Prevalence analysis on probiotic stability In commercially available yogurts in Sri Lanka

Abstract

Probiotics have been defined as live food supplements which benefit the health ofthe consumer when administered in adequate amounts. Probiotics in the form of Lactobacillus bulgaricus and Streptococcus thermophilus in fermented yogurts have been ingested by humans for thousands of years. However, the viability of these bacteria is important in order to gain health benefits. The probiotic stability of the commercially available yogurts has been investigated in this study. Yogurt samples were collected from the market hit different brands i.e. A, B, C, D, E, F, G and H in different areas from Sri Lanka. The pH variation with the viability of probiotic bacteria and the bacterial count during its shelf life of yogurt were recorded. MRS and M17 agar were used to enumerate Lactobacillus bulgaricus and Streptococcus thermophilus respectively. The pH values decreased significantly (P < 0.05) from the production day to the end of storage period. Probiotic value has been evaluated by considering the counts of MRS and M17. International Dairy Federation (IDF) has been suggested the viability of probiotic bacteria should be at least 10⁶ cfuml⁻¹ to get its minimum therapeutic benefits. However, four out of eight products were contained over 10⁶ cfuml⁻¹of Lactobacillus bulgaricus on the production day to the seventh day. Only two of these products were maintained 10⁶ cfuml⁻¹ viable count of Lactobacillus bulgaricus till the end of the expiry. One was not reached 10⁶ cfuml⁻¹until the seventh day but it has reached to 10⁶ cfuml⁻¹ at the end of the expiry day. Conversely, all products showed the highest number of Streptococcus thermophilus (above 10⁸ cfuml⁻¹) within a week and two were reduced it is viable count up to 10⁷ cfuml⁻¹ . For optimum benefits, in general the probiotic yogurt products should be consumed within fourteen days from its manufacturing date. Studies have shown low viability of probiotics in marketed preparations and out of eight yogurt brands only three were maintaining above 10⁶ cfuml⁻¹ viable count of both probiotics within their expiry .