Milk Reception, Chilling, Storage and Transport
Milk Reception, Chilling, Storage and Transport tests the cold chain from tanker intake to processing. The exam expects sequence, temperature limits and the reasons behind each step.
Reception sequence
At reception, check the tanker seal and temperature, sample after agitation, test smell, acidity, fat, SNF and adulterants, weigh or measure volume, then filter/clarify and chill. Reject milk with antibiotic residues, high acidity, off-flavour or abnormal colour. Do not mix suspect milk with accepted milk.
Chilling and storage
Cool raw milk rapidly to 5 C or below and hold at 4-5 C with mild agitation. Low temperature slows bacterial growth but does not stop lipase, which can cause rancidity. Insulated tanks and tankers must be cleaned and sanitised. Avoid unnecessary agitation, air incorporation, light exposure and temperature fluctuation.
Worked example
10,000 L milk at 35 C is chilled to 4 C. Take density 1.03 kg/L and specific heat 3.93 kJ/kg·K. Mass = 10,300 kg; ΔT = 31 K. Heat removed = 10,300 × 3.93 × 31 = 1.25 × 10^6 kJ. If removed in 2 h, average load = 1.25 × 10^6 / 7,200 s = 174 kW. This shows why pre-cooling at the farm reduces reception chilling load.
Traps
Do not add warm milk to a cold tank without checking capacity and temperature. A low temperature does not make unsafe milk acceptable. Do not sample before agitation; fat may be uneven. Do not assume chilling stops all enzyme activity or all bacterial growth.