Quantitative analysis of Lactobacillus bulgaricus in commercially available yogurts “Vereya”, “Na Baba” and “Elena”

Mincheva M.¹, Doycheva A.¹ and G. Satchanska¹

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

Lactobacillus delbrueckii subsp. bulgaricus together with Streptococcus thermophilus is responsible for the fermentation of the bulgarian yogurt. The cells are rod-shaped, often arranged in chains containing metachromatic granules. It synthesizes beta-galactosidase in highest amount among the other lactobacilli. The aim of our experiments was to study the number of lactobacilli in three 3.6 % cow yogurt samples – “Vereya”, “Na baba” and “Elena”, commercially available in Bulgaria. The experiments were conducted with 1 g yogurt via the Koch’s method - tenfold serial dilutions spread on MRS agar. Incubation was performed at 45^o C for 24 h. The experimental data showed the following count of L. bulgaricus per 1 gram yogurt – “Vereia” – 2.6x10⁶, “Na baba” - 3.4x10⁶ and “Elena” - 0,7x10⁶. According to the Bulgarian State Standard (BDS) the count of L. bulgaricus per gram yogurt is necessary to be 1x10⁶ to 1x10⁷. Our results revealed that both yogurt products “Na baba” and “Vereya” cover BDS. Elena yogurt is close to the standard. Based on these results we conclude that the examined yogurt products are appropriate for consumption and could express their healthful effect on customers.

Key words: Lactobacillus bulgaricus, commercially available yogurt, count, MRS