DAIRY PROCESSING:Heating

Milk should be heated to 63°C for 30 minutes to adequately pasteurise it or, if in bottles, to 121°C for 15-20 minutes to adequately sterilise it. Higher temperatures and shorter times are used in larger commercial operations but this type of equipment is very expensive and is not considered to be 'small-scale'.
Pasteurisation can be done in open pans with continuous stirring, then filling the milk into pre-sterilised bottles (100°C for ten minutes in steam or water) and sealing immediately. Sterilisation requires the use of a pressure cooker to achieve 121°C at 104 kPa (15 psi ) which increases the capital cost of processing. Milk is filled into bottles which are then sealed and placed in the pressure cooker. The temperature and pressure are gradually raised and lowered to give the correct processing time. Sterilised milk has a shelf life of several weeks/months if unopened but extreme care is needed to ensure adequate heating in order to prevent food poisoning. This is not recommended for inexperienced processors.


Boiling milk to evaporate some of the water and produce a brownish gel is a low technology process which produces a snack food/sweet popular in some parts of Asia. The product has a shelf life of a few weeks and may be used in other foods or have ingredients such as sugar, colour, spices, fruits and nuts added to give variety.