Abstract

Investigation on the microbial safety and probiotic potentials of different yoghurt brands sold in Owerri, Imo State Nigeria, was carried out using standard microbiological procedures. Ten each, of five different brands of commercially available yoghurt packaged in plastic containers were purchased from the street vendors and shopping malls in Owerri metropolis. The mean total count of samples on Brain Heart Infusion (BHI) and De Mann Rogosa Sharpe (MRS) agar media ranged from 2.0×10⁷ to 6.0×10⁸ and 1.0×10⁸ to 5.4 × 10⁸ cfu/ml respectively. The yoghurt isolates were identified as Streptococcus and Lactobacillus species; these isolates were resistant to commonly used antibiotics and inhibited the growth of Staphylococcus aureusand Pseudomonas aeruginosa from clinical samples. No viable growth of isolates was observed in simulated gastric fluid of pH 1.5 to 2.5. Slight decrease in viable count ofLactobacillus spp. from 4.0×10⁷ to 3.0×10⁷ cfu/ml and Streptococcus spp. from 3.0×10⁸ to 2.0×10⁸ cfu/ml was observed in bile of pH 8.28 to 8.30. The isolates were recovered from faecal samples two weeks after ingestion with mean count ranging from no growth (zero) to 5.8×10⁸ cfu/ml on MRS agar media. The isolates were found to exhibit some probiotic potentials and no pathogen was isolated from samples. It is recommended that strains of microorganisms that can deliver full probiotic potentials to consumers be used in commercial yoghurt production.

Key words: Yoghurt, microbial safety, probiotic potential, simulated gastric fluid, bile.