Small-Scale

Dairy Farming Manual

Volume 1

Technology Unit 4
Milk Preservation


page 69




 
Extension Materials

What should you know about milk preservation ?

What is important in 
preserving milk ? (5-7) 

1 It is important to make sure that your milk is: 
- clean 
- cool 
- delivered quickly 

Why cool your milk ? (8-25) 

2 Keeping your milk cool 
reduces damage.

Why heat treat and process your milk ? (26-29 

3 Heat treatment kills bacteria and your milk keeps longer. 
Processed products like cheese  keep longer too 

Can you use chemicals to preserve your milk ? (30-49) 
 

4 Yes, but you must ask your extension worker 

or milk collecting centre for advise

 page 71


5    All of the ways of preserving milk depend upon the initial hygenic quality of your milk.

Make sure everything is clean
and you cattle are healthy.

6    Do not mix warm (morning) milk
with cool (evening) milk.

Keep it separate for the collecting centre
or cool warm milk before mixing.

7    Whatever method of preservation you use,
plan with farmers near you
and your collecting centre
to deliver the milk
in the shortest time possible.
page 72

Why cool your milk?

 8    If everything is clean and you and your cow are healthy, your milk will be:
- fresh

- good quality

- quite stable.

9    When you store or transport your milk
many things can damage it:
- chemicals
- bacteria
- bad handling.
10    If your milk is warm,
there will be more damage from chemicals,
bacteria and bad handling.
11    Temperatures between 15-40 C are bad for milk.
There is high enzyme activity and bacteria multiply quickly.

page 73



 
12    Keeping your milk cool reduces damage.

About 4 C is the best temperature to keep milk.

13    If you can deliver your milk
within one to two hours
and the milk collecting centre
has good cooling facilities,
cooling your milk at home is not essential.
How long can you keep your milk?
14    This depends on the:
           Temperature                   and                  hygiene
oC
Very clean milk
Clean milk
Dirty milk
4

10

20

35

good quality

good quality

poor quality

bad quality

good quality

bad quality

turned bad

turned bad

poor quality

very bad quality

turned bad

turned bad

page 74

15    You can keep your milk
 

in the shade or
in a dark, well-ventilated place.

16    You can put your milk cans in a well.

If you use the water for drinking, be careful it does not become dirty.

17    Make sure the tops are tight or cover with cloth so that water from the well does not get into your milk.
page 75

You can use cooling tanks

18    If you have a good supply of water, put your cans into a cooling tank.
The temperature of your milk is 3-5 C above the temperature of the water (after some time in the water).
Milk oC
 Water oC
7
 3
10 
6
13
 9
16
12
 
19    For large quantities of milk,

pass cool water
through a double envelope.
 
 
 

 

20    If ice is available,
 

you can use it for cooling your milk.

21    Loosen the lids of the cans to allow the air to escape.

Make sure no water gets into the milk.

Cover the cooling tank with a lid to protect the milk from insects and dust.

page 76

You can use cooling rings

22    If cool (10 C or less) running water is available,
you can pass it through a perforated ring so that it flows over the cans.
23    If you have a big farm
(400-500 l milk/day),
use a mechanical farm 

cooling tank
which runs on electricity.

You can use ice cones

24    If you send small amounts of milk
a long way,

you can use ice cones.

Fill the cones with crushed ice
and place in the milk.

 25    Clean the cones
carefully after use
and again before use.
page 77

Why heat treat your milk?

26    If you heat your milk
before storing,
you kill many bacteria,
so you can keep your milk longer.
27  Thermatisation
 

is low heat treatment.

As soon as possible
after milking
heat your milk to 65 C.

28    Then cool down
as fast as possible
to under 10 C.
(See T.9 Milk Treatment)

Why process your milk?

29    For quick local consumption,
you can preserve your milk
by processing it into products such as:
- cheese
- curd
- pasteurized milk
- yoghurt.
(See T.10 Milk Production Manufacture)
page 78

Can you use chemicals to preserve your milk?

30    Yes, but the milk collecting centre
should advise you
because you need to use
the correct types and
amounts of chemicals.
31    Only use chemicals in your milk if you cannot cool it.

Heat treat your milk or
deliver to a collecting centre
quickly after milking.

32    Only use chemicals
in the milk you deliver
to a dairy plant.

Do not use chemicals
if you drink your own milk or
if you deliver your milk to
anywhere but a dairy plant.

33    The dairy plant will

process your milk
so that the chemicals
are not harmful.

page 79

Is it legal to use chemicals?
34 You must check
if the use of chemicals
is legal in your country
 Do chemicals make your milk clean?
35  No,
you cannot change
poor quality milk
into good quality milk
by using chemicals.
36    Good quality milk comes from

hygiene and

healthy animals.

37
 
 

- keeping your milk cool
and handling it gently.
 
 
 

 

page 80

Why use chemicals to preserve your milk?

38    You can keep
 

uncooled milk longer,
even in high temperatures.

39    You can keep cooled milk longer and therefore,
reduce the numberof deliveries.
40    You can deliver milk
which spoils and the dairy plant rejects if you do not use chemicals.
41    If you use chemicals correctly, they have little effect on the physical quality of the milk.
page 81

How can you use hydrogen peroxide to preserve your milk?

42    Add the correct amount of liquid hydrogen peroxide or solid carbamide peroxide to your milk.

Important

Ask your extension worker or dairy plant to advise on adding chemicals to your milk.
43    The dairy plant 
gets rid of the peroxide
by adding the correct amount of catalase to your milk.
44    You can preserve your milk from 6 to 24 hours
in tropical temperatures
if your milk is good quality
in the first place.

page 82


How can you use the lactoperoxide system to preserve your milk?

45 Within 2-3 hours of milking:

- add 14 mg of sodium thiocyanate for each litre of milk
- stir well
- add 30 mg of sodium
percarbonate for each litre of milk
- stir well.

Important
Add the chemicals in the correct order.
46    You can keep your milk
for up to the following times:
 
 
 
Temperature (C)
Time (hours)
25 - 30
8
20 - 25
12
15 - 20
18
10 - 15
30
4
48
 
page 83

Remember
47    Use only the right amounts of the right types of chemicals.

Consult
your milk collecting centre.

48    Make sure you get
 
 

new chemicals often.

Always check
the instructions on the label.

49    Keep all chemicals
out of reach of children
and animals
and away from
food and drinking water.
  page84


 
What do you know about milk preservation?
     
    Important factors
    1.   Hygiene 
    2.   Temperature
    3.   Quick delivery 
    Reasons for cooling milk
    Cooling milk reduces:  
    1.   damage
    2.   enzyme activity and rate of increase of bacteria 
    Keeping time 
    Depends on:
    1.   temperature
    2.   hygiene
    Methods of cooling milk
     1.   Traditional:
         - shade 
         - well 
    (16)
    2.   Cooling tanks 
    3.   Cooling rings 
    4.   Ice cones 
     Heat treatment
    1.   Reason: kill bacteria 
    (26)
    2.   Thermatisation 
     Processing 
    (29)
    Use of chemicals
    1 When to use chemicals 
    2 Legality
    3 Limitations 
    4 Reasons for use 
    5 How to use hydrogen peroxide 
    6 How to use the lactoperoxide system 
    7 Points to remember

page 47