Without them, we would have no cheese, no yogurts... they work around the clock and perform real miracles: lactic acid bacteria. Many do not know what it is that they do exactly.
Lactic acid bacteria – Lactobacillus, Streptococcus, Lactococcus and Leuconostoc – are unimaginably small. One lactic acid bacterium measures just one thousandth of a millimetre. This is why there is such a huge number of them. One spoon of yogurt contains tens of millions of lactic acid bacteria.
Lactic acid bacteria is necessary for the manufacture of cheese, yogurt and quark (curd cheese). Just like people, they have a bit of a sweet tooth and gain energy for their metabolism from lactose (milk sugar). Depending on the kind of cheese or yogurt, different bacteria – also known as cultures – are used.
The choice of cultures determines whether a cheese or yogurt is made. In the case of cheese, the lactic acid bacteria are combined with milk and rennet in the cheese maker. However, they only begin to work once the correct temperature has been reached. Each lactic acid bacterium has a different preferred temperature. For semi-hard and hard cheese, bacteria is used that requires a temperature of around 30°C to 35°C. For yogurt, things get a bit hotter: these bacteria cultures prefer temperatures of between 35°C and 45°C.
From sugar into acid
Once they have been brought to life, the bacteria “nibble” at the large lactose molecules, triggering the start of what is effectively a digestive process. In doing so, they break the sugar down into acids. The result? The pH value falls from 7 to around 4 to 4.5. Once the target pH value has been reached, the product is cooled. This prevents the bacteria from having any further effect.
The low pH value has the advantage of ensuring that unwanted micro-organisms are rendered harmless. Milk is therefore made long-lasting in the form of cheese, yogurt or quark.
If cheese is cooled and put into a salt bath, the bacteria go to sleep and stop multiplying. Later, when the cheese is put into storage in the cellar, other bacteria are woken which are responsible for maturing the cheese. These produce enzymes that set about breaking down the milk proteins, giving the cheese its typical taste, aroma and consistency – or curd characteristic.
The utmost secrecy
The composition of bacteria cultures is subject to the utmost secrecy. There are many factors that make milk into a well-processed product – the quality of the milk, other ingredients, the production processes, and so on. However, the micro-organisms play a crucial role here and the key is finding the optimum bacteria combinations. There are countless ways to combine bacteria with one another in different proportions.
Lactic acid bacteria not only play a key role in cheese, but also for fresh products such as Benecol and Aktifit: lactic acid bacteria are added to both these drinks and release their beneficial properties only once in the body, which can help with digestion.