In the present work the use of 14C-labelled lactose in order to
determine lactose uptake rate by cells was a very convenient laboratory
method as labelled and unlabelled lactose molecules follow
the same metabolic pathways. So, the relation between kefir
fermentation ability and carbohydrate uptake rate by kefir cells
was really clarified by the 14C-labelled lactose determination during
whey fermentation.