fermentation is a wonderous thing
some times there is only one fermentation
and sometimes there is a secondary fermentation even tertiary one
what results is sometimes a far cry different from the initial fermentation
take wine and vinegar
bread and sourdough
the primary fermentation breaks down one sugar or protien
once that is done the bacteria dies but leaves behind food for another type of bacteria to come along and continue breaking down the food
usually with dairy products i have noticed that a pinkish mold develops on old sour cream, buttermilk, yoghurt.........