What is a thermophilic starter culture?
· Maryna Petruk · 3 min read
A thermophilic starter culture is a type of bacterial culture used in dairy fermentation, in particular in the production of certain types of cheese and yoghurt. The most common bacterial strains are Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Thermophilic cultures are used:
- for cheeses that require higher temperatures during production (Parmesan, Mozzarella, Swiss, Gruyère and Emmental).
- in the production of yoghurts and ryazhenka.
How does a thermophilic starter culture work?
Dry thermophilic bacteria work by fermenting lactose into lactic acid. This process lowers the pH of the milk and, as a result, causes it to curdle and form cheese. The formation of lactic acid also inhibits the growth of undesirable bacteria, helping to preserve the final product and keep it safe.
The use of thermophilic cultures affects the final product in several ways:
- Texture and taste: they produce a denser cheese curd, which is crucial for yoghurt and ryazhenka. For some types of cheese with a low second-heating temperature, thermophilic bacteria can additionally be used to regulate the intensity and direction of the lactic acid process.
- Aroma: they produce specific aromatic compounds during fermentation, which contribute to the formation of the characteristic flavour.
- Ageing: cheeses made using thermophilic cultures often require a longer ripening process at slightly higher temperatures, which allows complex flavour qualities and a dense texture to develop.
The cheese production process with a thermophilic starter culture
- Milk preparation: Fresh milk is first pasteurised or thermised and cooled to the required temperature.
- Adding the thermophilic starter culture takes place at a temperature of 37°C to 42°C, depending on the chosen product. The milk is then left for a certain time to incubate, during which the bacteria begin to ferment lactose into lactic acid.
- Coagulation: After the starter culture is activated, rennet is added to curdle the milk. A cheese curd forms, which is cut into small pieces to release the whey.
- Cooking the curd: to further separate the whey and firm up the curd, the mass is heated to the temperature recommended for specific types of cheese.
- Draining and pressing: the cheese grains are drained and placed into moulds, then pressed to remove the remaining whey.
- Salting is done by adding salt directly to the cheese, or by immersing the formed, pre-pressed cheese heads in brine. Salting helps to expel more whey, form the rind and adds flavour.
- Ripening in a controlled environment. During ripening, the thermophilic bacteria continue to work, contributing to the development of flavour and texture. Depending on the cheese variety, ageing can last from several months to several years.
Recommendations for storing and using thermophilic starter cultures
- Store frozen (-45°C) or freeze-dried (-18°C). Make sure the cultures are kept in airtight containers to prevent exposure to moisture and contaminants.
- It is important to follow the manufacturer's instructions on dosage and coagulation time. It is very important to add the culture to milk that has been heated to the correct temperature range (37°C to 45°C). Adding the culture to milk that is too hot or too cold can inhibit bacterial activity.
- Always use clean, disinfected equipment to prevent contamination. Observe sanitary and hygiene requirements when adding starter cultures to milk.
Prodservis offers a wide selection of starter cultures from the well-known French manufacturers Bioprox and Biovitec. Thanks to our starter cultures, you can always be confident in the quality of your final product and its standardisation from batch to batch.
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