Yogurt has been a traditional food for Bulgarians for thousands of years. The discovery of this unique and nutritious product is attributed to the Thracian tribes who inhabited the lands of Bulgaria.

The Proto-Bulgarians inherited the practice of consuming milk that had naturally soured from the Thracians.Sheep's milk, which was a staple food of the Thracian tribes, also played a specific role in shaping themicroflora of Bulgarian yogurt. Sheep's milk is considered a key factor in the formation and strengthening ofBulgarian yogurt as a distinctive lactic acid product.

In 1905, when the Bulgarian scientist Stamen Grigorov discovered the microflora of Bulgarian yogurt, scientificre search and the search for possibilities for industrial production began.Initially, yogurt was produced by boiling milk in cauldrons, then cooling it, treating it with starters, and pouring it into 5-liter aluminum basins and 1-liter glass jars.

The start of industrial production came in 1960 at the "Serdica" dairy processing plant in Sofia, with the introduction of mechanized pasteurization of milk, though the use of aluminum basins continued. In 1966-1967, a new yogurt production workshop was built at "Serdica," and machines for automatically filling yogurt into glass jars and sealing them with aluminum foil were imported from England.

The beginning of the industrial production was in 1960 in dairy processing plant “Serdica” – Sofia, by introducing mechanized pasteurization of milk but the utilization of aluminium basins remains. In 1966-1967 in “Serdica” there was constructed a new workshop for yoghurt production. Machines for automatic filling of the yoghourt into glass jars and sealing with aluminium foil were imported from England.

The industrial production of yogurt was also introduced at other dairy processing plants across the country,but the products differed somewhat from those made at home. The main issues included a sharper taste thandesired, a grainy texture, and more pronounced syneresis. Additionally, the desired balance between Lactobacillus bulgaricus and Streptococcus thermophilus was often disrupted.

To address these issues, Professor Toniu Girginov conducted extensive research at the Institute of Food, Wine,and Tobacco Industries in Plovdiv (now the University of Food Technologies in Plovdiv) and developed an original technology for the industrial production of Bulgarian yogurt, based on four fundamental principles:

• The use of freshly prepared starter cultures for yogurt, containing active strains of Lactobacillus bulgaricusand Streptococcus thermophilus.
• Fermentation of milk at two different temperature regimes.
• Two-stage cooling of the milk.
• Continuous self-acidification of milk, combined with cooling in liquid form and maturation at 34°C orwithout cooling at 22-24°C.

To support this technology with starter cultures, the Central Laboratory of Pure Cultures in Sofia created seven symbiotic starter cultures for yogurt, which were patented and quickly implemented in production.

Yogurt produced using this technology, with the original Bulgarian starter cultures, has a typical taste and aroma, a homogeneous texture, and a dense consistency. This technology and the starter cultures quickly gained widespread use across all dairy processing plants in the country, where they continue to be used to this day.