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Small-Scale

Dairy Farming Manual

Volume 1
Technology Unit 10.1
Starter Cultures
page 181

Extension Materials

What should you know about starter cultures?

What is a starter culture and why use it? (5-11)

1 A starter culture is a milk product which: 

- contains lactic acid bacteria

- controls the souring of milk. 
What types of starter culture are there? (12-20)

2 There are many types. 
Choose one for your: 

- local conditions

- the product you want to make. 
How do you prepare and maintain a starter culture? (21-36)

3 You need: 

- clean and disinfected equipment

- the correct starter culture and high quality milk 

- to do the right things at the right time. 
How can you prepare mother cultures for making cheese and yoghurt? (37-38)

4 By using different starter cultures at different temperatures. 
page 183
What is a starter culture?
5 A starter culture is milk which contains lactic aid bacteria. 
6 It changes the milk sugar (lactose) into acid (lactic acid) so that the milk becomes sour (fermented or cultured). 
Why use a starter culture?

7 To control fermentation. 
Raw milk always contains different microorganisms. 
8 These microorganisms turn your milk sour but you cannot control the fermentation. 
page 184

 
9 Pasteurization kills most of these microorganisms. 
10 By using a commercial starter culture with pasteurized milk, you can control the souring of milk 
11 and make: 

- butter 

- cheese 

- yoghurt 

and many other products. 
page 185

What types of starter culture are there?

12 There are many types of starter culture and we can group them in different ways. 
Optimum growth temperature
13 Mesophilic cultures grow best at about 30 C. 

Thermophilic cultures grow best at about 43 C. 
Physical state

14 Starter cultures can be: 

- liquids 

- solid (deep-frozen) 

- powders (freeze-dried). 
15 Powder cultures are useful because: 
- they have good keeping qualities (more than 6 months at -20 C) 
- you can send them long distances by airmail. 
page 186

 
Pure/mixed

16 Pure cultures have one species of lactic acid bacteria. 
Mixed cultures (more common) have two or more species. 
Type of lactic acid bacteria.

17 Some lactic acid bacteria produce only lactic acid. 
Others produce lactic acid gas and aromatic compounds.
Some common lactic acid bacteria used in cultures are:

Mesophilic Thermophilic
Pure Pure Mixed
Sc. lactis                Sc. thermophilus        Sc. thermophilus 
Sc. cremoris           Lb. helveticus                     + 
Sc. diacetylactis      Lb. bulgaricus            Lb. bulgaricus 
Lc. cremoris           Lb. acidophilus
 

Note:
Sc. = Streptococcus, Lc. = Leuconostoc, Lb. = Lactobacillus 
page 187

 
18 When you order, say which product you want to make.

For example:
Butter

19 You use a mesophilic culture which produces gas (carbon dioxide) and aromatic compounds (acetin and diacetyl). 
Yoghurt and soft cheese

20 You can use a thermophilic culture.
 page 188

How do you prepare a starter culture?

 Hygiene

21 Clean, sterilize and rinse with boiling water all utensils before using. 
22 Any dirt or chemicals will change the action of the starter culture. 
Equipment and materials

23 You need: 
-source of heat 
-raw milk (with or without cream) 
-starter culture powder 
-refrigerator or freezer 
24 
-pans and glass pots with lids 
-measuring breaker 
-thermos flask 
-thermometer 
-wooden spoon 
-place to maintain temperature (e.g. a hay box).
page 189

 
Preparing the milk

25 Remove the cream from high quality milk by skimming or with a hand separator. 
26 Heat treat the skim milk in a closed pot or jacket vat at 90-95 C for 30-60 minutes. 
27 Cool the milk to the inoculation temperature (see instructions on the starter culture packet.)
Preparing the culture
28 Defrost the packet 30 minutes before use.
Shake the powder to the bottom of the packet.
Disinfect the top part of the packet with alcohol before opening.
page 190

 
29 Add the starter culture to the treated milk and stir thoroughly (10-15 minutes).
You can also make the culture into a paste first with a little boiled milk.
Maturing the culture
30 Keep the culture at the correct temperature for 24 hours (see packet) by:
-using a hay box or
-wrapping in cloth in a cupboard or
-using a thermos flask.
Maintaining the culture

31 If you keep the mother culture for a long time, it gets weaker.
32 Use the clean measuring breaker to inoculate treated milk with 0.5% mother culture (5 ml culture to 1 l treated milk):
-daily if you have no refrigerator
-weekly if you have one.
page 191

 
Important points

33 The amount of mother culture for inoculation depends on the storage temperature.

Try different amounts until it works well.
34 Keep the culture in clean glass pots, not more than half full.

Take the culture from the freezer only when necessary and defrost before use.
35 The mother culture gets weak after some time.

Although it costs more, it is safer and better to use new starter culture powder after each period.
36 If you use milk powder make sure the water is boiled.

You can improve your raw milk for starter preparation by adding 2-3% skim milk powder.
page 192
How can you prepare mother cultures for making cheese and yoghurt?

Starter culture for cheese-making

37
Lyophilized Starter 
Culture (mesophilic)





Mother culture            16h at20 C
in a flask                     acidity 80-900 D=
                                     0.8-0.9% lactic acid
 

Second Mother            Starter Culture
Culture                         16h at 20 C
                                    5 l of treated milk

Third Mother               Starter Culture
Culture                         16h at 20 C
 
 page 193

Starter culture for yoghurt-making

38

 

Lyophilized Starter 
Culture (thermophilic)

Make sure that the treated milk is stable
at 45 C before adding the starter culture.
Mother culture           4h at45 C
in a flask                   acidity 800D =
                                   0.8 lactic acid
 

Second Mother           Starter Culture
Culture                       4 h at 45 C
                                   5 l of treated milk

Third Mother              Starter Culture
Culture                        4h at 45 C
 
 

 
page 194

 
What do you know about starter cultures?
       
     Starter cultures and their use
    Lactic acid bacteria in milk: 
    (5-6)
    1 Change lactose to lactic acid  
    2 Sour milk  
    Reasons for use
    1 Controlled fermentation and preservation 
    2 Production of different milk products 
    (11)
    Types of starter culture  
    Classified by:
    1 Growth temperature 
    (13)
    2 Physical state 
    3 Pure/mixed 
    (16)
    4 Type of lactic acid bacteria 
    (17)
    5 Desired product 
    Preparation and maintenance
    1 Hygiene 
     (21-22)
    2 Equipment and materials 
    3 Preparing the milk 
    4 Preparing the culture 
    5 Maturing the culture 
    (30)
    6 Maintaining the culture 
    7 Important points 
    Examples of starter cultures
    1 Cheese-making 
    (37)
    2 Yoghurt making 
     (38)
page 195

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