What is a starter culture?
A starter culture is a bacteria culture that you can use to manufacture fermented milk products such as yoghurt, kefir, cheese, and butter among many other cultured dairy products.
You inoculate (“seed”) the starter culture into the milk/dairy product and allow it to grow/multiply under controlled conditions. This controlled environment will allow the bacteria to multiply and impart the characteristic features of the resultant cultured dairy product such as acidity (or pH), aroma, consistency, and flavor.
Bacteria break down lactic acid in the dairy product, resulting into increased acidity (or low pH). The low pH imparts a preservative effect to the product and improves its nutritive and digestive quality.
What makes up a starter culture?
Different dairy products have different qualities and distinctive characteristics, which are dependent on the type of culture you use to make that specific product. The cultures may contain a pure strain of bacteria (single strain) or multiple strain type (with many species of bacteria; each strain has its specific role to play in the mixture).What are D, L, and DL Cultures? #startercultures #yoghurt #cheese Click To Tweet
Some starter culture bacteria only ferment lactose into lactic acid. Such strains include Streptococcus lactis, Streptococcus cremoris, and Streptococcus thermophilus. They are majorly used to make acidified dairy products. Other strains such as Streptococcus diacetylactis and Leuconostoc citrovorum produce flavor and aroma as well.
About D, L, and DL cultures
Starter cultures that contain the three stains of Streptococcus lactis, Streptococcus cremoris and Streptococcus diacetylactis to produce both acid and flavor in the dairy product are classified as D cultures (D is for the diacetylactis).D cultures contain Strep. lactis, Strep. cremoris and Strep. diacetylactis #startercultures Click To Tweet
On the other hand, if you opt to use Leuconostoc citrovorum to produce the aroma and flavor in the dairy product, you will end up with an L culture (L is for the leuconostoc).
A combination of both D and L cultures produces a DL culture, which has the qualities of all the bacteria used.
- D culture: – contains Streptococcus lactis, Streptococcus cremoris and Streptococcus diacetylactis
- L culture: – contains Streptococcus lactis, Streptococcus cremoris and Leuconostoc citrovorum
- DL culture: – contains Streptococcus lactis, Streptococcus cremoris, Streptococcus diacetylactis and Leuconostoc citrovorum
List of bacteria present in the starter culture
|Bacterial strain||What it does||Used to make|
|Propionic bacterium shermanii||Flavor/aroma, eye formation||Emmental cheese|
|Lactobacillus bulgaricus||Acidity, aroma/flavor||Kefir, yoghurt|
|Lactobacillus acidophilus||Acidity||Acidophilus milk, cultured milk|
|Streptococcus thermophilus||Acidity||Yoghurt, cheddar and emmenthal cheese|
|Streptococcus diacetylactis||Acidity, flavor/aroma||Butter, cultured cream, cultured milk|
|Streptococcus lactis, Streptococcus cremoris||Acidity||Cheese, butter, cultured cream, cultured milk|
|Leuconostoc citrovorum, Leuconostoc dextranicum||Flavor/aroma||Cheese, butter, cultured cream, cultured milk|
|Streptococcus durans, Streptococcus faecalis||Acidity, flavor/aroma||Cheddar cheese, Italian soft cheese|
Symbiotic Relations of Starter Culture Bacteria
Some Streptococcus diacetylactis bacteria produce concentrated acid in the product that they do not need the help of Streptococcus lactis/Streptococcus cremoris in acidifying the culture. The bacterial strains are combined because they have a mutual benefit in the culture.
For instance, Leuconostoc citrovorum needs the nutrients (metabolites) produced by Streptococcus lactis/Streptococcus cremoris for its growth. It means that if you eliminate these, the Streptococcus citrovorum will not grow properly in the culture.
The slow growth in the acid-less environment will affect aroma production. Consequently, the quality of the final product will not be consistent. You will fail to achieve a similar product as the one you produce in the presence of acid-producing bacteria.
Bacterial tolerance towards temperature, pH, or salt concentration in the medium affects the products you produce. Control the process to produce the results you want.
The purpose of mixing the strains is to impart the symbiotic advantages to the culture. This will reduce competition among the bacteria in the starter culture. The bacteria characteristics are to complement one another in the process of product formation.
The table below lists some of the tolerance levels for the culture bacteria
|Bacterial strain||Optimum temp (°C)||Max % salt tolerance||% acid formation||Ferments citric acid (- no; + yes)|
|Str. lactis||About 30||4-6.5||0.8-1.0||–|
|Str. diacetylactis||About 30||4-6.5||0.8-1.0||+|
Where do people get starter culture if they want to make fermented dairy products
Various laboratories that specialize in manufacturing starters make special cultures for the production of the various dairy products. These starters can be obtained by special orders form the manufacturers or their vendors. These cultures have been specially mixed to produce the desired effect on the processed dairy products.