These two compounds would consequently provide for the enhanced growth of Lb. bulgaricus, and the bulk of acid toward the end of fermentation is produced by this organism. High concentration of lactic acid favors Lb. bulgaricus due to its acidophilic nature,but it also adversely affects St. thermophilus, whose growth would eventually seize. The overproduction of acids during storage may lead to a defect commonly referred to as post-acidification