Thermal Processing and Sterilization

In an HTST regenerator, raw milk enters at $T_{in} = 4^\circ\text{C}$ and is preheated to $T_{reg} = 65^\circ\text{C}$ before entering the final heating section to reach pasteurization temperature $T_{past} = 72^\circ\text{C}$. Regeneration efficiency is $\eta_{reg} = \frac{T_{reg} - T_{in}}{T_{past} - T_{in}} \times 100 = \frac{65 - 4}{72 - 4} \times 100 = \frac{61}{68} \times 100$. The regeneration efficiency in percentage (rounded off to one decimal place) is: