aggregation of caseins (casein micelles) and MFG. |
Weakening of flavor intensity. |
Color darkening [4,18]. |
Ultra Heat Treatment (UHT) |
Heating at 145 °C for 1–2 s |
Extermination of all microorganisms. |
Medium increase in viscosity and firmness [1]. |
Mild flavor deterioration. |
Denaturation of whey proteins (β-lactoglobulin, serum albumin, several immunoglobulins) |
Development of off-flavors. |
Color darkening [4,18]. |