In an HTST milk pasteurizer, if the milk temperature measured at the end of the holding tube falls below the legal set-point ($72^\circ\text{C}$), the Flow Diversion Valve (FDV) automatically operates by:
Options:
(A) Diverting sub-pasteurized milk back to the raw milk balance tank for re-pasteurization
(B) Shutting off the boiler steam valve immediately
(C) Increasing the speed of the milk timing pump
(D) Injecting cold water directly into the milk stream
Answer Key:
A
Step-by-Step Solution & Explanation
The Flow Diversion Valve (FDV) is a solenoid-pneumatic fail-safe valve at the exit of the holding tube. When temperature drops below $72^\circ\text{C}$, the valve instantly diverts unpasteurized milk back to the balance tank to prevent improperly treated milk from reaching downstream cooling sections.