The document discusses the production of long-life milk. It describes how heat treatment through sterilization or ultra-high temperature (UHT) processing kills microorganisms and enzymes, allowing the milk to be stored at room temperature for long periods. There are two main methods - in-container sterilization, which uses batch or continuous systems to heat filled containers, and UHT treatment followed by aseptic packaging, which involves higher heat briefly before flash cooling and packaging. Proper raw materials and cleaning processes are required to ensure quality and safety of the long-life milk.

1. Long-life milk

2. • Heat treatment in the production of long-life products
is often called “sterilisation”.
• This means that the product is exposed to such
powerful heat treatment that all relevant micro-
organisms and most of the heat resistant enzymes are
inactivated.
• Such products have excellent keeping qualities and
can be stored for long periods of time at ambient
temperatures.
• Many dairies can therefore distribute these products
over long distances and thereby find new markets

3. Advantages
• advantages for the producer, retailer and consumer if a
product does not require refrigeration and can be stored for
long periods without spoiling.
• The producer can, reach geographically wider markets,
simplify production planning by reducing product changes
• Make deliveries easier by using fewer and cheaper
distribution vehicles, and eliminate return of unsold products.
• Handling becomes easier for the retailer, as expensive
refrigerated display space is not necessary and stock planning
is simplified.
• Finally, the consumer gains in convenience as he can make
fewer trips to the shops, there will be less congestion in the
home refrigerator
• have emergency reserves available for unexpected guests

4. Raw material quality

5. Raw material quality
• Milk stored for a long time at low temperature
may contain high numbers of psychrotrophic
bacteria, which can produce heat-resistant
enzymes
• Difficult to completely inactivate by heat
treatment.
• During storage they can cause organoleptic
changes such as rancidity, bitterness or even
gelation (age-thickening or sweet curdling).

6. Production of long-life milk
A . In-container sterilisation
B . Ultra High Temperature (UHT) treatment
followed by aseptic packaging
• In-container sterilisation
• Two processes are used for sterilisation in bottles
or cans.
I. Batch processing in autoclaves,
II. Continuous processing systems such as:
Vertical hydrostatic towers,
Horizontal sterilisers

7. Batch processing
• The batch system can be operated by three
methods:
1. In stacks of crates in a static pressure vessel,
autoclave,
2. In a cage that can be rotated in a static
autoclave
3. In a rotary autoclave

8. Batch processing in a static pressure
vessel (autoclave)

9. Continuous processing
• There are two main types of machine on the
market for continuous sterilisation
1. The hydrostatic vertical bottle steriliser
2. The horizontal rotary valve-sealed steriliser

10. Hydrostatic vertical
continuous bottle steriliser

11. Horizontal steriliser

12. UHT treatment

13. Various UHT systems
• The direct systems are divided into:
• Steam injection systems (steam injected into
product), Figure 9.10
• Steam infusion systems (product introduced
into a steam-filled vessel), Figure 9.11

14. • In the indirect systems the heat is transferred
from the heating media to the product
through a partition (plate or tubular wall).
• The indirect systems can be based on
Plate heat exchangers, Figure 9.12
 Tubular heat exchangers, Figure 9.13
 Scraped surface heat exchangers, Figure 9.14

16. General UHT operating phases
• Pre-sterilisation
• Hot water sterilisation at the same Temp as
the product shall undergo.
• Minimum time for the hot water sterilisation
is 30 minutes from the moment the relevant
temperature has been reached in the whole
aseptic part of the plant
Production

17. Aseptic intermediate cleaning
• The full CIP cycle takes 70 to 90 minutes and is
normally carried out immediately after
production.
• Aseptic Intermediate Cleaning (AIC) is a useful
tool in cases where a plant is not castoff used for
very long production runs.
• A 30 minute AIC can be carried out whenever it is
necessary to remove fouling in the production
line without losing aseptic conditions.
• The plant does not have to be resterilised after
AIC.

18. CIP
• The CIP cycle for direct or indirect UHT plants
may comprise sequences for
pre-rinsing,
caustic cleaning,
hot-water rinsing,
 acid cleaning and
 final rinsing,
• all automatically controlled according to a pre-set
time/temperature program.

19. Direct UHT plants
• The most effective way of achieving rapid
heating is to mix high temp steam directly
with the product, followed by flash cooling in
a vacuum vessel
• Flash cooling is an operation, which as well as
cooling, also involves deaeration and
deodorisation of the treated product

20. Direct UHT plant based on steam injection and plate
heat exchanger

22. Direct UHT plant based on steam injection and plate
heat exchanger
• product at about 4 °C is supplied from the balance
tank (1) and forwarded by the feed pump (2) to the
pre-heating section of the plate heat exchanger(3)
• After pre-heating to approximately 80 °C, the product
then continues to the ring nozzle steam injector (4).
• The steam injected into the product instantly raises the
product temperature to about 140 – 150 °C
• The product is held at UHT temperature in the holding
tube (5) for a few seconds before it is flash cooled
• Flash cooling takes place in the condenser-equipped
vacuum vessel (6) in which partial vacuum is
maintained by a pump (7).

23. Direct UHT plant based on steam injection and plate
heat exchanger
• The vacuum is controlled so the amount of
vapour flashed off from the product equals the
amount of steam previously injected.
• A centrifugal pump (8) feeds the UHTtreated
• product to the aseptic two-stage homogeniser (9)
• After homogenisation, the product is cooled to
approximately 20 °C in the plate heat exchanger
(3)
• direct to an aseptic filling machine or to an
aseptic tank for intermediate storage before
being packed.

26. Indirect UHT plants
• Indirect UHT plants are a suitable choice for
processing of milk, flavoured milk products,
cream, dairy desserts, yogurt drinks and other
non-dairy applications, such as juices, nectars
and tea

29. • The product at about 4 °C is pumped from the
storage tank to the balance tank (1) of the UHT
plant and from there by the feed pump (2) to
the regenerative section of the plate heat
exchanger (3).
• In this section the product is heated to about 75
°C by UHT-treated product, which is cooled at
the same time. The pre-heated product is then
homogenised (4) at a pressure of 18 – 25 MPa
(180 – 250 bar).

30. • Homogenisation before UHT treatment is
possible in indirect UHT plants, which means
that non-aseptic homogenisers can be used.
• However, an aseptic downstream
homogeniser might improve the texture and
physical stability of certain products that have
a high content of protein, dry matter or fat

31. • The pre-heated, homogenised product continues to the
heating section of the plate heat exchanger, where it is
heated to about 137 °C.
• Heating is performed by hot water in a closed water
curcuit.
• After heating, the product passes through the holding
tube (5), dimensioned for about 4 seconds.
• Finally, cooling is performed regeneratively in two
sequences: first against the cold end of the hot water
circuit, and then against the cold incoming product.

32. |
• If the temperature drops during production,
the product is diverted into a reject tank and
the plant is flushed by water.
• The plant must be cleaned and sterilised
before restart.