Dairy Farming Manual
What should you know about starter cultures?
|What is a starter culture and why use it?
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?
2 There are many types.
- local conditions
- the product you want to make.
|How do you prepare and maintain a starter
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.
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?|
|8 These microorganisms turn your milk sour but you cannot control the fermentation.|
|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:
and many other products.
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.
- 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.
|Type of lactic acid bacteria.|
|Some common lactic acid bacteria
in cultures are:
|18 When you order, say which
product you want to make.
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.
How do you prepare a starter culture?
|22 Any dirt or chemicals will change the action of the starter culture.|
|Equipment and materials|
-pans and glass pots with lids
-place to maintain temperature (e.g. a hay box).
|Preparing the milk|
|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.
|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|
|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.
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
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.
How can you prepare mother cultures for making cheese and yoghurt?
Starter culture for cheese-making
16h at20 C
Starter culture for yoghurt-making
Make sure that the treated milk is stableMother culture 4h at45 C
at 45 C before adding the starter culture.
in a flask acidity 800D =
0.8 lactic acid