These factors included strain used,

These factors included strain used, interaction
between species present, culture conditions, production of H2O2
due to bacterial metabolism, final acidity of the product, concentration
of lactic and acetic acids, availability of nutrients, growth
promoters and inhibitors, concentration of sugar (an osmotic
pressure effect), dissolved oxygen and oxygen permeation through
the package (especially for Bifidobacterium sp.), inoculation level,
incubation temperature, fermentation time and storage temperature
(Gregurek, 1999).