In the vat the milk is heated to 65 C and held for 30 minutes followed by rapid cooling. It is held throughout the holding period while being agitated. The milk may be cooled in the vat or removed hot after the holding time is completed for every particle. As a modification, the milk may be partially heated in tubular or plate heater before entering the vat.
If a higher temperature is used then the holding time is reduced accordingly. But the temperature is never raised beyond 68.22 C, as it causes the reduction of the cream line and induces certain undesirable physical changes.