INFLUENCE OF AGAR-AGAR ON THE GROWTH OF BIFIDOBACTERIUM SPP. ON RAFFINOSE-BIFIDOBACTERIUM (RB) AGAR

The Swiss Ordinance on Food-Stuffs decrees that sour milk products sup plemented with bifidobacteria must contain at least 10(6) living organ isms per gram. The recently developed Raffinose-Bifidobacterium (RB) a gar was evaluated as an instrument for the control of this minimal req uirement. Quantitative analyses of products from the market have shown RB-agar to have promising attributes for control purposes. Colonies o f bifidobacteria could be rapidly and unmistakably counted. Preconditi on for true quantification was however, that an adequat agar-agar was used to solidify the test medium. It could be shown that certain agar- agar formulations partially inhibit the target organism. Presumably, f actors such as the selective agent in RB-agar and metabolites in sour milk products contribute to the inhibition phenomenon. The obtained re sults indicate that in the validation of bacteriological methods, agar -agar has to be kept in mind as possible source of inhibiting factors.