This invention discloses novel methods of making fermented food products such as yogurt. It also discloses novel Lactobacillus bulgaricus organisms for making fermented food products which are conditionally sensitive, that is, operate to metabolize a desired compound normally under the processing conditions for fermented food products but slow or decrease in activity beyond what is normal under the routine storage temperatures for the fermented food products. Such fermented food products exhibit improved shelf life and long-term taste.