Heat sterilization causes evident viscosity change of fresh cream as well as a change in other physical properties due to heat denaturation. This experimental study shows that the viscosity changes can be summarized by using a C-value defined with the calculation method here, which is found to be commonly applicable to plate type indirect heating systems and two kinds of typical steam direct contact heating systems, showing the same tendency regardless of the heating system. It is suggested that the direct heating system is better in order to get a lower viscosity change with the same sterilization effect.