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Yoghurt
types
Individual
processes
Legislation
Energy
requirements
Suppliers
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High
Temperature Short Time (HTST) method : (90-95°C for 15-40s)
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Plate heat exchanger is used - good economy of energy by using hot
milk to heat incoming milk (or vice versa) - regeneration
- compact,
simple and easily cleaned
- consists
of series of stainless steel plates mounted vertically supported
by cylindrical bars and tightly packed and sealed together
- plates
have waffle-like indentations which provide a large heat transfer
area and a turbulent flow of the liquids
-
rubber-seal
between the plates keep them 5-8mm apart
- liquids
leave the plates through holes in the corners of the plates
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open
and blind holes route the liquids to the correct plate processing
area
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- Regenerative
heating : cold milk 4-6°C is pumped to regeneration section
of heat exchanger where it is heated / warmed to 60-65°C by
heat transfer from freshly pasteurized milk ( 92% of required
heat can be recovered)
- Heating:
Milk is heated indirectly with hot water, vacuum steam or saturated
steam at atmospheric pressures to the required temperature
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Holding: The milk is held at the required temperature in
a chamber or a holding pipe - preferred. The dimensions
of the holding pipe must be sufficient to ensure the required
residence time and flow rate of the milk. The stainless
steel pipe slopes upwards and excludes trapped air. The
temperature at the end of the pipe is continuously monitored
to ensure sufficient pasteurization - if the required temperature
is not reached, the milk is returned to the heating and/or
holding sections via the flow diversion valve.
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Regenerative cooling: The hot milk from the holding section
goes to the regeneration section (1) where it is cooled to 40-60°C
by heat transfer to the incoming milk.
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Cooling: Milk is further cooled to 40-45°C, first with cold
water and finally with chilled water or refrigerant (brine or
polyalcohol solutions)
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