Starter culture

Starter culture

1. Starter Cultures Traditionally the fermenting organisms came from the natural microflora or a portion of the previous fermentation. In many cases the natural microflora is either inefficient, uncontrollable, and unpredictable, or is destroyed during preparation of the sample prior to fermentation (e.g. pasteurization). A starter culture can provide particular characteristics in a more controlled and predictable fermentation.

2. What is a starter culture and why use it? A starter culture is a milk product which: - contains lactic acid bacteria - controls the souring of milk.

3. Why use a starter culture ? To control fermentation. Raw milk always contains different microorganisms. These microorganisms turn your milk sour but you cannot control the fermentation . Pasteurization kills most of these microorganisms.  By using a commercial starter culture with pasteurized milk, you can control the souring of milk 

4. Starter Cultures Lactic starters always include bacteria that convert sugars to lactic acid, usually: Lactococcus lactis subsp. lactis , Lactococcus lactis subsp. cremoris or Lactococccus lactis subsp. lactis biovar diacetylactis . Where flavour and aroma compounds such as diacetyl are desired the lactic acid starter will include heterofermentative organisms such as: Leuconostoc citrovorum or Leuconostoc dextranicum .

5. What types of starter culture are there? There are many types of starter culture and we can group them in different ways. - local conditions - the product you want to make.

6. Types of Starter Cultures Optimum growth temperature Mesophilic cultures grow best at about 30 C. Thermophilic cultures grow best at about 43 C.

7. Types of Starter Cultures Physical state Starter cultures can be: - liquids - solid (deep-frozen) - powders (freeze-dried ) 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.

8. Types of Starter Cultures Pure/mixed Pure cultures have one species of lactic acid bacteria. Mixed cultures (more common) have two or more species.

9. Types of Starter Cultures Type of lactic acid bacteria Some lactic acid bacteria produce only lactic acid. Others produce lactic acid gas and aromatic compounds.

10. 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

11. Starter Cultures The primary function of lactic starters is the production of lactic acid from sugars Other functions of starter cultures may include the following: flavour , aroma, and alcohol production proteolytic and lipolytic activities inhibition of undesirable organisms

12. How do you prepare and maintain a starter culture? disinfected equipment, clean , sterilize and rinse with boiling water all utensils before using. Any dirt or chemicals will change the action of the starter culture. the correct starter culture and high quality milk to do the right things at the right time.

13. A good starter CULTURE will: Convert most of the sugars to lactic acid Increase the lactic acid concentration to 0.8 to 1.2 % (Titratable acidity) Drop the pH to between 4.3 to 4.5