UHT Processing Calculations

Step 1: Time in hold tube

Flow rate through hold tube, Q_flow = gallons per minute

Length of hold tube, L_tube = feet

Inside diameter of hold tube, d_tube = inches

V_max/V_av = (Typical values: Laminer flow - 2.0; Turbulent flow - 1.2)

Hold time = 11 sec

Step 2: D-value at Processing temperature

Processing Temperature, T = ^oF

D-value at Reference Temperature, D_ref = sec

Reference Temperature, T_ref = ^oF

Z-value = ^oF

D-value at processing temperature, D_T = 0.93 sec

Step 3: Lethality

Total microbial reductions, Log(N/N₀) = 12

Assumptions:

Coldest place in the product flow is usually at the center of tube.
Microbial inactivation follows first-order kinetics.
Lethality described here (in Step 3) corresponds to hold-time stage only. Microbial deactivation corresponding to heating and cooling stages are not considered here, making this computation a conservative estimate of lethality.

UHT Processing Calculations

Step 1: Time in hold tube

Step 2: D-value at Processing temperature

Step 3: Lethality

Assumptions:

Mathematical equations for UHT calculations