BULGARIAN YOGURT Bulgarian yogurt is a fermented milk product. In common with all dairy yogurt, Bulgarian yogurt is produced through the bacterial fermentation of milk, using a live culture of Lactobacillus bulgaricus and Streptococcus thermophilus. Fermentation ends when the yogurt has cooled. The longer the yogurt is allowed to stay warm, the more pronounced the sour flavor becomes. Bulgarian yogurt is similar to other yogurt produced in the Balkans, but it has a distinctive flavor. This is due to the milk of the Bulgarian sheep, which are raised on herb-rich pastures using traditional methods, and to the specific local strains of bacteria used. Another factor influencing flavor is that Bulgarian yogurt is never sterilized after fermentation.