The feel-good factor associated with probiotic food and drink is stimulating the market for these products. GEA supplies the technology for the fermentation process through to producing the starter cultures and beyond to high pressure homogenization for the production of probiotic yoghurt drinks and much more.
Producing Microbial Food Cultures
Microbial food cultures (MFCs) are live bacteria, yeasts and moulds used in the manufacture of a wide range of human and animal foods: from fermented vegetable products such as sauerkraut and soy sauce, to cheese and yogurts. While starter cultures are MFC preparations which enhance the flavor, taste, color, texture and nutritional value, probiotic cultures are living microorganisms which can benefit health. But keeping billions of microbes alive and viable demands great care.
Manufacturers often want to produce individual microbial strains. Yet there are hundreds of types of probiotic and starter cultures in production, and it is important that the equipment that manufacturers use helps to avoid cross-contamination. The starting point in the production is generally a ‘mother culture’ supplied, highly concentrated, in deep-frozen form.
Fermentation Fermentation In the laboratory, this concentrate is used to make a pre-culture solution, which is in turn grown – and scaled-up – via a cultivation fermenter and a pre-fermenter to a full-scale fermentation stage operating at a capacity of several thousand litres.
After cultivation in the fermenters, the biomass has to be gently separated, under aseptic conditions, from the fermentation solution in which it has multiplied. This stage requires great care as the microbes are effective only if they remain alive. Shear stresses at the separation stage can be damaging. The concentrated cells can then be processed by freeze or spray drying and subsequent pelletizing.
The most common next step for starter cultures is freeze drying. Once frozen, the cultures can survive over long shelf lives. This enables individual cultures to be blended, at a later date, in accordance with specific starter culture recipes before final packaging.
In the case of probiotic products, manufacturers generally opt for spray dryers with fluid bed drying as the next stage. The lower the water content of the bacteria, the higher their survival rate.
In dairy applications, concentrated cultures can be fed directly from the separator into liquid nitrogen so that they are immediately deep frozen. They can then be processed into small pellets which are packaged and stored in deep frozen form.