Microbial Analysis And Shelf Life Of Laboratory And Commercially Produced Yoghurt...

ABSTRACT

The microbial quality and shelf life of laboratory and commercially produced yoghurt were investigated. Six (6) laboratory prepared yoghurt, unsweetened (420) sweetened (421), unsweetened with sodium benzoate (422),sweetened with sodium benzoate(423), unsweetened with ginger (424), sweetened with ginger (425) and three (3) commercially produced yoghurt, Raph yoghurt (426) Nutri yo yoghurt (427) and Hollandia yoghurt (428) were used for this study. The bacterial genera; Lactobacillus acidophilus, Lactobacillus bulgaricus and Streptococcus thermophilus and three fungal genera Saccharomyces cerevisae, Saccharomyces lactis and Pichia spp. were isolated. The Total Viable Count (TVC) ranged from 3.0 x 108 cfulml to 2.4810 cfulml. The Total Fungal Count (TFC) ranged from 4.0 x i07cfu/ml to 2.6 x 108 cfulml while the Total Lactobacillus Count (TLC) ranged from 2.6 x 108 cfulml to 2.30 x i09cfulml. A zero count was recorded for the Total Coliform Count (TCC) and the Total Staphylococcus Count (TSC). For the physiochemical parameters of the yoghurt samples the pH ranged from 4.02 ± 1.00 to 6.50 ± 0.48, Specific Gravity (SG) ranged from 0.6971 ± 1729 to 1.0751 ± 0.2051. The Total Titrable Acidity (TTA) ranged from 8.71 ± 2.96 to 17.80 ± 6.13, while the Total Soluble Solid (TSS) ranged from 5.70 ± 4.37 to 14.00 ± 3.93. The sensory gradually moved from liked extremely (1) on day 0 to neither liked nor disliked (5) on day 14, even though the general acceptability stopped at liked slightly (4). The result of this study showed that refrigeration and deep freezing irrespective of the preservatives used prolonged the shelf life of yoghurt.