Milk is sweetened and wine is spoiled by homolactic bacteria. You inoculate a chemically defined media that is lacking vitamin B12 with a fastidious bacteria that requires vitamin B12. The lag phase in bacterial growth has very little metabolic activity within the bacteria. The lag phase has very little duplication of bacteria. The stationary phase is where the bacteria stop growing in order to rest.
Bacteria can take as little as a few hours to reach their maximum numbers.