¹ - Dep. Natural Sciences, New Bulgarian University, 1618 Sofia, Montevideo str. 21

Lactobacillus bulgaricus, firstly discovered in 1905 by the Bulgarian physician Stamen Grigorov, cause lactic acid fermentation. L. bulgaricus possess antitoxic effects and in this relation the amount of lactobacteria in yogurt is crucial for the health effect. The aim of our study was to assess the number of lactobacilli in some of the often bought trade mark yougurts - LB, Parshevitsa and Rodopeia. Yogurts were purchased from large supermarkets. Analyzes were performed using the selective MRS media. The number of lactobacilli was evaluated by Koch’s method on agar media. The recorded experimental data showed that LB yogurt contain 7.1x10⁷, Parshevitza yogurt - 2.8x10⁷ and Rodopeia yogurt – 0.4x10⁷ lactobacilli. Our results demonstrated the highest count of lactobacilli in LB, followed by Parshevitza and Rodopeia yogurt. Several lactobacterial cultures were isolated and will be further indentified using API test.

Key words: lactobacteria; fabricated yougurt, MRS media