Bifidobacteria cultures as components of yoghurt-like products.

Abstract

Bifidobacteria species or subspecies in cultured or culturecontaining milks is a presently approved way to offer beneficial effects for human health. The microorganisms should be still in a living stage at the time of consumption. Multiplication and viability of the anaerobic Bifidobacteria in milk require special efforts in production, handling and storage of this kind of products. It is possible to maintain the viability of Bifidobacteria in culture-containing milks, as there is no remarkable lowering of pH during shelf life. In cultured milks, however, (yoghurt-like products) the viability of Bifidobacteria is reduced to a higher degree, depending on the extent of acidification and the strains used. The range of decrease of colony-forming units (cfu) of 3-4 log10 cycles may occur within 20 or even 5 days. There may still be some unknown facts concerning the irregular curve of counts. The survival of Bifidobacteria means living cells from ingestion should reach the adequate area of the intestinal tract of humans. That is still not verified sufficiently. Results from animals cannot be transferred to humans without limitations. Knowledge on humans is based mostly on well-founded suppositions and may be confirmed experimentally in more detail in the future. The identification of Bifidobacteria in milks is not too difficult in principle. Species which are used can be identified in a quite simple way, such as Bifidobacterium longum, breve, infantis, or even bifidum. Some difficulties may result with separation of Bifidob longum from Bifidob. animalis. Problems with isolating Bifidobacteria from milks may arise if a dominating lactic acid bacteria flora is present. No full selective media seems to have been explored up to now. Bifidobacteria counts lower than 104/g may not be determined if total count comprises more than 108/g.