TOS Propionato Agar Base is a medium according to ISO 29981 for the direct detection of viable Bifidobacteria. The method is applicable to milk products such as fermented and non-fermented milks, milk powders, infant formulae, and starter cultures where these microorganisms are present and viable, and in combination with other lactic acid bacteria. Casein peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is source of vitamins, particularly the B-group. Magnesium sulfate allows the detection of small numbers or injured Bifidobacteria. Ammonium sulfate acts as a nitrogen source during growth. Potassium phosphates act as a buffer system. L-Cysteine hydrochloride is the reducing agent. Transgalacto-oligosaccharide (TOS) enhances the growth of bifidobacteria used in dairy products as is an specific growth factor for all bifidobacteria whereas other lactic acid bacteria cannot utilize this saccharide. Sodium propionate inhibits the accompanying flora. The antibiotic, mupirocin lithium salt (MUP), inhibits the growth of most lactic acid bacteria commonly used in fermented and non-fermented dairy products.
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